The ALSA Driver API¶

Management of Cards and Devices¶

Card Management¶

int snd_device_alloc(struct device **dev_p, struct snd_card *card)¶: Allocate and initialize struct device for sound devices

Parameters

struct device **dev_p: pointer to store the allocated device
struct snd_card *card: card to assign, optional

Description

For releasing the allocated device, call put_device().

int snd_card_new(struct device *parent, int idx, const char *xid, struct module *module, int extra_size, struct snd_card **card_ret)¶: create and initialize a soundcard structure

Parameters

struct device *parent

the parent device object

int idx

card index (address) [0 ... (SNDRV_CARDS-1)]

const char *xid

card identification (ASCII string)

struct module *module

top level module for locking

int extra_size

allocate this extra size after the main soundcard structure

struct snd_card **card_ret

the pointer to store the created card instance

The function allocates snd_card instance via kzalloc with the given space for the driver to use freely. The allocated struct is stored in the given card_ret pointer.

Return

Zero if successful or a negative error code.

int snd_devm_card_new(struct device *parent, int idx, const char *xid, struct module *module, size_t extra_size, struct snd_card **card_ret)¶: managed snd_card object creation

Parameters

struct device *parent: the parent device object
int idx: card index (address) [0 ... (SNDRV_CARDS-1)]
const char *xid: card identification (ASCII string)
struct module *module: top level module for locking
size_t extra_size: allocate this extra size after the main soundcard structure
struct snd_card **card_ret: the pointer to store the created card instance

Description

This function works like snd_card_new() but manages the allocated resource via devres, i.e. you don’t need to free explicitly.

When a snd_card object is created with this function and registered via snd_card_register(), the very first devres action to call snd_card_free() is added automatically. In that way, the resource disconnection is assured at first, then released in the expected order.

If an error happens at the probe before snd_card_register() is called and there have been other devres resources, you’d need to free the card manually via snd_card_free() call in the error; otherwise it may lead to UAF due to devres call orders. You can use snd_card_free_on_error() helper for handling it more easily.

Return

zero if successful, or a negative error code

int snd_card_free_on_error(struct device *dev, int ret)¶: a small helper for handling devm probe errors

Parameters

struct device *dev: the managed device object
int ret: the return code from the probe callback

Description

This function handles the explicit snd_card_free() call at the error from the probe callback. It’s just a small helper for simplifying the error handling with the managed devices.

Return

zero if successful, or a negative error code

struct snd_card *snd_card_ref(int idx)¶: Get the card object from the index

Parameters

int idx: the card index

Description

Returns a card object corresponding to the given index or NULL if not found. Release the object via snd_card_unref().

Return

a card object or NULL

void snd_card_disconnect(struct snd_card *card)¶: disconnect all APIs from the file-operations (user space)

Parameters

struct snd_card *card

soundcard structure

Disconnects all APIs from the file-operations (user space).

Return

Zero, otherwise a negative error code.

Note

The current implementation replaces all active file->f_op with special: dummy file operations (they do nothing except release).

void snd_card_disconnect_sync(struct snd_card *card)¶: disconnect card and wait until files get closed

Parameters

struct snd_card *card: card object to disconnect

Description

This calls snd_card_disconnect() for disconnecting all belonging components and waits until all pending files get closed. It assures that all accesses from user-space finished so that the driver can release its resources gracefully.

void snd_card_free_when_closed(struct snd_card *card)¶: Disconnect the card, free it later eventually

Parameters

struct snd_card *card: soundcard structure

Description

Unlike snd_card_free(), this function doesn’t try to release the card resource immediately, but tries to disconnect at first. When the card is still in use, the function returns before freeing the resources. The card resources will be freed when the refcount gets to zero.

Return

zero if successful, or a negative error code

void snd_card_free(struct snd_card *card)¶: frees given soundcard structure

Parameters

struct snd_card *card: soundcard structure

Description

This function releases the soundcard structure and the all assigned devices automatically. That is, you don’t have to release the devices by yourself.

This function waits until the all resources are properly released.

Return

Zero. Frees all associated devices and frees the control interface associated to given soundcard.

void snd_card_set_id(struct snd_card *card, const char *nid)¶: set card identification name

Parameters

struct snd_card *card

soundcard structure

const char *nid

new identification string

This function sets the card identification and checks for name collisions.

int snd_card_add_dev_attr(struct snd_card *card, const struct attribute_group *group)¶: Append a new sysfs attribute group to card

Parameters

struct snd_card *card: card instance
const struct attribute_group *group: attribute group to append

Return

zero if successful, or a negative error code

int snd_card_register(struct snd_card *card)¶: register the soundcard

Parameters

struct snd_card *card

soundcard structure

This function registers all the devices assigned to the soundcard. Until calling this, the ALSA control interface is blocked from the external accesses. Thus, you should call this function at the end of the initialization of the card.

Return

Zero otherwise a negative error code if the registration failed.

int snd_component_add(struct snd_card *card, const char *component)¶: add a component string

Parameters

struct snd_card *card

soundcard structure

const char *component

the component id string

This function adds the component id string to the supported list. The component can be referred from the alsa-lib.

Return

Zero otherwise a negative error code.

int snd_card_file_add(struct snd_card *card, struct file *file)¶: add the file to the file list of the card

Parameters

struct snd_card *card

soundcard structure

struct file *file

file pointer

This function adds the file to the file linked-list of the card. This linked-list is used to keep tracking the connection state, and to avoid the release of busy resources by hotplug.

Return

zero or a negative error code.

int snd_card_file_remove(struct snd_card *card, struct file *file)¶: remove the file from the file list

Parameters

struct snd_card *card

soundcard structure

struct file *file

file pointer

This function removes the file formerly added to the card via snd_card_file_add() function. If all files are removed and snd_card_free_when_closed() was called beforehand, it processes the pending release of resources.

Return

Zero or a negative error code.

int snd_power_ref_and_wait(struct snd_card *card)¶: wait until the card gets powered up

Parameters

struct snd_card *card: soundcard structure

Description

Take the power_ref reference count of the given card, and wait until the card gets powered up to SNDRV_CTL_POWER_D0 state. The refcount is down again while sleeping until power-up, hence this function can be used for syncing the floating control ops accesses, typically around calling control ops.

The caller needs to pull down the refcount via snd_power_unref() later no matter whether the error is returned from this function or not.

Return

Zero if successful, or a negative error code.

int snd_power_wait(struct snd_card *card)¶: wait until the card gets powered up (old form)

Parameters

struct snd_card *card: soundcard structure

Description

Wait until the card gets powered up to SNDRV_CTL_POWER_D0 state.

Return

Zero if successful, or a negative error code.

Device Components¶

int snd_device_new(struct snd_card *card, enum snd_device_type type, void *device_data, const struct snd_device_ops *ops)¶: create an ALSA device component

Parameters

struct snd_card *card: the card instance
enum snd_device_type type: the device type, SNDRV_DEV_XXX
void *device_data: the data pointer of this device
const struct snd_device_ops *ops: the operator table

Description

Creates a new device component for the given data pointer. The device will be assigned to the card and managed together by the card.

The data pointer plays a role as the identifier, too, so the pointer address must be unique and unchanged.

Return

Zero if successful, or a negative error code on failure.

void snd_device_disconnect(struct snd_card *card, void *device_data)¶: disconnect the device

Parameters

struct snd_card *card: the card instance
void *device_data: the data pointer to disconnect

Description

Turns the device into the disconnection state, invoking dev_disconnect callback, if the device was already registered.

Usually called from snd_card_disconnect().

Return

Zero if successful, or a negative error code on failure or if the device not found.

void snd_device_free(struct snd_card *card, void *device_data)¶: release the device from the card

Parameters

struct snd_card *card: the card instance
void *device_data: the data pointer to release

Description

Removes the device from the list on the card and invokes the callbacks, dev_disconnect and dev_free, corresponding to the state. Then release the device.

int snd_device_register(struct snd_card *card, void *device_data)¶: register the device

Parameters

struct snd_card *card: the card instance
void *device_data: the data pointer to register

Description

Registers the device which was already created via snd_device_new(). Usually this is called from snd_card_register(), but it can be called later if any new devices are created after invocation of snd_card_register().

Return

Zero if successful, or a negative error code on failure or if the device not found.

int snd_device_get_state(struct snd_card *card, void *device_data)¶: Get the current state of the given device

Parameters

struct snd_card *card: the card instance
void *device_data: the data pointer to release

Description

Returns the current state of the given device object. For the valid device, either SNDRV_DEV_BUILD, SNDRV_DEV_REGISTERED or SNDRV_DEV_DISCONNECTED is returned. Or for a non-existing device, -1 is returned as an error.

Return

the current state, or -1 if not found

Module requests and Device File Entries¶

void snd_request_card(int card)¶: try to load the card module

Parameters

int card: the card number

Description

Tries to load the module “snd-card-X” for the given card number via request_module. Returns immediately if already loaded.

void *snd_lookup_minor_data(unsigned int minor, int type)¶: get user data of a registered device

Parameters

unsigned int minor: the minor number
int type: device type (SNDRV_DEVICE_TYPE_XXX)

Description

Checks that a minor device with the specified type is registered, and returns its user data pointer.

This function increments the reference counter of the card instance if an associated instance with the given minor number and type is found. The caller must call snd_card_unref() appropriately later.

Return

The user data pointer if the specified device is found. NULL otherwise.

int snd_register_device(int type, struct snd_card *card, int dev, const struct file_operations *f_ops, void *private_data, struct device *device)¶: Register the ALSA device file for the card

Parameters

int type: the device type, SNDRV_DEVICE_TYPE_XXX
struct snd_card *card: the card instance
int dev: the device index
const struct file_operations *f_ops: the file operations
void *private_data: user pointer for f_ops->open()
struct device *device: the device to register

Description

Registers an ALSA device file for the given card. The operators have to be set in reg parameter.

Return

Zero if successful, or a negative error code on failure.

int snd_unregister_device(struct device *dev)¶: unregister the device on the given card

Parameters

struct device *dev: the device instance

Description

Unregisters the device file already registered via snd_register_device().

Return

Zero if successful, or a negative error code on failure.

Memory Management Helpers¶

int copy_to_user_fromio(void __user *dst, volatile const void __iomem *src, size_t count)¶: copy data from mmio-space to user-space

Parameters

void __user *dst: the destination pointer on user-space
const volatile void __iomem *src: the source pointer on mmio
size_t count: the data size to copy in bytes

Description

Copies the data from mmio-space to user-space.

Return

Zero if successful, or non-zero on failure.

int copy_to_iter_fromio(struct iov_iter *dst, const void __iomem *src, size_t count)¶: copy data from mmio-space to iov_iter

Parameters

struct iov_iter *dst: the destination iov_iter
const void __iomem *src: the source pointer on mmio
size_t count: the data size to copy in bytes

Description

Copies the data from mmio-space to iov_iter.

Return

Zero if successful, or non-zero on failure.

int copy_from_user_toio(volatile void __iomem *dst, const void __user *src, size_t count)¶: copy data from user-space to mmio-space

Parameters

volatile void __iomem *dst: the destination pointer on mmio-space
const void __user *src: the source pointer on user-space
size_t count: the data size to copy in bytes

Description

Copies the data from user-space to mmio-space.

Return

Zero if successful, or non-zero on failure.

int copy_from_iter_toio(void __iomem *dst, struct iov_iter *src, size_t count)¶: copy data from iov_iter to mmio-space

Parameters

void __iomem *dst: the destination pointer on mmio-space
struct iov_iter *src: the source iov_iter
size_t count: the data size to copy in bytes

Description

Copies the data from iov_iter to mmio-space.

Return

Zero if successful, or non-zero on failure.

int snd_dma_alloc_dir_pages(int type, struct device *device, enum dma_data_direction dir, size_t size, struct snd_dma_buffer *dmab)¶: allocate the buffer area according to the given type and direction

Parameters

int type: the DMA buffer type
struct device *device: the device pointer
enum dma_data_direction dir: DMA direction
size_t size: the buffer size to allocate
struct snd_dma_buffer *dmab: buffer allocation record to store the allocated data

Description

Calls the memory-allocator function for the corresponding buffer type.

Return

Zero if the buffer with the given size is allocated successfully, otherwise a negative value on error.

int snd_dma_alloc_pages_fallback(int type, struct device *device, size_t size, struct snd_dma_buffer *dmab)¶: allocate the buffer area according to the given type with fallback

Parameters

int type: the DMA buffer type
struct device *device: the device pointer
size_t size: the buffer size to allocate
struct snd_dma_buffer *dmab: buffer allocation record to store the allocated data

Description

Calls the memory-allocator function for the corresponding buffer type. When no space is left, this function reduces the size and tries to allocate again. The size actually allocated is stored in res_size argument.

Return

Zero if the buffer with the given size is allocated successfully, otherwise a negative value on error.

void snd_dma_free_pages(struct snd_dma_buffer *dmab)¶: release the allocated buffer

Parameters

struct snd_dma_buffer *dmab: the buffer allocation record to release

Description

Releases the allocated buffer via snd_dma_alloc_pages().

struct snd_dma_buffer *snd_devm_alloc_dir_pages(struct device *dev, int type, enum dma_data_direction dir, size_t size)¶: allocate the buffer and manage with devres

Parameters

struct device *dev: the device pointer
int type: the DMA buffer type
enum dma_data_direction dir: DMA direction
size_t size: the buffer size to allocate

Description

Allocate buffer pages depending on the given type and manage using devres. The pages will be released automatically at the device removal.

Unlike snd_dma_alloc_pages(), this function requires the real device pointer, hence it can’t work with SNDRV_DMA_TYPE_CONTINUOUS or SNDRV_DMA_TYPE_VMALLOC type.

Return

the snd_dma_buffer object at success, or NULL if failed

int snd_dma_buffer_mmap(struct snd_dma_buffer *dmab, struct vm_area_struct *area)¶: perform mmap of the given DMA buffer

Parameters

struct snd_dma_buffer *dmab: buffer allocation information
struct vm_area_struct *area: VM area information

Return

zero if successful, or a negative error code

void snd_dma_buffer_sync(struct snd_dma_buffer *dmab, enum snd_dma_sync_mode mode)¶: sync DMA buffer between CPU and device

Parameters

struct snd_dma_buffer *dmab: buffer allocation information
enum snd_dma_sync_mode mode: sync mode

dma_addr_t snd_sgbuf_get_addr(struct snd_dma_buffer *dmab, size_t offset)¶: return the physical address at the corresponding offset

Parameters

struct snd_dma_buffer *dmab: buffer allocation information
size_t offset: offset in the ring buffer

Return

the physical address

struct page *snd_sgbuf_get_page(struct snd_dma_buffer *dmab, size_t offset)¶: return the physical page at the corresponding offset

Parameters

struct snd_dma_buffer *dmab: buffer allocation information
size_t offset: offset in the ring buffer

Return

the page pointer

unsigned int snd_sgbuf_get_chunk_size(struct snd_dma_buffer *dmab, unsigned int ofs, unsigned int size)¶: compute the max chunk size with continuous pages on sg-buffer

Parameters

struct snd_dma_buffer *dmab: buffer allocation information
unsigned int ofs: offset in the ring buffer
unsigned int size: the requested size

Return

the chunk size

PCM API¶

PCM Core¶

const char *snd_pcm_format_name(snd_pcm_format_t format)¶: Return a name string for the given PCM format

Parameters

snd_pcm_format_t format: PCM format

Return

the format name string

int snd_pcm_new_stream(struct snd_pcm *pcm, int stream, int substream_count)¶: create a new PCM stream

Parameters

struct snd_pcm *pcm: the pcm instance
int stream: the stream direction, SNDRV_PCM_STREAM_XXX
int substream_count: the number of substreams

Description

Creates a new stream for the pcm. The corresponding stream on the pcm must have been empty before calling this, i.e. zero must be given to the argument of snd_pcm_new().

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_new(struct snd_card *card, const char *id, int device, int playback_count, int capture_count, struct snd_pcm **rpcm)¶: create a new PCM instance

Parameters

struct snd_card *card: the card instance
const char *id: the id string
int device: the device index (zero based)
int playback_count: the number of substreams for playback
int capture_count: the number of substreams for capture
struct snd_pcm **rpcm: the pointer to store the new pcm instance

Description

Creates a new PCM instance.

The pcm operators have to be set afterwards to the new instance via snd_pcm_set_ops().

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_new_internal(struct snd_card *card, const char *id, int device, int playback_count, int capture_count, struct snd_pcm **rpcm)¶: create a new internal PCM instance

Parameters

struct snd_card *card: the card instance
const char *id: the id string
int device: the device index (zero based - shared with normal PCMs)
int playback_count: the number of substreams for playback
int capture_count: the number of substreams for capture
struct snd_pcm **rpcm: the pointer to store the new pcm instance

Description

Creates a new internal PCM instance with no userspace device or procfs entries. This is used by ASoC Back End PCMs in order to create a PCM that will only be used internally by kernel drivers. i.e. it cannot be opened by userspace. It provides existing ASoC components drivers with a substream and access to any private data.

The pcm operators have to be set afterwards to the new instance via snd_pcm_set_ops().

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_notify(struct snd_pcm_notify *notify, int nfree)¶: Add/remove the notify list

Parameters

struct snd_pcm_notify *notify: PCM notify list
int nfree: 0 = register, 1 = unregister

Description

This adds the given notifier to the global list so that the callback is called for each registered PCM devices. This exists only for PCM OSS emulation, so far.

Return

zero if successful, or a negative error code

void snd_pcm_set_ops(struct snd_pcm *pcm, int direction, const struct snd_pcm_ops *ops)¶: set the PCM operators

Parameters

struct snd_pcm *pcm: the pcm instance
int direction: stream direction, SNDRV_PCM_STREAM_XXX
const struct snd_pcm_ops *ops: the operator table

Description

Sets the given PCM operators to the pcm instance.

void snd_pcm_set_sync_per_card(struct snd_pcm_substream *substream, struct snd_pcm_hw_params *params, const unsigned char *id, unsigned int len)¶: set the PCM sync id with card number

Parameters

struct snd_pcm_substream *substream: the pcm substream
struct snd_pcm_hw_params *params: modified hardware parameters
const unsigned char *id: identifier (max 12 bytes)
unsigned int len: identifier length (max 12 bytes)

Description

Sets the PCM sync identifier for the card with zero padding.

User space or any user should use this 16-byte identifier for a comparison only to check if two IDs are similar or different. Special case is the identifier containing only zeros. Interpretation for this combination is - empty (not set). The contents of the identifier should not be interpreted in any other way.

The synchronization ID must be unique per clock source (usually one sound card, but multiple soundcard may use one PCM word clock source which means that they are fully synchronized).

This routine composes this ID using card number in first four bytes and 12-byte additional ID. When other ID composition is used (e.g. for multiple sound cards), make sure that the composition does not clash with this composition scheme.

int snd_interval_refine(struct snd_interval *i, const struct snd_interval *v)¶: refine the interval value of configurator

Parameters

struct snd_interval *i: the interval value to refine
const struct snd_interval *v: the interval value to refer to

Description

Refines the interval value with the reference value. The interval is changed to the range satisfying both intervals. The interval status (min, max, integer, etc.) are evaluated.

Return

Positive if the value is changed, zero if it’s not changed, or a negative error code.

void snd_interval_div(const struct snd_interval *a, const struct snd_interval *b, struct snd_interval *c)¶: refine the interval value with division

Parameters

const struct snd_interval *a: dividend
const struct snd_interval *b: divisor
struct snd_interval *c: quotient

Description

c = a / b

Returns non-zero if the value is changed, zero if not changed.

void snd_interval_muldivk(const struct snd_interval *a, const struct snd_interval *b, unsigned int k, struct snd_interval *c)¶: refine the interval value

Parameters

const struct snd_interval *a: dividend 1
const struct snd_interval *b: dividend 2
unsigned int k: divisor (as integer)
struct snd_interval *c: result

Description

c = a * b / k

Returns non-zero if the value is changed, zero if not changed.

void snd_interval_mulkdiv(const struct snd_interval *a, unsigned int k, const struct snd_interval *b, struct snd_interval *c)¶: refine the interval value

Parameters

const struct snd_interval *a: dividend 1
unsigned int k: dividend 2 (as integer)
const struct snd_interval *b: divisor
struct snd_interval *c: result

Description

c = a * k / b

Returns non-zero if the value is changed, zero if not changed.

int snd_interval_ratnum(struct snd_interval *i, unsigned int rats_count, const struct snd_ratnum *rats, unsigned int *nump, unsigned int *denp)¶: refine the interval value

Parameters

struct snd_interval *i: interval to refine
unsigned int rats_count: number of ratnum_t
const struct snd_ratnum *rats: ratnum_t array
unsigned int *nump: pointer to store the resultant numerator
unsigned int *denp: pointer to store the resultant denominator

Return

Positive if the value is changed, zero if it’s not changed, or a negative error code.

int snd_interval_ratden(struct snd_interval *i, unsigned int rats_count, const struct snd_ratden *rats, unsigned int *nump, unsigned int *denp)¶: refine the interval value

Parameters

struct snd_interval *i: interval to refine
unsigned int rats_count: number of struct ratden
const struct snd_ratden *rats: struct ratden array
unsigned int *nump: pointer to store the resultant numerator
unsigned int *denp: pointer to store the resultant denominator

Return

Positive if the value is changed, zero if it’s not changed, or a negative error code.

int snd_interval_list(struct snd_interval *i, unsigned int count, const unsigned int *list, unsigned int mask)¶: refine the interval value from the list

Parameters

struct snd_interval *i: the interval value to refine
unsigned int count: the number of elements in the list
const unsigned int *list: the value list
unsigned int mask: the bit-mask to evaluate

Description

Refines the interval value from the list. When mask is non-zero, only the elements corresponding to bit 1 are evaluated.

Return

Positive if the value is changed, zero if it’s not changed, or a negative error code.

int snd_interval_ranges(struct snd_interval *i, unsigned int count, const struct snd_interval *ranges, unsigned int mask)¶: refine the interval value from the list of ranges

Parameters

struct snd_interval *i: the interval value to refine
unsigned int count: the number of elements in the list of ranges
const struct snd_interval *ranges: the ranges list
unsigned int mask: the bit-mask to evaluate

Description

Refines the interval value from the list of ranges. When mask is non-zero, only the elements corresponding to bit 1 are evaluated.

Return

Positive if the value is changed, zero if it’s not changed, or a negative error code.

int snd_pcm_hw_rule_add(struct snd_pcm_runtime *runtime, unsigned int cond, int var, snd_pcm_hw_rule_func_t func, void *private, int dep, ...)¶: add the hw-constraint rule

Parameters

struct snd_pcm_runtime *runtime: the pcm runtime instance
unsigned int cond: condition bits
int var: the variable to evaluate
snd_pcm_hw_rule_func_t func: the evaluation function
void *private: the private data pointer passed to function
int dep: the dependent variables
...: variable arguments

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_mask(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var, u_int32_t mask)¶: apply the given bitmap mask constraint

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
snd_pcm_hw_param_t var: hw_params variable to apply the mask
u_int32_t mask: the bitmap mask

Description

Apply the constraint of the given bitmap mask to a 32-bit mask parameter.

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_mask64(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var, u_int64_t mask)¶: apply the given bitmap mask constraint

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
snd_pcm_hw_param_t var: hw_params variable to apply the mask
u_int64_t mask: the 64bit bitmap mask

Description

Apply the constraint of the given bitmap mask to a 64-bit mask parameter.

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_integer(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var)¶: apply an integer constraint to an interval

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
snd_pcm_hw_param_t var: hw_params variable to apply the integer constraint

Description

Apply the constraint of integer to an interval parameter.

Return

Positive if the value is changed, zero if it’s not changed, or a negative error code.

int snd_pcm_hw_constraint_minmax(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var, unsigned int min, unsigned int max)¶: apply a min/max range constraint to an interval

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
snd_pcm_hw_param_t var: hw_params variable to apply the range
unsigned int min: the minimal value
unsigned int max: the maximal value

Description

Apply the min/max range constraint to an interval parameter.

Return

Positive if the value is changed, zero if it’s not changed, or a negative error code.

int snd_pcm_hw_constraint_list(struct snd_pcm_runtime *runtime, unsigned int cond, snd_pcm_hw_param_t var, const struct snd_pcm_hw_constraint_list *l)¶: apply a list of constraints to a parameter

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
unsigned int cond: condition bits
snd_pcm_hw_param_t var: hw_params variable to apply the list constraint
const struct snd_pcm_hw_constraint_list *l: list

Description

Apply the list of constraints to an interval parameter.

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_ranges(struct snd_pcm_runtime *runtime, unsigned int cond, snd_pcm_hw_param_t var, const struct snd_pcm_hw_constraint_ranges *r)¶: apply list of range constraints to a parameter

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
unsigned int cond: condition bits
snd_pcm_hw_param_t var: hw_params variable to apply the list of range constraints
const struct snd_pcm_hw_constraint_ranges *r: ranges

Description

Apply the list of range constraints to an interval parameter.

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_ratnums(struct snd_pcm_runtime *runtime, unsigned int cond, snd_pcm_hw_param_t var, const struct snd_pcm_hw_constraint_ratnums *r)¶: apply ratnums constraint to a parameter

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
unsigned int cond: condition bits
snd_pcm_hw_param_t var: hw_params variable to apply the ratnums constraint
const struct snd_pcm_hw_constraint_ratnums *r: struct snd_ratnums constriants

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_ratdens(struct snd_pcm_runtime *runtime, unsigned int cond, snd_pcm_hw_param_t var, const struct snd_pcm_hw_constraint_ratdens *r)¶: apply ratdens constraint to a parameter

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
unsigned int cond: condition bits
snd_pcm_hw_param_t var: hw_params variable to apply the ratdens constraint
const struct snd_pcm_hw_constraint_ratdens *r: struct snd_ratdens constriants

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_msbits(struct snd_pcm_runtime *runtime, unsigned int cond, unsigned int width, unsigned int msbits)¶: add a hw constraint msbits rule

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
unsigned int cond: condition bits
unsigned int width: sample bits width
unsigned int msbits: msbits width

Description

This constraint will set the number of most significant bits (msbits) if a sample format with the specified width has been select. If width is set to 0 the msbits will be set for any sample format with a width larger than the specified msbits.

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_step(struct snd_pcm_runtime *runtime, unsigned int cond, snd_pcm_hw_param_t var, unsigned long step)¶: add a hw constraint step rule

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
unsigned int cond: condition bits
snd_pcm_hw_param_t var: hw_params variable to apply the step constraint
unsigned long step: step size

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_constraint_pow2(struct snd_pcm_runtime *runtime, unsigned int cond, snd_pcm_hw_param_t var)¶: add a hw constraint power-of-2 rule

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
unsigned int cond: condition bits
snd_pcm_hw_param_t var: hw_params variable to apply the power-of-2 constraint

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_rule_noresample(struct snd_pcm_runtime *runtime, unsigned int base_rate)¶: add a rule to allow disabling hw resampling

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
unsigned int base_rate: the rate at which the hardware does not resample

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_param_value(const struct snd_pcm_hw_params *params, snd_pcm_hw_param_t var, int *dir)¶: return params field var value

Parameters

const struct snd_pcm_hw_params *params: the hw_params instance
snd_pcm_hw_param_t var: parameter to retrieve
int *dir: pointer to the direction (-1,0,1) or NULL

Return

The value for field var if it’s fixed in configuration space defined by params. -EINVAL otherwise.

int snd_pcm_hw_param_first(struct snd_pcm_substream *pcm, struct snd_pcm_hw_params *params, snd_pcm_hw_param_t var, int *dir)¶: refine config space and return minimum value

Parameters

struct snd_pcm_substream *pcm: PCM instance
struct snd_pcm_hw_params *params: the hw_params instance
snd_pcm_hw_param_t var: parameter to retrieve
int *dir: pointer to the direction (-1,0,1) or NULL

Description

Inside configuration space defined by params remove from var all values > minimum. Reduce configuration space accordingly.

Return

The minimum, or a negative error code on failure.

int snd_pcm_hw_param_last(struct snd_pcm_substream *pcm, struct snd_pcm_hw_params *params, snd_pcm_hw_param_t var, int *dir)¶: refine config space and return maximum value

Parameters

struct snd_pcm_substream *pcm: PCM instance
struct snd_pcm_hw_params *params: the hw_params instance
snd_pcm_hw_param_t var: parameter to retrieve
int *dir: pointer to the direction (-1,0,1) or NULL

Description

Inside configuration space defined by params remove from var all values < maximum. Reduce configuration space accordingly.

Return

The maximum, or a negative error code on failure.

int snd_pcm_hw_params_bits(const struct snd_pcm_hw_params *p)¶: Get the number of bits per the sample.

Parameters

const struct snd_pcm_hw_params *p: hardware parameters

Return

The number of bits per sample based on the format, subformat and msbits the specified hw params has.

int snd_pcm_lib_ioctl(struct snd_pcm_substream *substream, unsigned int cmd, void *arg)¶: a generic PCM ioctl callback

Parameters

struct snd_pcm_substream *substream: the pcm substream instance
unsigned int cmd: ioctl command
void *arg: ioctl argument

Description

Processes the generic ioctl commands for PCM. Can be passed as the ioctl callback for PCM ops.

Return

Zero if successful, or a negative error code on failure.

void snd_pcm_period_elapsed_under_stream_lock(struct snd_pcm_substream *substream)¶: update the status of runtime for the next period under acquired lock of PCM substream.

Parameters

struct snd_pcm_substream *substream: the instance of pcm substream.

Description

This function is called when the batch of audio data frames as the same size as the period of buffer is already processed in audio data transmission.

The call of function updates the status of runtime with the latest position of audio data transmission, checks overrun and underrun over buffer, awaken user processes from waiting for available audio data frames, sampling audio timestamp, and performs stop or drain the PCM substream according to configured threshold.

The function is intended to use for the case that PCM driver operates audio data frames under acquired lock of PCM substream; e.g. in callback of any operation of snd_pcm_ops in process context. In any interrupt context, it’s preferrable to use snd_pcm_period_elapsed() instead since lock of PCM substream should be acquired in advance.

Developer should pay enough attention that some callbacks in snd_pcm_ops are done by the call of function:

.pointer - to retrieve current position of audio data transmission by frame count or XRUN state.
.trigger - with SNDRV_PCM_TRIGGER_STOP at XRUN or DRAINING state.
.get_time_info - to retrieve audio time stamp if needed.

Even if more than one periods have elapsed since the last call, you have to call this only once.

void snd_pcm_period_elapsed(struct snd_pcm_substream *substream)¶: update the status of runtime for the next period by acquiring lock of PCM substream.

Parameters

struct snd_pcm_substream *substream: the instance of PCM substream.

Description

This function is mostly similar to snd_pcm_period_elapsed_under_stream_lock() except for acquiring lock of PCM substream voluntarily.

It’s typically called by any type of IRQ handler when hardware IRQ occurs to notify event that the batch of audio data frames as the same size as the period of buffer is already processed in audio data transmission.

int snd_pcm_add_chmap_ctls(struct snd_pcm *pcm, int stream, const struct snd_pcm_chmap_elem *chmap, int max_channels, unsigned long private_value, struct snd_pcm_chmap **info_ret)¶: create channel-mapping control elements

Parameters

struct snd_pcm *pcm: the assigned PCM instance
int stream: stream direction
const struct snd_pcm_chmap_elem *chmap: channel map elements (for query)
int max_channels: the max number of channels for the stream
unsigned long private_value: the value passed to each kcontrol’s private_value field
struct snd_pcm_chmap **info_ret: store struct snd_pcm_chmap instance if non-NULL

Description

Create channel-mapping control elements assigned to the given PCM stream(s).

Return

Zero if successful, or a negative error value.

void snd_pcm_stream_lock(struct snd_pcm_substream *substream)¶: Lock the PCM stream

Parameters

struct snd_pcm_substream *substream: PCM substream

Description

This locks the PCM stream’s spinlock or mutex depending on the nonatomic flag of the given substream. This also takes the global link rw lock (or rw sem), too, for avoiding the race with linked streams.

void snd_pcm_stream_unlock(struct snd_pcm_substream *substream)¶: Unlock the PCM stream

Parameters

struct snd_pcm_substream *substream: PCM substream

Description

This unlocks the PCM stream that has been locked via snd_pcm_stream_lock().

void snd_pcm_stream_lock_irq(struct snd_pcm_substream *substream)¶: Lock the PCM stream

Parameters

struct snd_pcm_substream *substream: PCM substream

Description

This locks the PCM stream like snd_pcm_stream_lock() and disables the local IRQ (only when nonatomic is false). In nonatomic case, this is identical as snd_pcm_stream_lock().

void snd_pcm_stream_unlock_irq(struct snd_pcm_substream *substream)¶: Unlock the PCM stream

Parameters

struct snd_pcm_substream *substream: PCM substream

Description

This is a counter-part of snd_pcm_stream_lock_irq().

void snd_pcm_stream_unlock_irqrestore(struct snd_pcm_substream *substream, unsigned long flags)¶: Unlock the PCM stream

Parameters

struct snd_pcm_substream *substream: PCM substream
unsigned long flags: irq flags

Description

This is a counter-part of snd_pcm_stream_lock_irqsave().

int snd_pcm_hw_params_choose(struct snd_pcm_substream *pcm, struct snd_pcm_hw_params *params)¶: choose a configuration defined by params

Parameters

struct snd_pcm_substream *pcm: PCM instance
struct snd_pcm_hw_params *params: the hw_params instance

Description

Choose one configuration from configuration space defined by params. The configuration chosen is that obtained fixing in this order: first access, first format, first subformat, min channels, min rate, min period time, max buffer size, min tick time

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_start(struct snd_pcm_substream *substream)¶: start all linked streams

Parameters

struct snd_pcm_substream *substream: the PCM substream instance

Return

Zero if successful, or a negative error code. The stream lock must be acquired before calling this function.

int snd_pcm_stop(struct snd_pcm_substream *substream, snd_pcm_state_t state)¶: try to stop all running streams in the substream group

Parameters

struct snd_pcm_substream *substream: the PCM substream instance
snd_pcm_state_t state: PCM state after stopping the stream

Description

The state of each stream is then changed to the given state unconditionally.

Return

Zero if successful, or a negative error code.

int snd_pcm_drain_done(struct snd_pcm_substream *substream)¶: stop the DMA only when the given stream is playback

Parameters

struct snd_pcm_substream *substream: the PCM substream

Description

After stopping, the state is changed to SETUP. Unlike snd_pcm_stop(), this affects only the given stream.

Return

Zero if successful, or a negative error code.

int snd_pcm_stop_xrun(struct snd_pcm_substream *substream)¶: stop the running streams as XRUN

Parameters

struct snd_pcm_substream *substream: the PCM substream instance

Description

This stops the given running substream (and all linked substreams) as XRUN. Unlike snd_pcm_stop(), this function takes the substream lock by itself.

Return

Zero if successful, or a negative error code.

int snd_pcm_suspend_all(struct snd_pcm *pcm)¶: trigger SUSPEND to all substreams in the given pcm

Parameters

struct snd_pcm *pcm: the PCM instance

Description

After this call, all streams are changed to SUSPENDED state.

Return

Zero if successful (or pcm is NULL), or a negative error code.

int snd_pcm_prepare(struct snd_pcm_substream *substream, struct file *file)¶: prepare the PCM substream to be triggerable

Parameters

struct snd_pcm_substream *substream: the PCM substream instance
struct file *file: file to refer f_flags

Return

Zero if successful, or a negative error code.

int snd_pcm_kernel_ioctl(struct snd_pcm_substream *substream, unsigned int cmd, void *arg)¶: Execute PCM ioctl in the kernel-space

Parameters

struct snd_pcm_substream *substream: PCM substream
unsigned int cmd: IOCTL cmd
void *arg: IOCTL argument

Description

The function is provided primarily for OSS layer and USB gadget drivers, and it allows only the limited set of ioctls (hw_params, sw_params, prepare, start, drain, drop, forward).

Return

zero if successful, or a negative error code

int snd_pcm_lib_default_mmap(struct snd_pcm_substream *substream, struct vm_area_struct *area)¶: Default PCM data mmap function

Parameters

struct snd_pcm_substream *substream: PCM substream
struct vm_area_struct *area: VMA

Description

This is the default mmap handler for PCM data. When mmap pcm_ops is NULL, this function is invoked implicitly.

Return

zero if successful, or a negative error code

int snd_pcm_lib_mmap_iomem(struct snd_pcm_substream *substream, struct vm_area_struct *area)¶: Default PCM data mmap function for I/O mem

Parameters

struct snd_pcm_substream *substream: PCM substream
struct vm_area_struct *area: VMA

Description

When your hardware uses the iomapped pages as the hardware buffer and wants to mmap it, pass this function as mmap pcm_ops. Note that this is supposed to work only on limited architectures.

Return

zero if successful, or a negative error code

int snd_pcm_stream_linked(struct snd_pcm_substream *substream)¶: Check whether the substream is linked with others

Parameters

struct snd_pcm_substream *substream: substream to check

Return

true if the given substream is being linked with others

snd_pcm_stream_lock_irqsave¶

snd_pcm_stream_lock_irqsave (substream, flags)

Lock the PCM stream

Parameters

substream: PCM substream
flags: irq flags

Description

This locks the PCM stream like snd_pcm_stream_lock() but with the local IRQ (only when nonatomic is false). In nonatomic case, this is identical as snd_pcm_stream_lock().

snd_pcm_stream_lock_irqsave_nested¶

snd_pcm_stream_lock_irqsave_nested (substream, flags)

Single-nested PCM stream locking

Parameters

substream: PCM substream
flags: irq flags

Description

This locks the PCM stream like snd_pcm_stream_lock_irqsave() but with the single-depth lockdep subclass.

snd_pcm_group_for_each_entry¶

snd_pcm_group_for_each_entry (s, substream)

iterate over the linked substreams

Parameters

s: the iterator
substream: the substream

Description

Iterate over the all linked substreams to the given substream. When substream isn’t linked with any others, this gives returns substream itself once.

int snd_pcm_running(struct snd_pcm_substream *substream)¶: Check whether the substream is in a running state

Parameters

struct snd_pcm_substream *substream: substream to check

Return

true if the given substream is in the state RUNNING, or in the state DRAINING for playback.

void __snd_pcm_set_state(struct snd_pcm_runtime *runtime, snd_pcm_state_t state)¶: Change the current PCM state

Parameters

struct snd_pcm_runtime *runtime: PCM runtime to set
snd_pcm_state_t state: the current state to set

Description

Call within the stream lock

ssize_t bytes_to_samples(struct snd_pcm_runtime *runtime, ssize_t size)¶: Unit conversion of the size from bytes to samples

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
ssize_t size: size in bytes

Return

the size in samples

snd_pcm_sframes_t bytes_to_frames(struct snd_pcm_runtime *runtime, ssize_t size)¶: Unit conversion of the size from bytes to frames

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
ssize_t size: size in bytes

Return

the size in frames

ssize_t samples_to_bytes(struct snd_pcm_runtime *runtime, ssize_t size)¶: Unit conversion of the size from samples to bytes

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
ssize_t size: size in samples

Return

the byte size

ssize_t frames_to_bytes(struct snd_pcm_runtime *runtime, snd_pcm_sframes_t size)¶: Unit conversion of the size from frames to bytes

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
snd_pcm_sframes_t size: size in frames

Return

the byte size

int frame_aligned(struct snd_pcm_runtime *runtime, ssize_t bytes)¶: Check whether the byte size is aligned to frames

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
ssize_t bytes: size in bytes

Return

true if aligned, or false if not

size_t snd_pcm_lib_buffer_bytes(struct snd_pcm_substream *substream)¶: Get the buffer size of the current PCM in bytes

Parameters

struct snd_pcm_substream *substream: PCM substream

Return

buffer byte size

size_t snd_pcm_lib_period_bytes(struct snd_pcm_substream *substream)¶: Get the period size of the current PCM in bytes

Parameters

struct snd_pcm_substream *substream: PCM substream

Return

period byte size

snd_pcm_uframes_t snd_pcm_playback_avail(struct snd_pcm_runtime *runtime)¶: Get the available (writable) space for playback

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance

Description

Result is between 0 ... (boundary - 1)

Return

available frame size

snd_pcm_uframes_t snd_pcm_capture_avail(struct snd_pcm_runtime *runtime)¶: Get the available (readable) space for capture

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance

Description

Result is between 0 ... (boundary - 1)

Return

available frame size

snd_pcm_sframes_t snd_pcm_playback_hw_avail(struct snd_pcm_runtime *runtime)¶: Get the queued space for playback

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance

Return

available frame size

snd_pcm_sframes_t snd_pcm_capture_hw_avail(struct snd_pcm_runtime *runtime)¶: Get the free space for capture

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance

Return

available frame size

int snd_pcm_playback_ready(struct snd_pcm_substream *substream)¶: check whether the playback buffer is available

Parameters

struct snd_pcm_substream *substream: the pcm substream instance

Description

Checks whether enough free space is available on the playback buffer.

Return

Non-zero if available, or zero if not.

int snd_pcm_capture_ready(struct snd_pcm_substream *substream)¶: check whether the capture buffer is available

Parameters

struct snd_pcm_substream *substream: the pcm substream instance

Description

Checks whether enough capture data is available on the capture buffer.

Return

Non-zero if available, or zero if not.

int snd_pcm_playback_data(struct snd_pcm_substream *substream)¶: check whether any data exists on the playback buffer

Parameters

struct snd_pcm_substream *substream: the pcm substream instance

Description

Checks whether any data exists on the playback buffer.

Return

Non-zero if any data exists, or zero if not. If stop_threshold is bigger or equal to boundary, then this function returns always non-zero.

int snd_pcm_playback_empty(struct snd_pcm_substream *substream)¶: check whether the playback buffer is empty

Parameters

struct snd_pcm_substream *substream: the pcm substream instance

Description

Checks whether the playback buffer is empty.

Return

Non-zero if empty, or zero if not.

int snd_pcm_capture_empty(struct snd_pcm_substream *substream)¶: check whether the capture buffer is empty

Parameters

struct snd_pcm_substream *substream: the pcm substream instance

Description

Checks whether the capture buffer is empty.

Return

Non-zero if empty, or zero if not.

void snd_pcm_trigger_done(struct snd_pcm_substream *substream, struct snd_pcm_substream *master)¶: Mark the master substream

Parameters

struct snd_pcm_substream *substream: the pcm substream instance
struct snd_pcm_substream *master: the linked master substream

Description

When multiple substreams of the same card are linked and the hardware supports the single-shot operation, the driver calls this in the loop in snd_pcm_group_for_each_entry() for marking the substream as “done”. Then most of trigger operations are performed only to the given master substream.

The trigger_master mark is cleared at timestamp updates at the end of trigger operations.

unsigned int params_channels(const struct snd_pcm_hw_params *p)¶: Get the number of channels from the hw params

Parameters

const struct snd_pcm_hw_params *p: hw params

Return

the number of channels

unsigned int params_rate(const struct snd_pcm_hw_params *p)¶: Get the sample rate from the hw params

Parameters

const struct snd_pcm_hw_params *p: hw params

Return

the sample rate

unsigned int params_period_size(const struct snd_pcm_hw_params *p)¶: Get the period size (in frames) from the hw params

Parameters

const struct snd_pcm_hw_params *p: hw params

Return

the period size in frames

unsigned int params_periods(const struct snd_pcm_hw_params *p)¶: Get the number of periods from the hw params

Parameters

const struct snd_pcm_hw_params *p: hw params

Return

the number of periods

unsigned int params_buffer_size(const struct snd_pcm_hw_params *p)¶: Get the buffer size (in frames) from the hw params

Parameters

const struct snd_pcm_hw_params *p: hw params

Return

the buffer size in frames

unsigned int params_buffer_bytes(const struct snd_pcm_hw_params *p)¶: Get the buffer size (in bytes) from the hw params

Parameters

const struct snd_pcm_hw_params *p: hw params

Return

the buffer size in bytes

int snd_pcm_hw_constraint_single(struct snd_pcm_runtime *runtime, snd_pcm_hw_param_t var, unsigned int val)¶: Constrain parameter to a single value

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
snd_pcm_hw_param_t var: The hw_params variable to constrain
unsigned int val: The value to constrain to

Return

Positive if the value is changed, zero if it’s not changed, or a negative error code.

int snd_pcm_format_cpu_endian(snd_pcm_format_t format)¶: Check the PCM format is CPU-endian

Parameters

snd_pcm_format_t format: the format to check

Return

1 if the given PCM format is CPU-endian, 0 if opposite, or a negative error code if endian not specified.

void snd_pcm_set_sync(struct snd_pcm_substream *substream)¶: set the PCM sync id

Parameters

struct snd_pcm_substream *substream: the pcm substream

Description

Use the default PCM sync identifier for the specific card.

void snd_pcm_set_runtime_buffer(struct snd_pcm_substream *substream, struct snd_dma_buffer *bufp)¶: Set the PCM runtime buffer

Parameters

struct snd_pcm_substream *substream: PCM substream to set
struct snd_dma_buffer *bufp: the buffer information, NULL to clear

Description

Copy the buffer information to runtime->dma_buffer when bufp is non-NULL. Otherwise it clears the current buffer information.

void snd_pcm_gettime(struct snd_pcm_runtime *runtime, struct timespec64 *tv)¶: Fill the timespec64 depending on the timestamp mode

Parameters

struct snd_pcm_runtime *runtime: PCM runtime instance
struct timespec64 *tv: timespec64 to fill

int snd_pcm_set_fixed_buffer(struct snd_pcm_substream *substream, int type, struct device *data, size_t size)¶: Preallocate and set up the fixed size PCM buffer

Parameters

struct snd_pcm_substream *substream: the pcm substream instance
int type: DMA type (SNDRV_DMA_TYPE_*)
struct device *data: DMA type dependent data
size_t size: the requested pre-allocation size in bytes

Description

This is a variant of snd_pcm_set_managed_buffer(), but this pre-allocates only the given sized buffer and doesn’t allow re-allocation nor dynamic allocation of a larger buffer unlike the standard one. The function may return -ENOMEM error, hence the caller must check it.

Return

zero if successful, or a negative error code

int snd_pcm_set_fixed_buffer_all(struct snd_pcm *pcm, int type, struct device *data, size_t size)¶: Preallocate and set up the fixed size PCM buffer

Parameters

struct snd_pcm *pcm: the pcm instance
int type: DMA type (SNDRV_DMA_TYPE_*)
struct device *data: DMA type dependent data
size_t size: the requested pre-allocation size in bytes

Description

Apply the set up of the fixed buffer via snd_pcm_set_fixed_buffer() for all substream. If any of allocation fails, it returns -ENOMEM, hence the caller must check the return value.

Return

zero if successful, or a negative error code

int snd_pcm_lib_alloc_vmalloc_buffer(struct snd_pcm_substream *substream, size_t size)¶: allocate virtual DMA buffer

Parameters

struct snd_pcm_substream *substream: the substream to allocate the buffer to
size_t size: the requested buffer size, in bytes

Description

Allocates the PCM substream buffer using vmalloc(), i.e., the memory is contiguous in kernel virtual space, but not in physical memory. Use this if the buffer is accessed by kernel code but not by device DMA.

Return

1 if the buffer was changed, 0 if not changed, or a negative error code.

int snd_pcm_lib_alloc_vmalloc_32_buffer(struct snd_pcm_substream *substream, size_t size)¶: allocate 32-bit-addressable buffer

Parameters

struct snd_pcm_substream *substream: the substream to allocate the buffer to
size_t size: the requested buffer size, in bytes

Description

This function works like snd_pcm_lib_alloc_vmalloc_buffer(), but uses vmalloc_32(), i.e., the pages are allocated from 32-bit-addressable memory.

Return

1 if the buffer was changed, 0 if not changed, or a negative error code.

dma_addr_t snd_pcm_sgbuf_get_addr(struct snd_pcm_substream *substream, unsigned int ofs)¶: Get the DMA address at the corresponding offset

Parameters

struct snd_pcm_substream *substream: PCM substream
unsigned int ofs: byte offset

Return

DMA address

unsigned int snd_pcm_sgbuf_get_chunk_size(struct snd_pcm_substream *substream, unsigned int ofs, unsigned int size)¶: Compute the max size that fits within the contig. page from the given size

Parameters

struct snd_pcm_substream *substream: PCM substream
unsigned int ofs: byte offset
unsigned int size: byte size to examine

Return

chunk size

void snd_pcm_mmap_data_open(struct vm_area_struct *area)¶: increase the mmap counter

Parameters

struct vm_area_struct *area: VMA

Description

PCM mmap callback should handle this counter properly

void snd_pcm_mmap_data_close(struct vm_area_struct *area)¶: decrease the mmap counter

Parameters

struct vm_area_struct *area: VMA

Description

PCM mmap callback should handle this counter properly

void snd_pcm_limit_isa_dma_size(int dma, size_t *max)¶: Get the max size fitting with ISA DMA transfer

Parameters

int dma: DMA number
size_t *max: pointer to store the max size

const char *snd_pcm_direction_name(int direction)¶: Get a string naming the direction of a stream

Parameters

int direction: Stream’s direction, one of SNDRV_PCM_STREAM_XXX

Description

Returns a string naming the direction of the stream.

const char *snd_pcm_stream_str(struct snd_pcm_substream *substream)¶: Get a string naming the direction of a stream

Parameters

struct snd_pcm_substream *substream: the pcm substream instance

Return

A string naming the direction of the stream.

struct snd_pcm_substream *snd_pcm_chmap_substream(struct snd_pcm_chmap *info, unsigned int idx)¶: get the PCM substream assigned to the given chmap info

Parameters

struct snd_pcm_chmap *info: chmap information
unsigned int idx: the substream number index

Return

the matched PCM substream, or NULL if not found

u64 pcm_format_to_bits(snd_pcm_format_t pcm_format)¶: Strong-typed conversion of pcm_format to bitwise

Parameters

snd_pcm_format_t pcm_format: PCM format

Return

64bit mask corresponding to the given PCM format

pcm_for_each_format¶

pcm_for_each_format (f)

helper to iterate for each format type

Parameters

f: the iterator variable in snd_pcm_format_t type

PCM Format Helpers¶

int snd_pcm_format_signed(snd_pcm_format_t format)¶: Check the PCM format is signed linear

Parameters

snd_pcm_format_t format: the format to check

Return

1 if the given PCM format is signed linear, 0 if unsigned linear, and a negative error code for non-linear formats.

int snd_pcm_format_unsigned(snd_pcm_format_t format)¶: Check the PCM format is unsigned linear

Parameters

snd_pcm_format_t format: the format to check

Return

1 if the given PCM format is unsigned linear, 0 if signed linear, and a negative error code for non-linear formats.

int snd_pcm_format_linear(snd_pcm_format_t format)¶: Check the PCM format is linear

Parameters

snd_pcm_format_t format: the format to check

Return

1 if the given PCM format is linear, 0 if not.

int snd_pcm_format_little_endian(snd_pcm_format_t format)¶: Check the PCM format is little-endian

Parameters

snd_pcm_format_t format: the format to check

Return

1 if the given PCM format is little-endian, 0 if big-endian, or a negative error code if endian not specified.

int snd_pcm_format_big_endian(snd_pcm_format_t format)¶: Check the PCM format is big-endian

Parameters

snd_pcm_format_t format: the format to check

Return

1 if the given PCM format is big-endian, 0 if little-endian, or a negative error code if endian not specified.

int snd_pcm_format_width(snd_pcm_format_t format)¶: return the bit-width of the format

Parameters

snd_pcm_format_t format: the format to check

Return

The bit-width of the format, or a negative error code if unknown format.

int snd_pcm_format_physical_width(snd_pcm_format_t format)¶: return the physical bit-width of the format

Parameters

snd_pcm_format_t format: the format to check

Return

The physical bit-width of the format, or a negative error code if unknown format.

ssize_t snd_pcm_format_size(snd_pcm_format_t format, size_t samples)¶: return the byte size of samples on the given format

Parameters

snd_pcm_format_t format: the format to check
size_t samples: sampling rate

Return

The byte size of the given samples for the format, or a negative error code if unknown format.

const unsigned char *snd_pcm_format_silence_64(snd_pcm_format_t format)¶: return the silent data in 8 bytes array

Parameters

snd_pcm_format_t format: the format to check

Return

The format pattern to fill or NULL if error.

int snd_pcm_format_set_silence(snd_pcm_format_t format, void *data, unsigned int samples)¶: set the silence data on the buffer

Parameters

snd_pcm_format_t format: the PCM format
void *data: the buffer pointer
unsigned int samples: the number of samples to set silence

Description

Sets the silence data on the buffer for the given samples.

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_hw_limit_rates(struct snd_pcm_hardware *hw)¶: determine rate_min/rate_max fields

Parameters

struct snd_pcm_hardware *hw: the pcm hw instance

Description

Determines the rate_min and rate_max fields from the rates bits of the given hw.

Return

Zero if successful.

unsigned int snd_pcm_rate_to_rate_bit(unsigned int rate)¶: converts sample rate to SNDRV_PCM_RATE_xxx bit

Parameters

unsigned int rate: the sample rate to convert

Return

The SNDRV_PCM_RATE_xxx flag that corresponds to the given rate, or SNDRV_PCM_RATE_KNOT for an unknown rate.

unsigned int snd_pcm_rate_bit_to_rate(unsigned int rate_bit)¶: converts SNDRV_PCM_RATE_xxx bit to sample rate

Parameters

unsigned int rate_bit: the rate bit to convert

Return

The sample rate that corresponds to the given SNDRV_PCM_RATE_xxx flag or 0 for an unknown rate bit.

unsigned int snd_pcm_rate_mask_intersect(unsigned int rates_a, unsigned int rates_b)¶: computes the intersection between two rate masks

Parameters

unsigned int rates_a: The first rate mask
unsigned int rates_b: The second rate mask

Description

This function computes the rates that are supported by both rate masks passed to the function. It will take care of the special handling of SNDRV_PCM_RATE_CONTINUOUS and SNDRV_PCM_RATE_KNOT.

Return

A rate mask containing the rates that are supported by both rates_a and rates_b.

unsigned int snd_pcm_rate_range_to_bits(unsigned int rate_min, unsigned int rate_max)¶: converts rate range to SNDRV_PCM_RATE_xxx bit

Parameters

unsigned int rate_min: the minimum sample rate
unsigned int rate_max: the maximum sample rate

Description

This function has an implicit assumption: the rates in the given range have only the pre-defined rates like 44100 or 16000.

Return

The SNDRV_PCM_RATE_xxx flag that corresponds to the given rate range, or SNDRV_PCM_RATE_KNOT for an unknown range.

PCM Memory Management¶

void snd_pcm_lib_preallocate_free(struct snd_pcm_substream *substream)¶: release the preallocated buffer of the specified substream.

Parameters

struct snd_pcm_substream *substream: the pcm substream instance

Description

Releases the pre-allocated buffer of the given substream.

void snd_pcm_lib_preallocate_free_for_all(struct snd_pcm *pcm)¶: release all pre-allocated buffers on the pcm

Parameters

struct snd_pcm *pcm: the pcm instance

Description

Releases all the pre-allocated buffers on the given pcm.

void snd_pcm_lib_preallocate_pages(struct snd_pcm_substream *substream, int type, struct device *data, size_t size, size_t max)¶: pre-allocation for the given DMA type

Parameters

struct snd_pcm_substream *substream: the pcm substream instance
int type: DMA type (SNDRV_DMA_TYPE_*)
struct device *data: DMA type dependent data
size_t size: the requested pre-allocation size in bytes
size_t max: the max. allowed pre-allocation size

Description

Do pre-allocation for the given DMA buffer type.

void snd_pcm_lib_preallocate_pages_for_all(struct snd_pcm *pcm, int type, void *data, size_t size, size_t max)¶: pre-allocation for continuous memory type (all substreams)

Parameters

struct snd_pcm *pcm: the pcm instance
int type: DMA type (SNDRV_DMA_TYPE_*)
void *data: DMA type dependent data
size_t size: the requested pre-allocation size in bytes
size_t max: the max. allowed pre-allocation size

Description

Do pre-allocation to all substreams of the given pcm for the specified DMA type.

int snd_pcm_set_managed_buffer(struct snd_pcm_substream *substream, int type, struct device *data, size_t size, size_t max)¶: set up buffer management for a substream

Parameters

struct snd_pcm_substream *substream: the pcm substream instance
int type: DMA type (SNDRV_DMA_TYPE_*)
struct device *data: DMA type dependent data
size_t size: the requested pre-allocation size in bytes
size_t max: the max. allowed pre-allocation size

Description

Do pre-allocation for the given DMA buffer type, and set the managed buffer allocation mode to the given substream. In this mode, PCM core will allocate a buffer automatically before PCM hw_params ops call, and release the buffer after PCM hw_free ops call as well, so that the driver doesn’t need to invoke the allocation and the release explicitly in its callback. When a buffer is actually allocated before the PCM hw_params call, it turns on the runtime buffer_changed flag for drivers changing their h/w parameters accordingly.

When size is non-zero and max is zero, this tries to allocate for only the exact buffer size without fallback, and may return -ENOMEM. Otherwise, the function tries to allocate smaller chunks if the allocation fails. This is the behavior of snd_pcm_set_fixed_buffer().

When both size and max are zero, the function only sets up the buffer for later dynamic allocations. It’s used typically for buffers with SNDRV_DMA_TYPE_VMALLOC type.

Upon successful buffer allocation and setup, the function returns 0.

Return

zero if successful, or a negative error code

int snd_pcm_set_managed_buffer_all(struct snd_pcm *pcm, int type, struct device *data, size_t size, size_t max)¶: set up buffer management for all substreams for all substreams

Parameters

struct snd_pcm *pcm: the pcm instance
int type: DMA type (SNDRV_DMA_TYPE_*)
struct device *data: DMA type dependent data
size_t size: the requested pre-allocation size in bytes
size_t max: the max. allowed pre-allocation size

Description

Do pre-allocation to all substreams of the given pcm for the specified DMA type and size, and set the managed_buffer_alloc flag to each substream.

Return

zero if successful, or a negative error code

int snd_pcm_lib_malloc_pages(struct snd_pcm_substream *substream, size_t size)¶: allocate the DMA buffer

Parameters

struct snd_pcm_substream *substream: the substream to allocate the DMA buffer to
size_t size: the requested buffer size in bytes

Description

Allocates the DMA buffer on the BUS type given earlier to snd_pcm_lib_preallocate_xxx_pages().

Return

1 if the buffer is changed, 0 if not changed, or a negative code on failure.

int snd_pcm_lib_free_pages(struct snd_pcm_substream *substream)¶: release the allocated DMA buffer.

Parameters

struct snd_pcm_substream *substream: the substream to release the DMA buffer

Description

Releases the DMA buffer allocated via snd_pcm_lib_malloc_pages().

Return

Zero if successful, or a negative error code on failure.

int snd_pcm_lib_free_vmalloc_buffer(struct snd_pcm_substream *substream)¶: free vmalloc buffer

Parameters

struct snd_pcm_substream *substream: the substream with a buffer allocated by snd_pcm_lib_alloc_vmalloc_buffer()

Return

Zero if successful, or a negative error code on failure.

struct page *snd_pcm_lib_get_vmalloc_page(struct snd_pcm_substream *substream, unsigned long offset)¶: map vmalloc buffer offset to page struct

Parameters

struct snd_pcm_substream *substream: the substream with a buffer allocated by snd_pcm_lib_alloc_vmalloc_buffer()
unsigned long offset: offset in the buffer

Description

This function is to be used as the page callback in the PCM ops.

Return

The page struct, or NULL on failure.

PCM DMA Engine API¶

int snd_hwparams_to_dma_slave_config(const struct snd_pcm_substream *substream, const struct snd_pcm_hw_params *params, struct dma_slave_config *slave_config)¶: Convert hw_params to dma_slave_config

Parameters

const struct snd_pcm_substream *substream: PCM substream
const struct snd_pcm_hw_params *params: hw_params
struct dma_slave_config *slave_config: DMA slave config

Description

This function can be used to initialize a dma_slave_config from a substream and hw_params in a dmaengine based PCM driver implementation.

Return

zero if successful, or a negative error code

void snd_dmaengine_pcm_set_config_from_dai_data(const struct snd_pcm_substream *substream, const struct snd_dmaengine_dai_dma_data *dma_data, struct dma_slave_config *slave_config)¶: Initializes a dma slave config using DAI DMA data.

Parameters

const struct snd_pcm_substream *substream: PCM substream
const struct snd_dmaengine_dai_dma_data *dma_data: DAI DMA data
struct dma_slave_config *slave_config: DMA slave configuration

Description

Initializes the {dst,src}_addr, {dst,src}_maxburst, {dst,src}_addr_width fields of the DMA slave config from the same fields of the DAI DMA data struct. The src and dst fields will be initialized depending on the direction of the substream. If the substream is a playback stream the dst fields will be initialized, if it is a capture stream the src fields will be initialized. The {dst,src}_addr_width field will only be initialized if the SND_DMAENGINE_PCM_DAI_FLAG_PACK flag is set or if the addr_width field of the DAI DMA data struct is not equal to DMA_SLAVE_BUSWIDTH_UNDEFINED. If both conditions are met the latter takes priority.

int snd_dmaengine_pcm_trigger(struct snd_pcm_substream *substream, int cmd)¶: dmaengine based PCM trigger implementation

Parameters

struct snd_pcm_substream *substream: PCM substream
int cmd: Trigger command

Description

This function can be used as the PCM trigger callback for dmaengine based PCM driver implementations.

Return

0 on success, a negative error code otherwise

snd_pcm_uframes_t snd_dmaengine_pcm_pointer_no_residue(struct snd_pcm_substream *substream)¶: dmaengine based PCM pointer implementation

Parameters

struct snd_pcm_substream *substream: PCM substream

Description

This function is deprecated and should not be used by new drivers, as its results may be unreliable.

Return

PCM position in frames

snd_pcm_uframes_t snd_dmaengine_pcm_pointer(struct snd_pcm_substream *substream)¶: dmaengine based PCM pointer implementation

Parameters

struct snd_pcm_substream *substream: PCM substream

Description

This function can be used as the PCM pointer callback for dmaengine based PCM driver implementations.

Return

PCM position in frames

struct dma_chan *snd_dmaengine_pcm_request_channel(dma_filter_fn filter_fn, void *filter_data)¶: Request channel for the dmaengine PCM

Parameters

dma_filter_fn filter_fn: Filter function used to request the DMA channel
void *filter_data: Data passed to the DMA filter function

Description

This function request a DMA channel for usage with dmaengine PCM.

Return

NULL or the requested DMA channel

int snd_dmaengine_pcm_open(struct snd_pcm_substream *substream, struct dma_chan *chan)¶: Open a dmaengine based PCM substream

Parameters

struct snd_pcm_substream *substream: PCM substream
struct dma_chan *chan: DMA channel to use for data transfers

Description

The function should usually be called from the pcm open callback. Note that this function will use private_data field of the substream’s runtime. So it is not available to your pcm driver implementation.

Return

0 on success, a negative error code otherwise

int snd_dmaengine_pcm_open_request_chan(struct snd_pcm_substream *substream, dma_filter_fn filter_fn, void *filter_data)¶: Open a dmaengine based PCM substream and request channel

Parameters

struct snd_pcm_substream *substream: PCM substream
dma_filter_fn filter_fn: Filter function used to request the DMA channel
void *filter_data: Data passed to the DMA filter function

Description

This function will request a DMA channel using the passed filter function and data. The function should usually be called from the pcm open callback. Note that this function will use private_data field of the substream’s runtime. So it is not available to your pcm driver implementation.

Return

0 on success, a negative error code otherwise

int snd_dmaengine_pcm_close(struct snd_pcm_substream *substream)¶: Close a dmaengine based PCM substream

Parameters

struct snd_pcm_substream *substream: PCM substream

Return

0 on success, a negative error code otherwise

int snd_dmaengine_pcm_close_release_chan(struct snd_pcm_substream *substream)¶: Close a dmaengine based PCM substream and release channel

Parameters

struct snd_pcm_substream *substream: PCM substream

Description

Releases the DMA channel associated with the PCM substream.

Return

zero if successful, or a negative error code

int snd_dmaengine_pcm_refine_runtime_hwparams(struct snd_pcm_substream *substream, struct snd_dmaengine_dai_dma_data *dma_data, struct snd_pcm_hardware *hw, struct dma_chan *chan)¶: Refine runtime hw params

Parameters

struct snd_pcm_substream *substream: PCM substream
struct snd_dmaengine_dai_dma_data *dma_data: DAI DMA data
struct snd_pcm_hardware *hw: PCM hw params
struct dma_chan *chan: DMA channel to use for data transfers

Description

This function will query DMA capability, then refine the pcm hardware parameters.

Return

0 on success, a negative error code otherwise

enum dma_transfer_direction snd_pcm_substream_to_dma_direction(const struct snd_pcm_substream *substream)¶: Get dma_transfer_direction for a PCM substream

Parameters

const struct snd_pcm_substream *substream: PCM substream

Return

DMA transfer direction

struct snd_dmaengine_dai_dma_data¶: DAI DMA configuration data

Definition:

struct snd_dmaengine_dai_dma_data {
    dma_addr_t addr;
    enum dma_slave_buswidth addr_width;
    u32 maxburst;
    void *filter_data;
    const char *chan_name;
    unsigned int fifo_size;
    unsigned int flags;
    void *peripheral_config;
    size_t peripheral_size;
};

Members

addr: Address of the DAI data source or destination register.
addr_width: Width of the DAI data source or destination register.
maxburst: Maximum number of words(note: words, as in units of the src_addr_width member, not bytes) that can be send to or received from the DAI in one burst.
filter_data: Custom DMA channel filter data, this will usually be used when requesting the DMA channel.
chan_name: Custom channel name to use when requesting DMA channel.
fifo_size: FIFO size of the DAI controller in bytes
flags: PCM_DAI flags, only SND_DMAENGINE_PCM_DAI_FLAG_PACK for now
peripheral_config: peripheral configuration for programming peripheral for dmaengine transfer
peripheral_size: peripheral configuration buffer size

struct snd_dmaengine_pcm_config¶: Configuration data for dmaengine based PCM

Definition:

struct snd_dmaengine_pcm_config {
    int (*prepare_slave_config)(struct snd_pcm_substream *substream,struct snd_pcm_hw_params *params, struct dma_slave_config *slave_config);
    struct dma_chan *(*compat_request_channel)(struct snd_soc_pcm_runtime *rtd, struct snd_pcm_substream *substream);
    int (*process)(struct snd_pcm_substream *substream,int channel, unsigned long hwoff, unsigned long bytes);
    const char *name;
    dma_filter_fn compat_filter_fn;
    struct device *dma_dev;
    const char *chan_names[SNDRV_PCM_STREAM_LAST + 1];
    const struct snd_pcm_hardware *pcm_hardware;
    unsigned int prealloc_buffer_size;
};

Members

prepare_slave_config: Callback used to fill in the DMA slave_config for a PCM substream. Will be called from the PCM drivers hwparams callback.
compat_request_channel: Callback to request a DMA channel for platforms which do not use devicetree.
process: Callback used to apply processing on samples transferred from/to user space.
name: Component name. If null, dev_name will be used.
compat_filter_fn: Will be used as the filter function when requesting a channel for platforms which do not use devicetree. The filter parameter will be the DAI’s DMA data.
dma_dev: If set, request DMA channel on this device rather than the DAI device.
chan_names: If set, these custom DMA channel names will be requested at registration time.
pcm_hardware: snd_pcm_hardware struct to be used for the PCM.
prealloc_buffer_size: Size of the preallocated audio buffer.

Note

If both compat_request_channel and compat_filter_fn are set compat_request_channel will be used to request the channel and compat_filter_fn will be ignored. Otherwise the channel will be requested using dma_request_channel with compat_filter_fn as the filter function.

Control/Mixer API¶

General Control Interface¶

void snd_ctl_notify(struct snd_card *card, unsigned int mask, struct snd_ctl_elem_id *id)¶: Send notification to user-space for a control change

Parameters

struct snd_card *card: the card to send notification
unsigned int mask: the event mask, SNDRV_CTL_EVENT_*
struct snd_ctl_elem_id *id: the ctl element id to send notification

Description

This function adds an event record with the given id and mask, appends to the list and wakes up the user-space for notification. This can be called in the atomic context.

void snd_ctl_notify_one(struct snd_card *card, unsigned int mask, struct snd_kcontrol *kctl, unsigned int ioff)¶: Send notification to user-space for a control change

Parameters

struct snd_card *card: the card to send notification
unsigned int mask: the event mask, SNDRV_CTL_EVENT_*
struct snd_kcontrol *kctl: the pointer with the control instance
unsigned int ioff: the additional offset to the control index

Description

This function calls snd_ctl_notify() and does additional jobs like LED state changes.

int snd_ctl_new(struct snd_kcontrol **kctl, unsigned int count, unsigned int access, struct snd_ctl_file *file)¶: create a new control instance with some elements

Parameters

struct snd_kcontrol **kctl: the pointer to store new control instance
unsigned int count: the number of elements in this control
unsigned int access: the default access flags for elements in this control
struct snd_ctl_file *file: given when locking these elements

Description

Allocates a memory object for a new control instance. The instance has elements as many as the given number (count). Each element has given access permissions (access). Each element is locked when file is given.

Return

0 on success, error code on failure

struct snd_kcontrol *snd_ctl_new1(const struct snd_kcontrol_new *ncontrol, void *private_data)¶: create a control instance from the template

Parameters

const struct snd_kcontrol_new *ncontrol: the initialization record
void *private_data: the private data to set

Description

Allocates a new struct snd_kcontrol instance and initialize from the given template. When the access field of ncontrol is 0, it’s assumed as READWRITE access. When the count field is 0, it’s assumes as one.

Return

The pointer of the newly generated instance, or NULL on failure.

void snd_ctl_free_one(struct snd_kcontrol *kcontrol)¶: release the control instance

Parameters

struct snd_kcontrol *kcontrol: the control instance

Description

Releases the control instance created via snd_ctl_new() or snd_ctl_new1(). Don’t call this after the control was added to the card.

int snd_ctl_add(struct snd_card *card, struct snd_kcontrol *kcontrol)¶: add the control instance to the card

Parameters

struct snd_card *card: the card instance
struct snd_kcontrol *kcontrol: the control instance to add

Description

Adds the control instance created via snd_ctl_new() or snd_ctl_new1() to the given card. Assigns also an unique numid used for fast search.

It frees automatically the control which cannot be added.

Return

Zero if successful, or a negative error code on failure.

int snd_ctl_replace(struct snd_card *card, struct snd_kcontrol *kcontrol, bool add_on_replace)¶: replace the control instance of the card

Parameters

struct snd_card *card: the card instance
struct snd_kcontrol *kcontrol: the control instance to replace
bool add_on_replace: add the control if not already added

Description

Replaces the given control. If the given control does not exist and the add_on_replace flag is set, the control is added. If the control exists, it is destroyed first.

It frees automatically the control which cannot be added or replaced.

Return

Zero if successful, or a negative error code on failure.

int snd_ctl_remove(struct snd_card *card, struct snd_kcontrol *kcontrol)¶: remove the control from the card and release it

Parameters

struct snd_card *card: the card instance
struct snd_kcontrol *kcontrol: the control instance to remove

Description

Removes the control from the card and then releases the instance. You don’t need to call snd_ctl_free_one(). Passing NULL to kcontrol argument is allowed as noop.

Note that this function takes card->controls_rwsem lock internally.

Return

0 if successful, or a negative error code on failure.

int snd_ctl_remove_id(struct snd_card *card, struct snd_ctl_elem_id *id)¶: remove the control of the given id and release it

Parameters

struct snd_card *card: the card instance
struct snd_ctl_elem_id *id: the control id to remove

Description

Finds the control instance with the given id, removes it from the card list and releases it.

Return

0 if successful, or a negative error code on failure.

int snd_ctl_remove_user_ctl(struct snd_ctl_file *file, struct snd_ctl_elem_id *id)¶: remove and release the unlocked user control

Parameters

struct snd_ctl_file * file: active control handle
struct snd_ctl_elem_id *id: the control id to remove

Description

Finds the control instance with the given id, removes it from the card list and releases it.

Return

0 if successful, or a negative error code on failure.

int snd_ctl_activate_id(struct snd_card *card, struct snd_ctl_elem_id *id, int active)¶: activate/inactivate the control of the given id

Parameters

struct snd_card *card: the card instance
struct snd_ctl_elem_id *id: the control id to activate/inactivate
int active: non-zero to activate

Description

Finds the control instance with the given id, and activate or inactivate the control together with notification, if changed. The given ID data is filled with full information.

Return

0 if unchanged, 1 if changed, or a negative error code on failure.

int snd_ctl_rename_id(struct snd_card *card, struct snd_ctl_elem_id *src_id, struct snd_ctl_elem_id *dst_id)¶: replace the id of a control on the card

Parameters

struct snd_card *card: the card instance
struct snd_ctl_elem_id *src_id: the old id
struct snd_ctl_elem_id *dst_id: the new id

Description

Finds the control with the old id from the card, and replaces the id with the new one.

The function tries to keep the already assigned numid while replacing the rest.

Note that this function should be used only in the card initialization phase. Calling after the card instantiation may cause issues with user-space expecting persistent numids.

Return

Zero if successful, or a negative error code on failure.

void snd_ctl_rename(struct snd_card *card, struct snd_kcontrol *kctl, const char *name)¶: rename the control on the card

Parameters

struct snd_card *card: the card instance
struct snd_kcontrol *kctl: the control to rename
const char *name: the new name

Description

Renames the specified control on the card to the new name.

Note that this function takes card->controls_rwsem lock internally.

struct snd_kcontrol *snd_ctl_find_numid_locked(struct snd_card *card, unsigned int numid)¶: find the control instance with the given number-id

Parameters

struct snd_card *card: the card instance
unsigned int numid: the number-id to search

Description

Finds the control instance with the given number-id from the card.

The caller must down card->controls_rwsem before calling this function (if the race condition can happen).

Return

The pointer of the instance if found, or NULL if not.

struct snd_kcontrol *snd_ctl_find_numid(struct snd_card *card, unsigned int numid)¶: find the control instance with the given number-id

Parameters

struct snd_card *card: the card instance
unsigned int numid: the number-id to search

Description

Finds the control instance with the given number-id from the card.

Note that this function takes card->controls_rwsem lock internally.

Return

The pointer of the instance if found, or NULL if not.

struct snd_kcontrol *snd_ctl_find_id_locked(struct snd_card *card, const struct snd_ctl_elem_id *id)¶: find the control instance with the given id

Parameters

struct snd_card *card: the card instance
const struct snd_ctl_elem_id *id: the id to search

Description

Finds the control instance with the given id from the card.

The caller must down card->controls_rwsem before calling this function (if the race condition can happen).

Return

The pointer of the instance if found, or NULL if not.

struct snd_kcontrol *snd_ctl_find_id(struct snd_card *card, const struct snd_ctl_elem_id *id)¶: find the control instance with the given id

Parameters

struct snd_card *card: the card instance
const struct snd_ctl_elem_id *id: the id to search

Description

Finds the control instance with the given id from the card.

Note that this function takes card->controls_rwsem lock internally.

Return

The pointer of the instance if found, or NULL if not.

int snd_ctl_register_ioctl(snd_kctl_ioctl_func_t fcn)¶: register the device-specific control-ioctls

Parameters

snd_kctl_ioctl_func_t fcn: ioctl callback function

Description

called from each device manager like pcm.c, hwdep.c, etc.

Return

zero if successful, or a negative error code

int snd_ctl_register_ioctl_compat(snd_kctl_ioctl_func_t fcn)¶: register the device-specific 32bit compat control-ioctls

Parameters

snd_kctl_ioctl_func_t fcn: ioctl callback function

Return

zero if successful, or a negative error code

int snd_ctl_unregister_ioctl(snd_kctl_ioctl_func_t fcn)¶: de-register the device-specific control-ioctls

Parameters

snd_kctl_ioctl_func_t fcn: ioctl callback function to unregister

Return

zero if successful, or a negative error code

int snd_ctl_unregister_ioctl_compat(snd_kctl_ioctl_func_t fcn)¶: de-register the device-specific compat 32bit control-ioctls

Parameters

snd_kctl_ioctl_func_t fcn: ioctl callback function to unregister

Return

zero if successful, or a negative error code

int snd_ctl_request_layer(const char *module_name)¶: request to use the layer

Parameters

const char *module_name: Name of the kernel module (NULL == build-in)

Return

zero if successful, or an error code when the module cannot be loaded

void snd_ctl_register_layer(struct snd_ctl_layer_ops *lops)¶: register new control layer

Parameters

struct snd_ctl_layer_ops *lops: operation structure

Description

The new layer can track all control elements and do additional operations on top (like audio LED handling).

void snd_ctl_disconnect_layer(struct snd_ctl_layer_ops *lops)¶: disconnect control layer

Parameters

struct snd_ctl_layer_ops *lops: operation structure

Description

It is expected that the information about tracked cards is freed before this call (the disconnect callback is not called here).

int snd_ctl_boolean_mono_info(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_info *uinfo)¶: Helper function for a standard boolean info callback with a mono channel

Parameters

struct snd_kcontrol *kcontrol: the kcontrol instance
struct snd_ctl_elem_info *uinfo: info to store

Description

This is a function that can be used as info callback for a standard boolean control with a single mono channel.

Return

Zero (always successful)

int snd_ctl_boolean_stereo_info(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_info *uinfo)¶: Helper function for a standard boolean info callback with stereo two channels

Parameters

struct snd_kcontrol *kcontrol: the kcontrol instance
struct snd_ctl_elem_info *uinfo: info to store

Description

This is a function that can be used as info callback for a standard boolean control with stereo two channels.

Return

Zero (always successful)

int snd_ctl_enum_info(struct snd_ctl_elem_info *info, unsigned int channels, unsigned int items, const char *const names[])¶: fills the info structure for an enumerated control

Parameters

struct snd_ctl_elem_info *info: the structure to be filled
unsigned int channels: the number of the control’s channels; often one
unsigned int items: the number of control values; also the size of names
const char *const names[]: an array containing the names of all control values

Description

Sets all required fields in info to their appropriate values. If the control’s accessibility is not the default (readable and writable), the caller has to fill info->access.

Return

Zero (always successful)

AC97 Codec API¶

void snd_ac97_write(struct snd_ac97 *ac97, unsigned short reg, unsigned short value)¶: write a value on the given register

Parameters

struct snd_ac97 *ac97: the ac97 instance
unsigned short reg: the register to change
unsigned short value: the value to set

Description

Writes a value on the given register. This will invoke the write callback directly after the register check. This function doesn’t change the register cache unlike #snd_ca97_write_cache(), so use this only when you don’t want to reflect the change to the suspend/resume state.

unsigned short snd_ac97_read(struct snd_ac97 *ac97, unsigned short reg)¶: read a value from the given register

Parameters

struct snd_ac97 *ac97: the ac97 instance
unsigned short reg: the register to read

Description

Reads a value from the given register. This will invoke the read callback directly after the register check.

Return

The read value.

void snd_ac97_write_cache(struct snd_ac97 *ac97, unsigned short reg, unsigned short value)¶: write a value on the given register and update the cache

Parameters

struct snd_ac97 *ac97: the ac97 instance
unsigned short reg: the register to change
unsigned short value: the value to set

Description

Writes a value on the given register and updates the register cache. The cached values are used for the cached-read and the suspend/resume.

int snd_ac97_update(struct snd_ac97 *ac97, unsigned short reg, unsigned short value)¶: update the value on the given register

Parameters

struct snd_ac97 *ac97: the ac97 instance
unsigned short reg: the register to change
unsigned short value: the value to set

Description

Compares the value with the register cache and updates the value only when the value is changed.

Return

1 if the value is changed, 0 if no change, or a negative code on failure.

int snd_ac97_update_bits(struct snd_ac97 *ac97, unsigned short reg, unsigned short mask, unsigned short value)¶: update the bits on the given register

Parameters

struct snd_ac97 *ac97: the ac97 instance
unsigned short reg: the register to change
unsigned short mask: the bit-mask to change
unsigned short value: the value to set

Description

Updates the masked-bits on the given register only when the value is changed.

Return

1 if the bits are changed, 0 if no change, or a negative code on failure.

const char *snd_ac97_get_short_name(struct snd_ac97 *ac97)¶: retrieve codec name

Parameters

struct snd_ac97 *ac97: the codec instance

Return

The short identifying name of the codec.

int snd_ac97_bus(struct snd_card *card, int num, const struct snd_ac97_bus_ops *ops, void *private_data, struct snd_ac97_bus **rbus)¶: create an AC97 bus component

Parameters

struct snd_card *card: the card instance
int num: the bus number
const struct snd_ac97_bus_ops *ops: the bus callbacks table
void *private_data: private data pointer for the new instance
struct snd_ac97_bus **rbus: the pointer to store the new AC97 bus instance.

Description

Creates an AC97 bus component. An struct snd_ac97_bus instance is newly allocated and initialized.

The ops table must include valid callbacks (at least read and write). The other callbacks, wait and reset, are not mandatory.

The clock is set to 48000. If another clock is needed, set (*rbus)->clock manually.

The AC97 bus instance is registered as a low-level device, so you don’t have to release it manually.

Return

Zero if successful, or a negative error code on failure.

int snd_ac97_mixer(struct snd_ac97_bus *bus, struct snd_ac97_template *template, struct snd_ac97 **rac97)¶: create an Codec97 component

Parameters

struct snd_ac97_bus *bus: the AC97 bus which codec is attached to
struct snd_ac97_template *template: the template of ac97, including index, callbacks and the private data.
struct snd_ac97 **rac97: the pointer to store the new ac97 instance.

Description

Creates an Codec97 component. An struct snd_ac97 instance is newly allocated and initialized from the template. The codec is then initialized by the standard procedure.

The template must include the codec number (num) and address (addr), and the private data (private_data).

The ac97 instance is registered as a low-level device, so you don’t have to release it manually.

Return

Zero if successful, or a negative error code on failure.

int snd_ac97_update_power(struct snd_ac97 *ac97, int reg, int powerup)¶: update the powerdown register

Parameters

struct snd_ac97 *ac97: the codec instance
int reg: the rate register, e.g. AC97_PCM_FRONT_DAC_RATE
int powerup: non-zero when power up the part

Description

Update the AC97 powerdown register bits of the given part.

Return

Zero.

void snd_ac97_suspend(struct snd_ac97 *ac97)¶: General suspend function for AC97 codec

Parameters

struct snd_ac97 *ac97: the ac97 instance

Description

Suspends the codec, power down the chip.

void snd_ac97_resume(struct snd_ac97 *ac97)¶: General resume function for AC97 codec

Parameters

struct snd_ac97 *ac97: the ac97 instance

Description

Do the standard resume procedure, power up and restoring the old register values.

int snd_ac97_tune_hardware(struct snd_ac97 *ac97, const struct ac97_quirk *quirk, const char *override)¶: tune up the hardware

Parameters

struct snd_ac97 *ac97: the ac97 instance
const struct ac97_quirk *quirk: quirk list
const char *override: explicit quirk value (overrides the list if non-NULL)

Description

Do some workaround for each pci device, such as renaming of the headphone (true line-out) control as “Master”. The quirk-list must be terminated with a zero-filled entry.

Return

Zero if successful, or a negative error code on failure.

int snd_ac97_set_rate(struct snd_ac97 *ac97, int reg, unsigned int rate)¶: change the rate of the given input/output.

Parameters

struct snd_ac97 *ac97: the ac97 instance
int reg: the register to change
unsigned int rate: the sample rate to set

Description

Changes the rate of the given input/output on the codec. If the codec doesn’t support VAR, the rate must be 48000 (except for SPDIF).

The valid registers are AC97_PCM_MIC_ADC_RATE, AC97_PCM_FRONT_DAC_RATE, AC97_PCM_LR_ADC_RATE. AC97_PCM_SURR_DAC_RATE and AC97_PCM_LFE_DAC_RATE are accepted if the codec supports them. AC97_SPDIF is accepted as a pseudo register to modify the SPDIF status bits.

Return

Zero if successful, or a negative error code on failure.

int snd_ac97_pcm_assign(struct snd_ac97_bus *bus, unsigned short pcms_count, const struct ac97_pcm *pcms)¶: assign AC97 slots to given PCM streams

Parameters

struct snd_ac97_bus *bus: the ac97 bus instance
unsigned short pcms_count: count of PCMs to be assigned
const struct ac97_pcm *pcms: PCMs to be assigned

Description

It assigns available AC97 slots for given PCMs. If none or only some slots are available, pcm->xxx.slots and pcm->xxx.rslots[] members are reduced and might be zero.

Return

Zero if successful, or a negative error code on failure.

int snd_ac97_pcm_open(struct ac97_pcm *pcm, unsigned int rate, enum ac97_pcm_cfg cfg, unsigned short slots)¶: opens the given AC97 pcm

Parameters

struct ac97_pcm *pcm: the ac97 pcm instance
unsigned int rate: rate in Hz, if codec does not support VRA, this value must be 48000Hz
enum ac97_pcm_cfg cfg: output stream characteristics
unsigned short slots: a subset of allocated slots (snd_ac97_pcm_assign) for this pcm

Description

It locks the specified slots and sets the given rate to AC97 registers.

Return

Zero if successful, or a negative error code on failure.

int snd_ac97_pcm_close(struct ac97_pcm *pcm)¶: closes the given AC97 pcm

Parameters

struct ac97_pcm *pcm: the ac97 pcm instance

Description

It frees the locked AC97 slots.

Return

Zero.

int snd_ac97_pcm_double_rate_rules(struct snd_pcm_runtime *runtime)¶: set double rate constraints

Parameters

struct snd_pcm_runtime *runtime: the runtime of the ac97 front playback pcm

Description

Installs the hardware constraint rules to prevent using double rates and more than two channels at the same time.

Return

Zero if successful, or a negative error code on failure.

Virtual Master Control API¶

int snd_ctl_add_followers(struct snd_card *card, struct snd_kcontrol *master, const char *const *list)¶: add multiple followers to vmaster

Parameters

struct snd_card *card: card instance
struct snd_kcontrol *master: the target vmaster kcontrol object
const char * const *list: NULL-terminated list of name strings of followers to be added

Description

Adds the multiple follower kcontrols with the given names. Returns 0 for success or a negative error code.

struct snd_kcontrol *snd_ctl_make_virtual_master(char *name, const unsigned int *tlv)¶: Create a virtual master control

Parameters

char *name: name string of the control element to create
const unsigned int *tlv: optional TLV int array for dB information

Description

Creates a virtual master control with the given name string.

After creating a vmaster element, you can add the follower controls via snd_ctl_add_follower() or snd_ctl_add_follower_uncached().

The optional argument tlv can be used to specify the TLV information for dB scale of the master control. It should be a single element with #SNDRV_CTL_TLVT_DB_SCALE, #SNDRV_CTL_TLV_DB_MINMAX or #SNDRV_CTL_TLVT_DB_MINMAX_MUTE type, and should be the max 0dB.

Return

The created control element, or NULL for errors (ENOMEM).

int snd_ctl_add_vmaster_hook(struct snd_kcontrol *kcontrol, void (*hook)(void *private_data, int), void *private_data)¶: Add a hook to a vmaster control

Parameters

struct snd_kcontrol *kcontrol: vmaster kctl element
void (*hook)(void *private_data, int): the hook function
void *private_data: the private_data pointer to be saved

Description

Adds the given hook to the vmaster control element so that it’s called at each time when the value is changed.

Return

Zero.

void snd_ctl_sync_vmaster(struct snd_kcontrol *kcontrol, bool hook_only)¶: Sync the vmaster followers and hook

Parameters

struct snd_kcontrol *kcontrol: vmaster kctl element
bool hook_only: sync only the hook

Description

Forcibly call the put callback of each follower and call the hook function to synchronize with the current value of the given vmaster element. NOP when NULL is passed to kcontrol.

int snd_ctl_apply_vmaster_followers(struct snd_kcontrol *kctl, int (*func)(struct snd_kcontrol *vfollower, struct snd_kcontrol *follower, void *arg), void *arg)¶: Apply function to each vmaster follower

Parameters

struct snd_kcontrol *kctl: vmaster kctl element
int (*func)(struct snd_kcontrol *vfollower, struct snd_kcontrol *follower, void *arg): function to apply
void *arg: optional function argument

Description

Apply the function func to each follower kctl of the given vmaster kctl.

Return

0 if successful, or a negative error code

struct snd_kcontrol *snd_ctl_find_id_mixer(struct snd_card *card, const char *name)¶: find the control instance with the given name string

Parameters

struct snd_card *card: the card instance
const char *name: the name string

Description

Finds the control instance with the given name and SNDRV_CTL_ELEM_IFACE_MIXER. Other fields are set to zero.

This is merely a wrapper to snd_ctl_find_id().

Return

The pointer of the instance if found, or NULL if not.

struct snd_kcontrol *snd_ctl_find_id_mixer_locked(struct snd_card *card, const char *name)¶: find the control instance with the given name string

Parameters

struct snd_card *card: the card instance
const char *name: the name string

Description

Finds the control instance with the given name and SNDRV_CTL_ELEM_IFACE_MIXER. Other fields are set to zero.

This is merely a wrapper to snd_ctl_find_id_locked(). The caller must down card->controls_rwsem before calling this function.

Return

The pointer of the instance if found, or NULL if not.

int snd_ctl_add_follower(struct snd_kcontrol *master, struct snd_kcontrol *follower)¶: Add a virtual follower control

Parameters

struct snd_kcontrol *master: vmaster element
struct snd_kcontrol *follower: follower element to add

Description

Add a virtual follower control to the given master element created via snd_ctl_create_virtual_master() beforehand.

All followers must be the same type (returning the same information via info callback). The function doesn’t check it, so it’s your responsibility.

Also, some additional limitations: at most two channels, logarithmic volume control (dB level) thus no linear volume, master can only attenuate the volume without gain

Return

Zero if successful or a negative error code.

int snd_ctl_add_follower_uncached(struct snd_kcontrol *master, struct snd_kcontrol *follower)¶: Add a virtual follower control

Parameters

struct snd_kcontrol *master: vmaster element
struct snd_kcontrol *follower: follower element to add

Description

Add a virtual follower control to the given master. Unlike snd_ctl_add_follower(), the element added via this function is supposed to have volatile values, and get callback is called at each time queried from the master.

When the control peeks the hardware values directly and the value can be changed by other means than the put callback of the element, this function should be used to keep the value always up-to-date.

Return

Zero if successful or a negative error code.

MIDI API¶

Raw MIDI API¶

int snd_rawmidi_receive(struct snd_rawmidi_substream *substream, const unsigned char *buffer, int count)¶: receive the input data from the device

Parameters

struct snd_rawmidi_substream *substream: the rawmidi substream
const unsigned char *buffer: the buffer pointer
int count: the data size to read

Description

Reads the data from the internal buffer.

Return

The size of read data, or a negative error code on failure.

int snd_rawmidi_transmit_empty(struct snd_rawmidi_substream *substream)¶: check whether the output buffer is empty

Parameters

struct snd_rawmidi_substream *substream: the rawmidi substream

Return

1 if the internal output buffer is empty, 0 if not.

int snd_rawmidi_transmit_peek(struct snd_rawmidi_substream *substream, unsigned char *buffer, int count)¶: copy data from the internal buffer

Parameters

struct snd_rawmidi_substream *substream: the rawmidi substream
unsigned char *buffer: the buffer pointer
int count: data size to transfer

Description

Copies data from the internal output buffer to the given buffer.

Call this in the interrupt handler when the midi output is ready, and call snd_rawmidi_transmit_ack() after the transmission is finished.

Return

The size of copied data, or a negative error code on failure.

int snd_rawmidi_transmit_ack(struct snd_rawmidi_substream *substream, int count)¶: acknowledge the transmission

Parameters

struct snd_rawmidi_substream *substream: the rawmidi substream
int count: the transferred count

Description

Advances the hardware pointer for the internal output buffer with the given size and updates the condition. Call after the transmission is finished.

Return

The advanced size if successful, or a negative error code on failure.

int snd_rawmidi_transmit(struct snd_rawmidi_substream *substream, unsigned char *buffer, int count)¶: copy from the buffer to the device

Parameters

struct snd_rawmidi_substream *substream: the rawmidi substream
unsigned char *buffer: the buffer pointer
int count: the data size to transfer

Description

Copies data from the buffer to the device and advances the pointer.

Return

The copied size if successful, or a negative error code on failure.

int snd_rawmidi_proceed(struct snd_rawmidi_substream *substream)¶: Discard the all pending bytes and proceed

Parameters

struct snd_rawmidi_substream *substream: rawmidi substream

Return

the number of discarded bytes

int snd_rawmidi_new(struct snd_card *card, char *id, int device, int output_count, int input_count, struct snd_rawmidi **rrawmidi)¶: create a rawmidi instance

Parameters

struct snd_card *card: the card instance
char *id: the id string
int device: the device index
int output_count: the number of output streams
int input_count: the number of input streams
struct snd_rawmidi **rrawmidi: the pointer to store the new rawmidi instance

Description

Creates a new rawmidi instance. Use snd_rawmidi_set_ops() to set the operators to the new instance.

Return

Zero if successful, or a negative error code on failure.

void snd_rawmidi_set_ops(struct snd_rawmidi *rmidi, int stream, const struct snd_rawmidi_ops *ops)¶: set the rawmidi operators

Parameters

struct snd_rawmidi *rmidi: the rawmidi instance
int stream: the stream direction, SNDRV_RAWMIDI_STREAM_XXX
const struct snd_rawmidi_ops *ops: the operator table

Description

Sets the rawmidi operators for the given stream direction.

MPU401-UART API¶

irqreturn_t snd_mpu401_uart_interrupt(int irq, void *dev_id)¶: generic MPU401-UART interrupt handler

Parameters

int irq: the irq number
void *dev_id: mpu401 instance

Description

Processes the interrupt for MPU401-UART i/o.

Return

IRQ_HANDLED if the interrupt was handled. IRQ_NONE otherwise.

irqreturn_t snd_mpu401_uart_interrupt_tx(int irq, void *dev_id)¶: generic MPU401-UART transmit irq handler

Parameters

int irq: the irq number
void *dev_id: mpu401 instance

Description

Processes the interrupt for MPU401-UART output.

Return

IRQ_HANDLED if the interrupt was handled. IRQ_NONE otherwise.

int snd_mpu401_uart_new(struct snd_card *card, int device, unsigned short hardware, unsigned long port, unsigned int info_flags, int irq, struct snd_rawmidi **rrawmidi)¶: create an MPU401-UART instance

Parameters

struct snd_card *card: the card instance
int device: the device index, zero-based
unsigned short hardware: the hardware type, MPU401_HW_XXXX
unsigned long port: the base address of MPU401 port
unsigned int info_flags: bitflags MPU401_INFO_XXX
int irq: the ISA irq number, -1 if not to be allocated
struct snd_rawmidi ** rrawmidi: the pointer to store the new rawmidi instance

Description

Creates a new MPU-401 instance.

Note that the rawmidi instance is returned on the rrawmidi argument, not the mpu401 instance itself. To access to the mpu401 instance, cast from rawmidi->private_data (with struct snd_mpu401 magic-cast).

Return

Zero if successful, or a negative error code.

Proc Info API¶

Proc Info Interface¶

int snd_info_get_line(struct snd_info_buffer *buffer, char *line, int len)¶: read one line from the procfs buffer

Parameters

struct snd_info_buffer *buffer: the procfs buffer
char *line: the buffer to store
int len: the max. buffer size

Description

Reads one line from the buffer and stores the string.

Return

Zero if successful, or 1 if error or EOF.

const char *snd_info_get_str(char *dest, const char *src, int len)¶: parse a string token

Parameters

char *dest: the buffer to store the string token
const char *src: the original string
int len: the max. length of token - 1

Description

Parses the original string and copy a token to the given string buffer.

Return

The updated pointer of the original string so that it can be used for the next call.

struct snd_info_entry *snd_info_create_module_entry(struct module *module, const char *name, struct snd_info_entry *parent)¶: create an info entry for the given module

Parameters

struct module * module: the module pointer
const char *name: the file name
struct snd_info_entry *parent: the parent directory

Description

Creates a new info entry and assigns it to the given module.

Return

The pointer of the new instance, or NULL on failure.

struct snd_info_entry *snd_info_create_card_entry(struct snd_card *card, const char *name, struct snd_info_entry *parent)¶: create an info entry for the given card

Parameters

struct snd_card *card: the card instance
const char *name: the file name
struct snd_info_entry * parent: the parent directory

Description

Creates a new info entry and assigns it to the given card.

Return

The pointer of the new instance, or NULL on failure.

void snd_info_free_entry(struct snd_info_entry *entry)¶: release the info entry

Parameters

struct snd_info_entry * entry: the info entry

Description

Releases the info entry.

int snd_info_register(struct snd_info_entry *entry)¶: register the info entry

Parameters

struct snd_info_entry *entry: the info entry

Description

Registers the proc info entry. The all children entries are registered recursively.

Return

Zero if successful, or a negative error code on failure.

int snd_card_rw_proc_new(struct snd_card *card, const char *name, void *private_data, void (*read)(struct snd_info_entry*, struct snd_info_buffer*), void (*write)(struct snd_info_entry *entry, struct snd_info_buffer *buffer))¶: Create a read/write text proc file entry for the card

Parameters

struct snd_card *card: the card instance
const char *name: the file name
void *private_data: the arbitrary private data
void (*read)(struct snd_info_entry *, struct snd_info_buffer *): the read callback
void (*write)(struct snd_info_entry *entry, struct snd_info_buffer *buffer): the write callback, NULL for read-only

Description

This proc file entry will be registered via snd_card_register() call, and it will be removed automatically at the card removal, too.

Return

zero if successful, or a negative error code

Compress Offload¶

Compress Offload API¶

int snd_compr_stop_error(struct snd_compr_stream *stream, snd_pcm_state_t state)¶: Report a fatal error on a stream

Parameters

struct snd_compr_stream *stream: pointer to stream
snd_pcm_state_t state: state to transition the stream to

Description

Stop the stream and set its state.

Should be called with compressed device lock held.

Return

zero if successful, or a negative error code

int snd_compress_new(struct snd_card *card, int device, int dirn, const char *id, struct snd_compr *compr)¶: create new compress device

Parameters

struct snd_card *card: sound card pointer
int device: device number
int dirn: device direction, should be of type enum snd_compr_direction
const char *id: ID string
struct snd_compr *compr: compress device pointer

Return

zero if successful, or a negative error code

struct snd_compressed_buffer¶: compressed buffer

Definition:

struct snd_compressed_buffer {
    __u32 fragment_size;
    __u32 fragments;
};

Members

fragment_size: size of buffer fragment in bytes
fragments: number of such fragments

struct snd_compr_params¶: compressed stream params

Definition:

struct snd_compr_params {
    struct snd_compressed_buffer buffer;
    struct snd_codec codec;
    __u8 no_wake_mode;
};

Members

buffer: buffer description
codec: codec parameters
no_wake_mode: dont wake on fragment elapsed

struct snd_compr_tstamp¶: timestamp descriptor

Definition:

struct snd_compr_tstamp {
    __u32 byte_offset;
    __u32 copied_total;
    __u32 pcm_frames;
    __u32 pcm_io_frames;
    __u32 sampling_rate;
};

Members

byte_offset: Byte offset in ring buffer to DSP
copied_total: Total number of bytes copied from/to ring buffer to/by DSP
pcm_frames: Frames decoded or encoded by DSP. This field will evolve by large steps and should only be used to monitor encoding/decoding progress. It shall not be used for timing estimates.
pcm_io_frames: Frames rendered or received by DSP into a mixer or an audio output/input. This field should be used for A/V sync or time estimates.
sampling_rate: sampling rate of audio

struct snd_compr_avail¶: avail descriptor

Definition:

struct snd_compr_avail {
    __u64 avail;
    struct snd_compr_tstamp tstamp;
};

Members

avail: Number of bytes available in ring buffer for writing/reading
tstamp: timestamp information

struct snd_compr_caps¶: caps descriptor

Definition:

struct snd_compr_caps {
    __u32 num_codecs;
    __u32 direction;
    __u32 min_fragment_size;
    __u32 max_fragment_size;
    __u32 min_fragments;
    __u32 max_fragments;
    __u32 codecs[MAX_NUM_CODECS];
    __u32 reserved[11];
};

Members

num_codecs: number of codecs supported
direction: direction supported. Of type snd_compr_direction
min_fragment_size: minimum fragment supported by DSP
max_fragment_size: maximum fragment supported by DSP
min_fragments: min fragments supported by DSP
max_fragments: max fragments supported by DSP
codecs: pointer to array of codecs
reserved: reserved field

struct snd_compr_codec_caps¶: query capability of codec

Definition:

struct snd_compr_codec_caps {
    __u32 codec;
    __u32 num_descriptors;
    struct snd_codec_desc descriptor[MAX_NUM_CODEC_DESCRIPTORS];
};

Members

codec: codec for which capability is queried
num_descriptors: number of codec descriptors
descriptor: array of codec capability descriptor

enum sndrv_compress_encoder¶: encoder metadata key

Constants

SNDRV_COMPRESS_ENCODER_PADDING: no of samples appended by the encoder at the end of the track
SNDRV_COMPRESS_ENCODER_DELAY: no of samples inserted by the encoder at the beginning of the track

struct snd_compr_metadata¶: compressed stream metadata

Definition:

struct snd_compr_metadata {
    __u32 key;
    __u32 value[8];
};

Members

key: key id
value: key value

struct snd_enc_vorbis¶: Vorbis encoder parameters

Definition:

struct snd_enc_vorbis {
    __s32 quality;
    __u32 managed;
    __u32 max_bit_rate;
    __u32 min_bit_rate;
    __u32 downmix;
};

Members

quality: Sets encoding quality to n, between -1 (low) and 10 (high). In the default mode of operation, the quality level is 3. Normal quality range is 0 - 10.
managed: Boolean. Set bitrate management mode. This turns off the normal VBR encoding, but allows hard or soft bitrate constraints to be enforced by the encoder. This mode can be slower, and may also be lower quality. It is primarily useful for streaming.
max_bit_rate: Enabled only if managed is TRUE
min_bit_rate: Enabled only if managed is TRUE
downmix: Boolean. Downmix input from stereo to mono (has no effect on non-stereo streams). Useful for lower-bitrate encoding.

Description

These options were extracted from the OpenMAX IL spec and Gstreamer vorbisenc properties

For best quality users should specify VBR mode and set quality levels.

struct snd_enc_real¶: RealAudio encoder parameters

Definition:

struct snd_enc_real {
    __u32 quant_bits;
    __u32 start_region;
    __u32 num_regions;
};

Members

quant_bits: number of coupling quantization bits in the stream
start_region: coupling start region in the stream
num_regions: number of regions value

Description

These options were extracted from the OpenMAX IL spec

struct snd_enc_flac¶: FLAC encoder parameters

Definition:

struct snd_enc_flac {
    __u32 num;
    __u32 gain;
};

Members

num: serial number, valid only for OGG formats needs to be set by application
gain: Add replay gain tags

Description

These options were extracted from the FLAC online documentation at http://flac.sourceforge.net/documentation_tools_flac.html

To make the API simpler, it is assumed that the user will select quality profiles. Additional options that affect encoding quality and speed can be added at a later stage if needed.

By default the Subset format is used by encoders.

TAGS such as pictures, etc, cannot be handled by an offloaded encoder and are not supported in this API.

struct snd_compr_runtime¶: runtime stream description

Definition:

struct snd_compr_runtime {
    snd_pcm_state_t state;
    struct snd_compr_ops *ops;
    void *buffer;
    u64 buffer_size;
    u32 fragment_size;
    u32 fragments;
    u64 total_bytes_available;
    u64 total_bytes_transferred;
    wait_queue_head_t sleep;
    void *private_data;
    unsigned char *dma_area;
    dma_addr_t dma_addr;
    size_t dma_bytes;
    struct snd_dma_buffer *dma_buffer_p;
};

Members

state: stream state
ops: pointer to DSP callbacks
buffer: pointer to kernel buffer, valid only when not in mmap mode or DSP doesn’t implement copy
buffer_size: size of the above buffer
fragment_size: size of buffer fragment in bytes
fragments: number of such fragments
total_bytes_available: cumulative number of bytes made available in the ring buffer
total_bytes_transferred: cumulative bytes transferred by offload DSP
sleep: poll sleep
private_data: driver private data pointer
dma_area: virtual buffer address
dma_addr: physical buffer address (not accessible from main CPU)
dma_bytes: size of DMA area
dma_buffer_p: runtime dma buffer pointer

struct snd_compr_stream¶: compressed stream

Definition:

struct snd_compr_stream {
    const char *name;
    struct snd_compr_ops *ops;
    struct snd_compr_runtime *runtime;
    struct snd_compr *device;
    struct delayed_work error_work;
    enum snd_compr_direction direction;
    bool metadata_set;
    bool next_track;
    bool partial_drain;
    bool pause_in_draining;
    void *private_data;
    struct snd_dma_buffer dma_buffer;
};

Members

name: device name
ops: pointer to DSP callbacks
runtime: pointer to runtime structure
device: device pointer
error_work: delayed work used when closing the stream due to an error
direction: stream direction, playback/recording
metadata_set: metadata set flag, true when set
next_track: has userspace signal next track transition, true when set
partial_drain: undergoing partial_drain for stream, true when set
pause_in_draining: paused during draining state, true when set
private_data: pointer to DSP private data
dma_buffer: allocated buffer if any

struct snd_compr_ops¶: compressed path DSP operations

Definition:

struct snd_compr_ops {
    int (*open)(struct snd_compr_stream *stream);
    int (*free)(struct snd_compr_stream *stream);
    int (*set_params)(struct snd_compr_stream *stream, struct snd_compr_params *params);
    int (*get_params)(struct snd_compr_stream *stream, struct snd_codec *params);
    int (*set_metadata)(struct snd_compr_stream *stream, struct snd_compr_metadata *metadata);
    int (*get_metadata)(struct snd_compr_stream *stream, struct snd_compr_metadata *metadata);
    int (*trigger)(struct snd_compr_stream *stream, int cmd);
    int (*pointer)(struct snd_compr_stream *stream, struct snd_compr_tstamp *tstamp);
    int (*copy)(struct snd_compr_stream *stream, char __user *buf, size_t count);
    int (*mmap)(struct snd_compr_stream *stream, struct vm_area_struct *vma);
    int (*ack)(struct snd_compr_stream *stream, size_t bytes);
    int (*get_caps) (struct snd_compr_stream *stream, struct snd_compr_caps *caps);
    int (*get_codec_caps) (struct snd_compr_stream *stream, struct snd_compr_codec_caps *codec);
};

Members

open: Open the compressed stream This callback is mandatory and shall keep dsp ready to receive the stream parameter
free: Close the compressed stream, mandatory
set_params: Sets the compressed stream parameters, mandatory This can be called in during stream creation only to set codec params and the stream properties
get_params: retrieve the codec parameters, mandatory
set_metadata: Set the metadata values for a stream
get_metadata: retrieves the requested metadata values from stream
trigger: Trigger operations like start, pause, resume, drain, stop. This callback is mandatory
pointer: Retrieve current h/w pointer information. Mandatory
copy: Copy the compressed data to/from userspace, Optional Can’t be implemented if DSP supports mmap
mmap: DSP mmap method to mmap DSP memory
ack: Ack for DSP when data is written to audio buffer, Optional Not valid if copy is implemented
get_caps: Retrieve DSP capabilities, mandatory
get_codec_caps: Retrieve capabilities for a specific codec, mandatory

struct snd_compr¶: Compressed device

Definition:

struct snd_compr {
    const char *name;
    struct device *dev;
    struct snd_compr_ops *ops;
    void *private_data;
    struct snd_card *card;
    unsigned int direction;
    struct mutex lock;
    int device;
    bool use_pause_in_draining;
#ifdef CONFIG_SND_VERBOSE_PROCFS;
};

Members

name: DSP device name
dev: associated device instance
ops: pointer to DSP callbacks
private_data: pointer to DSP pvt data
card: sound card pointer
direction: Playback or capture direction
lock: device lock
device: device id
use_pause_in_draining: allow pause in draining, true when set

void snd_compr_use_pause_in_draining(struct snd_compr_stream *substream)¶: Allow pause and resume in draining state

Parameters

struct snd_compr_stream *substream: compress substream to set

Description

Allow pause and resume in draining state. Only HW driver supports this transition can call this API.

void snd_compr_set_runtime_buffer(struct snd_compr_stream *stream, struct snd_dma_buffer *bufp)¶: Set the Compress runtime buffer

Parameters

struct snd_compr_stream *stream: compress stream to set
struct snd_dma_buffer *bufp: the buffer information, NULL to clear

Description

Copy the buffer information to runtime buffer when bufp is non-NULL. Otherwise it clears the current buffer information.

ASoC¶

ASoC Core API¶

struct snd_soc_component *snd_soc_kcontrol_component(struct snd_kcontrol *kcontrol)¶: Returns the component that registered the control

Parameters

struct snd_kcontrol *kcontrol: The control for which to get the component

Note

This function will work correctly if the control has been registered for a component. With snd_soc_add_codec_controls() or via table based setup for either a CODEC or component driver. Otherwise the behavior is undefined.

struct snd_soc_dai *snd_soc_find_dai(const struct snd_soc_dai_link_component *dlc)¶: Find a registered DAI

Parameters

const struct snd_soc_dai_link_component *dlc: name of the DAI or the DAI driver and optional component info to match

Description

This function will search all registered components and their DAIs to find the DAI of the same name. The component’s of_node and name should also match if being specified.

Return

pointer of DAI, or NULL if not found.

void snd_soc_remove_pcm_runtime(struct snd_soc_card *card, struct snd_soc_pcm_runtime *rtd)¶: Remove a pcm_runtime from card

Parameters

struct snd_soc_card *card: The ASoC card to which the pcm_runtime has
struct snd_soc_pcm_runtime *rtd: The pcm_runtime to remove

Description

This function removes a pcm_runtime from the ASoC card.

int snd_soc_add_pcm_runtime(struct snd_soc_card *card, struct snd_soc_dai_link *dai_link)¶: Add a pcm_runtime dynamically via dai_link

Parameters

struct snd_soc_card *card: The ASoC card to which the pcm_runtime is added
struct snd_soc_dai_link *dai_link: The DAI link to find pcm_runtime

Description

This function adds a pcm_runtime ASoC card by using dai_link.

Note

Topology can use this API to add pcm_runtime when probing the topology component. And machine drivers can still define static DAI links in dai_link array.

int snd_soc_runtime_set_dai_fmt(struct snd_soc_pcm_runtime *rtd, unsigned int dai_fmt)¶: Change DAI link format for a ASoC runtime

Parameters

struct snd_soc_pcm_runtime *rtd: The runtime for which the DAI link format should be changed
unsigned int dai_fmt: The new DAI link format

Description

This function updates the DAI link format for all DAIs connected to the DAI link for the specified runtime.

Returns 0 on success, otherwise a negative error code.

Note

For setups with a static format set the dai_fmt field in the corresponding snd_dai_link struct instead of using this function.

int snd_soc_set_dmi_name(struct snd_soc_card *card, const char *flavour)¶: Register DMI names to card

Parameters

struct snd_soc_card *card: The card to register DMI names
const char *flavour: The flavour “differentiator” for the card amongst its peers.

Description

An Intel machine driver may be used by many different devices but are difficult for userspace to differentiate, since machine drivers usually use their own name as the card short name and leave the card long name blank. To differentiate such devices and fix bugs due to lack of device-specific configurations, this function allows DMI info to be used as the sound card long name, in the format of “vendor-product-version-board” (Character ‘-’ is used to separate different DMI fields here). This will help the user space to load the device-specific Use Case Manager (UCM) configurations for the card.

Possible card long names may be: DellInc.-XPS139343-01-0310JH ASUSTeKCOMPUTERINC.-T100TA-1.0-T100TA Circuitco-MinnowboardMaxD0PLATFORM-D0-MinnowBoardMAX

This function also supports flavoring the card longname to provide the extra differentiation, like “vendor-product-version-board-flavor”.

We only keep number and alphabet characters and a few separator characters in the card long name since UCM in the user space uses the card long names as card configuration directory names and AudoConf cannot support special characters like SPACE.

Returns 0 on success, otherwise a negative error code.

struct snd_kcontrol *snd_soc_cnew(const struct snd_kcontrol_new *_template, void *data, const char *long_name, const char *prefix)¶: create new control

Parameters

const struct snd_kcontrol_new *_template: control template
void *data: control private data
const char *long_name: control long name
const char *prefix: control name prefix

Description

Create a new mixer control from a template control.

Returns 0 for success, else error.

int snd_soc_add_component_controls(struct snd_soc_component *component, const struct snd_kcontrol_new *controls, unsigned int num_controls)¶: Add an array of controls to a component.

Parameters

struct snd_soc_component *component: Component to add controls to
const struct snd_kcontrol_new *controls: Array of controls to add
unsigned int num_controls: Number of elements in the array

Return

0 for success, else error.

int snd_soc_add_card_controls(struct snd_soc_card *soc_card, const struct snd_kcontrol_new *controls, int num_controls)¶: add an array of controls to a SoC card. Convenience function to add a list of controls.

Parameters

struct snd_soc_card *soc_card: SoC card to add controls to
const struct snd_kcontrol_new *controls: array of controls to add
int num_controls: number of elements in the array

Description

Return 0 for success, else error.

int snd_soc_add_dai_controls(struct snd_soc_dai *dai, const struct snd_kcontrol_new *controls, int num_controls)¶: add an array of controls to a DAI. Convenience function to add a list of controls.

Parameters

struct snd_soc_dai *dai: DAI to add controls to
const struct snd_kcontrol_new *controls: array of controls to add
int num_controls: number of elements in the array

Description

Return 0 for success, else error.

int snd_soc_register_card(struct snd_soc_card *card)¶: Register a card with the ASoC core

Parameters

struct snd_soc_card *card: Card to register

void snd_soc_unregister_card(struct snd_soc_card *card)¶: Unregister a card with the ASoC core

Parameters

struct snd_soc_card *card: Card to unregister

struct snd_soc_dai *snd_soc_register_dai(struct snd_soc_component *component, struct snd_soc_dai_driver *dai_drv, bool legacy_dai_naming)¶: Register a DAI dynamically & create its widgets

Parameters

struct snd_soc_component *component: The component the DAIs are registered for
struct snd_soc_dai_driver *dai_drv: DAI driver to use for the DAI
bool legacy_dai_naming: if true, use legacy single-name format; if false, use multiple-name format;

Description

Topology can use this API to register DAIs when probing a component. These DAIs’s widgets will be freed in the card cleanup and the DAIs will be freed in the component cleanup.

void snd_soc_unregister_dais(struct snd_soc_component *component)¶: Unregister DAIs from the ASoC core

Parameters

struct snd_soc_component *component: The component for which the DAIs should be unregistered

int snd_soc_register_dais(struct snd_soc_component *component, struct snd_soc_dai_driver *dai_drv, size_t count)¶: Register a DAI with the ASoC core

Parameters

struct snd_soc_component *component: The component the DAIs are registered for
struct snd_soc_dai_driver *dai_drv: DAI driver to use for the DAIs
size_t count: Number of DAIs

void snd_soc_unregister_component_by_driver(struct device *dev, const struct snd_soc_component_driver *component_driver)¶: Unregister component using a given driver from the ASoC core

Parameters

struct device *dev: The device to unregister
const struct snd_soc_component_driver *component_driver: The component driver to unregister

void snd_soc_unregister_component(struct device *dev)¶: Unregister all related component from the ASoC core

Parameters

struct device *dev: The device to unregister

struct snd_soc_dai *devm_snd_soc_register_dai(struct device *dev, struct snd_soc_component *component, struct snd_soc_dai_driver *dai_drv, bool legacy_dai_naming)¶: resource-managed dai registration

Parameters

struct device *dev: Device used to manage component
struct snd_soc_component *component: The component the DAIs are registered for
struct snd_soc_dai_driver *dai_drv: DAI driver to use for the DAI
bool legacy_dai_naming: if true, use legacy single-name format; if false, use multiple-name format;

int devm_snd_soc_register_component(struct device *dev, const struct snd_soc_component_driver *cmpnt_drv, struct snd_soc_dai_driver *dai_drv, int num_dai)¶: resource managed component registration

Parameters

struct device *dev: Device used to manage component
const struct snd_soc_component_driver *cmpnt_drv: Component driver
struct snd_soc_dai_driver *dai_drv: DAI driver
int num_dai: Number of DAIs to register

Description

Register a component with automatic unregistration when the device is unregistered.

int devm_snd_soc_register_card(struct device *dev, struct snd_soc_card *card)¶: resource managed card registration

Parameters

struct device *dev: Device used to manage card
struct snd_soc_card *card: Card to register

Description

Register a card with automatic unregistration when the device is unregistered.

int devm_snd_dmaengine_pcm_register(struct device *dev, const struct snd_dmaengine_pcm_config *config, unsigned int flags)¶: resource managed dmaengine PCM registration

Parameters

struct device *dev: The parent device for the PCM device
const struct snd_dmaengine_pcm_config *config: Platform specific PCM configuration
unsigned int flags: Platform specific quirks

Description

Register a dmaengine based PCM device with automatic unregistration when the device is unregistered.

int snd_soc_component_set_sysclk(struct snd_soc_component *component, int clk_id, int source, unsigned int freq, int dir)¶: configure COMPONENT system or master clock.

Parameters

struct snd_soc_component *component: COMPONENT
int clk_id: DAI specific clock ID
int source: Source for the clock
unsigned int freq: new clock frequency in Hz
int dir: new clock direction - input/output.

Description

Configures the CODEC master (MCLK) or system (SYSCLK) clocking.

int snd_soc_component_set_jack(struct snd_soc_component *component, struct snd_soc_jack *jack, void *data)¶: configure component jack.

Parameters

struct snd_soc_component *component: COMPONENTs
struct snd_soc_jack *jack: structure to use for the jack
void *data: can be used if codec driver need extra data for configuring jack

Description

Configures and enables jack detection function.

int snd_soc_component_get_jack_type(struct snd_soc_component *component)¶

Parameters

struct snd_soc_component *component: COMPONENTs

Description

Returns the jack type of the component This can either be the supported type or one read from devicetree with the property: jack-type.

void snd_soc_component_init_regmap(struct snd_soc_component *component, struct regmap *regmap)¶: Initialize regmap instance for the component

Parameters

struct snd_soc_component *component: The component for which to initialize the regmap instance
struct regmap *regmap: The regmap instance that should be used by the component

Description

This function allows deferred assignment of the regmap instance that is associated with the component. Only use this if the regmap instance is not yet ready when the component is registered. The function must also be called before the first IO attempt of the component.

void snd_soc_component_exit_regmap(struct snd_soc_component *component)¶: De-initialize regmap instance for the component

Parameters

struct snd_soc_component *component: The component for which to de-initialize the regmap instance

Description

Calls regmap_exit() on the regmap instance associated to the component and removes the regmap instance from the component.

This function should only be used if snd_soc_component_init_regmap() was used to initialize the regmap instance.

unsigned int snd_soc_component_read(struct snd_soc_component *component, unsigned int reg)¶: Read register value

Parameters

struct snd_soc_component *component: Component to read from
unsigned int reg: Register to read

Return

read value

int snd_soc_component_write(struct snd_soc_component *component, unsigned int reg, unsigned int val)¶: Write register value

Parameters

struct snd_soc_component *component: Component to write to
unsigned int reg: Register to write
unsigned int val: Value to write to the register

Return

0 on success, a negative error code otherwise.

int snd_soc_component_update_bits(struct snd_soc_component *component, unsigned int reg, unsigned int mask, unsigned int val)¶: Perform read/modify/write cycle

Parameters

struct snd_soc_component *component: Component to update
unsigned int reg: Register to update
unsigned int mask: Mask that specifies which bits to update
unsigned int val: New value for the bits specified by mask

Return

1 if the operation was successful and the value of the register changed, 0 if the operation was successful, but the value did not change. Returns a negative error code otherwise.

int snd_soc_component_update_bits_async(struct snd_soc_component *component, unsigned int reg, unsigned int mask, unsigned int val)¶: Perform asynchronous read/modify/write cycle

Parameters

struct snd_soc_component *component: Component to update
unsigned int reg: Register to update
unsigned int mask: Mask that specifies which bits to update
unsigned int val: New value for the bits specified by mask

Description

This function is similar to snd_soc_component_update_bits(), but the update operation is scheduled asynchronously. This means it may not be completed when the function returns. To make sure that all scheduled updates have been completed snd_soc_component_async_complete() must be called.

Return

1 if the operation was successful and the value of the register changed, 0 if the operation was successful, but the value did not change. Returns a negative error code otherwise.

unsigned int snd_soc_component_read_field(struct snd_soc_component *component, unsigned int reg, unsigned int mask)¶: Read register field value

Parameters

struct snd_soc_component *component: Component to read from
unsigned int reg: Register to read
unsigned int mask: mask of the register field

Return

read value of register field.

int snd_soc_component_write_field(struct snd_soc_component *component, unsigned int reg, unsigned int mask, unsigned int val)¶: write to register field

Parameters

struct snd_soc_component *component: Component to write to
unsigned int reg: Register to write
unsigned int mask: mask of the register field to update
unsigned int val: value of the field to write

Return

1 for change, otherwise 0.

void snd_soc_component_async_complete(struct snd_soc_component *component)¶: Ensure asynchronous I/O has completed

Parameters

struct snd_soc_component *component: Component for which to wait

Description

This function blocks until all asynchronous I/O which has previously been scheduled using snd_soc_component_update_bits_async() has completed.

int snd_soc_component_test_bits(struct snd_soc_component *component, unsigned int reg, unsigned int mask, unsigned int value)¶: Test register for change

Parameters

struct snd_soc_component *component: component
unsigned int reg: Register to test
unsigned int mask: Mask that specifies which bits to test
unsigned int value: Value to test against

Description

Tests a register with a new value and checks if the new value is different from the old value.

Return

1 for change, otherwise 0.

void snd_soc_runtime_action(struct snd_soc_pcm_runtime *rtd, int stream, int action)¶: Increment/Decrement active count for PCM runtime components

Parameters

struct snd_soc_pcm_runtime *rtd: ASoC PCM runtime that is activated
int stream: Direction of the PCM stream
int action: Activate stream if 1. Deactivate if -1.

Description

Increments/Decrements the active count for all the DAIs and components attached to a PCM runtime. Should typically be called when a stream is opened.

Must be called with the rtd->card->pcm_mutex being held

bool snd_soc_runtime_ignore_pmdown_time(struct snd_soc_pcm_runtime *rtd)¶: Check whether to ignore the power down delay

Parameters

struct snd_soc_pcm_runtime *rtd: The ASoC PCM runtime that should be checked.

Description

This function checks whether the power down delay should be ignored for a specific PCM runtime. Returns true if the delay is 0, if the DAI link has been configured to ignore the delay, or if none of the components benefits from having the delay.

int snd_soc_set_runtime_hwparams(struct snd_pcm_substream *substream, const struct snd_pcm_hardware *hw)¶: set the runtime hardware parameters

Parameters

struct snd_pcm_substream *substream: the pcm substream
const struct snd_pcm_hardware *hw: the hardware parameters

Description

Sets the substream runtime hardware parameters.

int snd_soc_runtime_calc_hw(struct snd_soc_pcm_runtime *rtd, struct snd_pcm_hardware *hw, int stream)¶: Calculate hw limits for a PCM stream

Parameters

struct snd_soc_pcm_runtime *rtd: ASoC PCM runtime
struct snd_pcm_hardware *hw: PCM hardware parameters (output)
int stream: Direction of the PCM stream

Description

Calculates the subset of stream parameters supported by all DAIs associated with the PCM stream.

int snd_soc_info_enum_double(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_info *uinfo)¶: enumerated double mixer info callback

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_info *uinfo: control element information

Description

Callback to provide information about a double enumerated mixer control.

Returns 0 for success.

int snd_soc_get_enum_double(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: enumerated double mixer get callback

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback to get the value of a double enumerated mixer.

Returns 0 for success.

int snd_soc_put_enum_double(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: enumerated double mixer put callback

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback to set the value of a double enumerated mixer.

Returns 0 for success.

int snd_soc_read_signed(struct snd_soc_component *component, unsigned int reg, unsigned int mask, unsigned int shift, unsigned int sign_bit, int *signed_val)¶: Read a codec register and interpret as signed value

Parameters

struct snd_soc_component *component: component
unsigned int reg: Register to read
unsigned int mask: Mask to use after shifting the register value
unsigned int shift: Right shift of register value
unsigned int sign_bit: Bit that describes if a number is negative or not.
int *signed_val: Pointer to where the read value should be stored

Description

This functions reads a codec register. The register value is shifted right by ‘shift’ bits and masked with the given ‘mask’. Afterwards it translates the given registervalue into a signed integer if sign_bit is non-zero.

Returns 0 on sucess, otherwise an error value

int snd_soc_info_volsw(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_info *uinfo)¶: single mixer info callback

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_info *uinfo: control element information

Description

Callback to provide information about a single mixer control, or a double mixer control that spans 2 registers.

Returns 0 for success.

int snd_soc_info_volsw_sx(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_info *uinfo)¶: Mixer info callback for SX TLV controls

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_info *uinfo: control element information

Description

Callback to provide information about a single mixer control, or a double mixer control that spans 2 registers of the SX TLV type. SX TLV controls have a range that represents both positive and negative values either side of zero but without a sign bit. min is the minimum register value, max is the number of steps.

Returns 0 for success.

int snd_soc_get_volsw(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: single mixer get callback

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback to get the value of a single mixer control, or a double mixer control that spans 2 registers.

Returns 0 for success.

int snd_soc_put_volsw(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: single mixer put callback

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback to set the value of a single mixer control, or a double mixer control that spans 2 registers.

Returns 0 for success.

int snd_soc_get_volsw_sx(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: single mixer get callback

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback to get the value of a single mixer control, or a double mixer control that spans 2 registers.

Returns 0 for success.

int snd_soc_put_volsw_sx(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: double mixer set callback

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback to set the value of a double mixer control that spans 2 registers.

Returns 0 for success.

int snd_soc_info_volsw_range(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_info *uinfo)¶: single mixer info callback with range.

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_info *uinfo: control element information

Description

Callback to provide information, within a range, about a single mixer control.

returns 0 for success.

int snd_soc_put_volsw_range(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: single mixer put value callback with range.

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback to set the value, within a range, for a single mixer control.

Returns 0 for success.

int snd_soc_get_volsw_range(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: single mixer get callback with range

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback to get the value, within a range, of a single mixer control.

Returns 0 for success.

int snd_soc_limit_volume(struct snd_soc_card *card, const char *name, int max)¶: Set new limit to an existing volume control.

Parameters

struct snd_soc_card *card: where to look for the control
const char *name: Name of the control
int max: new maximum limit

Description

Return 0 for success, else error.

int snd_soc_info_xr_sx(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_info *uinfo)¶: signed multi register info callback

Parameters

struct snd_kcontrol *kcontrol: mreg control
struct snd_ctl_elem_info *uinfo: control element information

Description

Callback to provide information of a control that can span multiple codec registers which together forms a single signed value in a MSB/LSB manner.

Returns 0 for success.

int snd_soc_get_xr_sx(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: signed multi register get callback

Parameters

struct snd_kcontrol *kcontrol: mreg control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback to get the value of a control that can span multiple codec registers which together forms a single signed value in a MSB/LSB manner. The control supports specifying total no of bits used to allow for bitfields across the multiple codec registers.

Returns 0 for success.

int snd_soc_put_xr_sx(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: signed multi register get callback

Parameters

struct snd_kcontrol *kcontrol: mreg control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback to set the value of a control that can span multiple codec registers which together forms a single signed value in a MSB/LSB manner. The control supports specifying total no of bits used to allow for bitfields across the multiple codec registers.

Returns 0 for success.

int snd_soc_get_strobe(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: strobe get callback

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback get the value of a strobe mixer control.

Returns 0 for success.

int snd_soc_put_strobe(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: strobe put callback

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback strobe a register bit to high then low (or the inverse) in one pass of a single mixer enum control.

Returns 1 for success.

int snd_soc_new_compress(struct snd_soc_pcm_runtime *rtd, int num)¶: create a new compress.

Parameters

struct snd_soc_pcm_runtime *rtd: The runtime for which we will create compress
int num: the device index number (zero based - shared with normal PCMs)

Return

0 for success, else error.

ASoC DAPM API¶

struct snd_soc_dapm_widget *snd_soc_dapm_kcontrol_widget(struct snd_kcontrol *kcontrol)¶: Returns the widget associated to a kcontrol

Parameters

struct snd_kcontrol *kcontrol: The kcontrol

struct snd_soc_dapm_context *snd_soc_dapm_kcontrol_dapm(struct snd_kcontrol *kcontrol)¶: Returns the dapm context associated to a kcontrol

Parameters

struct snd_kcontrol *kcontrol: The kcontrol

Note

This function must only be used on kcontrols that are known to have been registered for a CODEC. Otherwise the behaviour is undefined.

int snd_soc_dapm_force_bias_level(struct snd_soc_dapm_context *dapm, enum snd_soc_bias_level level)¶: Sets the DAPM bias level

Parameters

struct snd_soc_dapm_context *dapm: The DAPM context for which to set the level
enum snd_soc_bias_level level: The level to set

Description

Forces the DAPM bias level to a specific state. It will call the bias level callback of DAPM context with the specified level. This will even happen if the context is already at the same level. Furthermore it will not go through the normal bias level sequencing, meaning any intermediate states between the current and the target state will not be entered.

Note that the change in bias level is only temporary and the next time snd_soc_dapm_sync() is called the state will be set to the level as determined by the DAPM core. The function is mainly intended to be used to used during probe or resume from suspend to power up the device so initialization can be done, before the DAPM core takes over.

int snd_soc_dapm_set_bias_level(struct snd_soc_dapm_context *dapm, enum snd_soc_bias_level level)¶: set the bias level for the system

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
enum snd_soc_bias_level level: level to configure

Description

Configure the bias (power) levels for the SoC audio device.

Returns 0 for success else error.

int snd_soc_dapm_dai_get_connected_widgets(struct snd_soc_dai *dai, int stream, struct snd_soc_dapm_widget_list **list, bool (*custom_stop_condition)(struct snd_soc_dapm_widget*, enum snd_soc_dapm_direction))¶: query audio path and it’s widgets.

Parameters

struct snd_soc_dai *dai: the soc DAI.
int stream: stream direction.
struct snd_soc_dapm_widget_list **list: list of active widgets for this stream.
bool (*custom_stop_condition)(struct snd_soc_dapm_widget *, enum snd_soc_dapm_direction): (optional) a function meant to stop the widget graph walk based on custom logic.

Description

Queries DAPM graph as to whether a valid audio stream path exists for the initial stream specified by name. This takes into account current mixer and mux kcontrol settings. Creates list of valid widgets.

Optionally, can be supplied with a function acting as a stopping condition. This function takes the dapm widget currently being examined and the walk direction as an arguments, it should return true if the walk should be stopped and false otherwise.

Returns the number of valid paths or negative error.

void snd_soc_dapm_free_widget(struct snd_soc_dapm_widget *w)¶: Free specified widget

Parameters

struct snd_soc_dapm_widget *w: widget to free

Description

Removes widget from all paths and frees memory occupied by it.

int snd_soc_dapm_sync_unlocked(struct snd_soc_dapm_context *dapm)¶: scan and power dapm paths

Parameters

struct snd_soc_dapm_context *dapm: DAPM context

Description

Walks all dapm audio paths and powers widgets according to their stream or path usage.

Requires external locking.

Returns 0 for success.

int snd_soc_dapm_sync(struct snd_soc_dapm_context *dapm)¶: scan and power dapm paths

Parameters

struct snd_soc_dapm_context *dapm: DAPM context

Description

Walks all dapm audio paths and powers widgets according to their stream or path usage.

Returns 0 for success.

int snd_soc_dapm_add_routes(struct snd_soc_dapm_context *dapm, const struct snd_soc_dapm_route *route, int num)¶: Add routes between DAPM widgets

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
const struct snd_soc_dapm_route *route: audio routes
int num: number of routes

Description

Connects 2 dapm widgets together via a named audio path. The sink is the widget receiving the audio signal, whilst the source is the sender of the audio signal.

Returns 0 for success else error. On error all resources can be freed with a call to snd_soc_card_free().

int snd_soc_dapm_del_routes(struct snd_soc_dapm_context *dapm, const struct snd_soc_dapm_route *route, int num)¶: Remove routes between DAPM widgets

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
const struct snd_soc_dapm_route *route: audio routes
int num: number of routes

Description

Removes routes from the DAPM context.

int snd_soc_dapm_weak_routes(struct snd_soc_dapm_context *dapm, const struct snd_soc_dapm_route *route, int num)¶: Mark routes between DAPM widgets as weak

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
const struct snd_soc_dapm_route *route: audio routes
int num: number of routes

Description

Mark existing routes matching those specified in the passed array as being weak, meaning that they are ignored for the purpose of power decisions. The main intended use case is for sidetone paths which couple audio between other independent paths if they are both active in order to make the combination work better at the user level but which aren’t intended to be “used”.

Note that CODEC drivers should not use this as sidetone type paths can frequently also be used as bypass paths.

int snd_soc_dapm_new_widgets(struct snd_soc_card *card)¶: add new dapm widgets

Parameters

struct snd_soc_card *card: card to be checked for new dapm widgets

Description

Checks the codec for any new dapm widgets and creates them if found.

Returns 0 for success.

int snd_soc_dapm_get_volsw(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: dapm mixer get callback

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback to get the value of a dapm mixer control.

Returns 0 for success.

int snd_soc_dapm_put_volsw(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: dapm mixer set callback

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback to set the value of a dapm mixer control.

Returns 0 for success.

int snd_soc_dapm_get_enum_double(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: dapm enumerated double mixer get callback

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback to get the value of a dapm enumerated double mixer control.

Returns 0 for success.

int snd_soc_dapm_put_enum_double(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: dapm enumerated double mixer set callback

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: control element information

Description

Callback to set the value of a dapm enumerated double mixer control.

Returns 0 for success.

int snd_soc_dapm_info_pin_switch(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_info *uinfo)¶: Info for a pin switch

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_info *uinfo: control element information

Description

Callback to provide information about a pin switch control.

int snd_soc_dapm_get_pin_switch(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: Get information for a pin switch

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: Value

int snd_soc_dapm_put_pin_switch(struct snd_kcontrol *kcontrol, struct snd_ctl_elem_value *ucontrol)¶: Set information for a pin switch

Parameters

struct snd_kcontrol *kcontrol: mixer control
struct snd_ctl_elem_value *ucontrol: Value

struct snd_soc_dapm_widget *snd_soc_dapm_new_control(struct snd_soc_dapm_context *dapm, const struct snd_soc_dapm_widget *widget)¶: create new dapm control

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
const struct snd_soc_dapm_widget *widget: widget template

Description

Creates new DAPM control based upon a template.

Returns a widget pointer on success or an error pointer on failure

int snd_soc_dapm_new_controls(struct snd_soc_dapm_context *dapm, const struct snd_soc_dapm_widget *widget, unsigned int num)¶: create new dapm controls

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
const struct snd_soc_dapm_widget *widget: widget array
unsigned int num: number of widgets

Description

Creates new DAPM controls based upon the templates.

Returns 0 for success else error.

int snd_soc_dapm_new_dai_widgets(struct snd_soc_dapm_context *dapm, struct snd_soc_dai *dai)¶: Create new DAPM widgets

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
struct snd_soc_dai *dai: parent DAI

Description

Returns 0 on success, error code otherwise.

void snd_soc_dapm_stream_event(struct snd_soc_pcm_runtime *rtd, int stream, int event)¶: send a stream event to the dapm core

Parameters

struct snd_soc_pcm_runtime *rtd: PCM runtime data
int stream: stream name
int event: stream event

Description

Sends a stream event to the dapm core. The core then makes any necessary widget power changes.

Returns 0 for success else error.

int snd_soc_dapm_enable_pin_unlocked(struct snd_soc_dapm_context *dapm, const char *pin)¶: enable pin.

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
const char *pin: pin name

Description

Enables input/output pin and its parents or children widgets iff there is a valid audio route and active audio stream.

Requires external locking.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_enable_pin(struct snd_soc_dapm_context *dapm, const char *pin)¶: enable pin.

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
const char *pin: pin name

Description

Enables input/output pin and its parents or children widgets iff there is a valid audio route and active audio stream.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_force_enable_pin_unlocked(struct snd_soc_dapm_context *dapm, const char *pin)¶: force a pin to be enabled

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
const char *pin: pin name

Description

Enables input/output pin regardless of any other state. This is intended for use with microphone bias supplies used in microphone jack detection.

Requires external locking.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_force_enable_pin(struct snd_soc_dapm_context *dapm, const char *pin)¶: force a pin to be enabled

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
const char *pin: pin name

Description

Enables input/output pin regardless of any other state. This is intended for use with microphone bias supplies used in microphone jack detection.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_disable_pin_unlocked(struct snd_soc_dapm_context *dapm, const char *pin)¶: disable pin.

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
const char *pin: pin name

Description

Disables input/output pin and its parents or children widgets.

Requires external locking.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_disable_pin(struct snd_soc_dapm_context *dapm, const char *pin)¶: disable pin.

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
const char *pin: pin name

Description

Disables input/output pin and its parents or children widgets.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_nc_pin_unlocked(struct snd_soc_dapm_context *dapm, const char *pin)¶: permanently disable pin.

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
const char *pin: pin name

Description

Marks the specified pin as being not connected, disabling it along any parent or child widgets. At present this is identical to snd_soc_dapm_disable_pin() but in future it will be extended to do additional things such as disabling controls which only affect paths through the pin.

Requires external locking.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_nc_pin(struct snd_soc_dapm_context *dapm, const char *pin)¶: permanently disable pin.

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
const char *pin: pin name

Description

Marks the specified pin as being not connected, disabling it along any parent or child widgets. At present this is identical to snd_soc_dapm_disable_pin() but in future it will be extended to do additional things such as disabling controls which only affect paths through the pin.

NOTE

snd_soc_dapm_sync() needs to be called after this for DAPM to do any widget power switching.

int snd_soc_dapm_get_pin_status(struct snd_soc_dapm_context *dapm, const char *pin)¶: get audio pin status

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
const char *pin: audio signal pin endpoint (or start point)

Description

Get audio pin status - connected or disconnected.

Returns 1 for connected otherwise 0.

int snd_soc_dapm_ignore_suspend(struct snd_soc_dapm_context *dapm, const char *pin)¶: ignore suspend status for DAPM endpoint

Parameters

struct snd_soc_dapm_context *dapm: DAPM context
const char *pin: audio signal pin endpoint (or start point)

Description

Mark the given endpoint or pin as ignoring suspend. When the system is disabled a path between two endpoints flagged as ignoring suspend will not be disabled. The path must already be enabled via normal means at suspend time, it will not be turned on if it was not already enabled.

void snd_soc_dapm_free(struct snd_soc_dapm_context *dapm)¶: free dapm resources

Parameters

struct snd_soc_dapm_context *dapm: DAPM context

Description

Free all dapm widgets and resources.

ASoC DMA Engine API¶

int snd_dmaengine_pcm_prepare_slave_config(struct snd_pcm_substream *substream, struct snd_pcm_hw_params *params, struct dma_slave_config *slave_config)¶: Generic prepare_slave_config callback

Parameters

struct snd_pcm_substream *substream: PCM substream
struct snd_pcm_hw_params *params: hw_params
struct dma_slave_config *slave_config: DMA slave config to prepare

Description

This function can be used as a generic prepare_slave_config callback for platforms which make use of the snd_dmaengine_dai_dma_data struct for their DAI DMA data. Internally the function will first call snd_hwparams_to_dma_slave_config to fill in the slave config based on the hw_params, followed by snd_dmaengine_pcm_set_config_from_dai_data to fill in the remaining fields based on the DAI DMA data.

int snd_dmaengine_pcm_register(struct device *dev, const struct snd_dmaengine_pcm_config *config, unsigned int flags)¶: Register a dmaengine based PCM device

Parameters

struct device *dev: The parent device for the PCM device
const struct snd_dmaengine_pcm_config *config: Platform specific PCM configuration
unsigned int flags: Platform specific quirks

void snd_dmaengine_pcm_unregister(struct device *dev)¶: Removes a dmaengine based PCM device

Parameters

struct device *dev: Parent device the PCM was register with

Description

Removes a dmaengine based PCM device previously registered with snd_dmaengine_pcm_register.

Miscellaneous Functions¶

Hardware-Dependent Devices API¶

int snd_hwdep_new(struct snd_card *card, char *id, int device, struct snd_hwdep **rhwdep)¶: create a new hwdep instance

Parameters

struct snd_card *card: the card instance
char *id: the id string
int device: the device index (zero-based)
struct snd_hwdep **rhwdep: the pointer to store the new hwdep instance

Description

Creates a new hwdep instance with the given index on the card. The callbacks (hwdep->ops) must be set on the returned instance after this call manually by the caller.

Return

Zero if successful, or a negative error code on failure.

Jack Abstraction Layer API¶

enum snd_jack_types¶: Jack types which can be reported

Constants

SND_JACK_HEADPHONE: Headphone
SND_JACK_MICROPHONE: Microphone
SND_JACK_HEADSET: Headset
SND_JACK_LINEOUT: Line out
SND_JACK_MECHANICAL: Mechanical switch
SND_JACK_VIDEOOUT: Video out
SND_JACK_AVOUT: AV (Audio Video) out
SND_JACK_LINEIN: Line in
SND_JACK_BTN_0: Button 0
SND_JACK_BTN_1: Button 1
SND_JACK_BTN_2: Button 2
SND_JACK_BTN_3: Button 3
SND_JACK_BTN_4: Button 4
SND_JACK_BTN_5: Button 5

Description

These values are used as a bitmask.

Note that this must be kept in sync with the lookup table in sound/core/jack.c.

int snd_jack_add_new_kctl(struct snd_jack *jack, const char *name, int mask)¶: Create a new snd_jack_kctl and add it to jack

Parameters

struct snd_jack *jack: the jack instance which the kctl will attaching to
const char * name: the name for the snd_kcontrol object
int mask: a bitmask of enum snd_jack_type values that can be detected by this snd_jack_kctl object.

Description

Creates a new snd_kcontrol object and adds it to the jack kctl_list.

Return

Zero if successful, or a negative error code on failure.

int snd_jack_new(struct snd_card *card, const char *id, int type, struct snd_jack **jjack, bool initial_kctl, bool phantom_jack)¶: Create a new jack

Parameters

struct snd_card *card: the card instance
const char *id: an identifying string for this jack
int type: a bitmask of enum snd_jack_type values that can be detected by this jack
struct snd_jack **jjack: Used to provide the allocated jack object to the caller.
bool initial_kctl: if true, create a kcontrol and add it to the jack list.
bool phantom_jack: Don’t create a input device for phantom jacks.

Description

Creates a new jack object.

Return

Zero if successful, or a negative error code on failure. On success jjack will be initialised.

void snd_jack_set_parent(struct snd_jack *jack, struct device *parent)¶: Set the parent device for a jack

Parameters

struct snd_jack *jack: The jack to configure
struct device *parent: The device to set as parent for the jack.

Description

Set the parent for the jack devices in the device tree. This function is only valid prior to registration of the jack. If no parent is configured then the parent device will be the sound card.

int snd_jack_set_key(struct snd_jack *jack, enum snd_jack_types type, int keytype)¶: Set a key mapping on a jack

Parameters

struct snd_jack *jack: The jack to configure
enum snd_jack_types type: Jack report type for this key
int keytype: Input layer key type to be reported

Description

Map a SND_JACK_BTN_* button type to an input layer key, allowing reporting of keys on accessories via the jack abstraction. If no mapping is provided but keys are enabled in the jack type then BTN_n numeric buttons will be reported.

If jacks are not reporting via the input API this call will have no effect.

Note that this is intended to be use by simple devices with small numbers of keys that can be reported. It is also possible to access the input device directly - devices with complex input capabilities on accessories should consider doing this rather than using this abstraction.

This function may only be called prior to registration of the jack.

Return

Zero if successful, or a negative error code on failure.

void snd_jack_report(struct snd_jack *jack, int status)¶: Report the current status of a jack

Parameters

struct snd_jack *jack: The jack to report status for
int status: The current status of the jack

Note

This function uses mutexes and should be called from a context which can sleep (such as a workqueue).

void snd_soc_jack_report(struct snd_soc_jack *jack, int status, int mask)¶: Report the current status for a jack

Parameters

struct snd_soc_jack *jack: the jack
int status: a bitmask of enum snd_jack_type values that are currently detected.
int mask: a bitmask of enum snd_jack_type values that being reported.

Description

If configured using snd_soc_jack_add_pins() then the associated DAPM pins will be enabled or disabled as appropriate and DAPM synchronised.

Note

This function uses mutexes and should be called from a context which can sleep (such as a workqueue).

int snd_soc_jack_add_zones(struct snd_soc_jack *jack, int count, struct snd_soc_jack_zone *zones)¶: Associate voltage zones with jack

Parameters

struct snd_soc_jack *jack: ASoC jack
int count: Number of zones
struct snd_soc_jack_zone *zones: Array of zones

Description

After this function has been called the zones specified in the array will be associated with the jack.

int snd_soc_jack_get_type(struct snd_soc_jack *jack, int micbias_voltage)¶: Based on the mic bias value, this function returns the type of jack from the zones declared in the jack type

Parameters

struct snd_soc_jack *jack: ASoC jack
int micbias_voltage: mic bias voltage at adc channel when jack is plugged in

Description

Based on the mic bias value passed, this function helps identify the type of jack from the already declared jack zones

int snd_soc_jack_add_pins(struct snd_soc_jack *jack, int count, struct snd_soc_jack_pin *pins)¶: Associate DAPM pins with an ASoC jack

Parameters

struct snd_soc_jack *jack: ASoC jack created with snd_soc_card_jack_new_pins()
int count: Number of pins
struct snd_soc_jack_pin *pins: Array of pins

Description

After this function has been called the DAPM pins specified in the pins array will have their status updated to reflect the current state of the jack whenever the jack status is updated.

void snd_soc_jack_notifier_register(struct snd_soc_jack *jack, struct notifier_block *nb)¶: Register a notifier for jack status

Parameters

struct snd_soc_jack *jack: ASoC jack
struct notifier_block *nb: Notifier block to register

Description

Register for notification of the current status of the jack. Note that it is not possible to report additional jack events in the callback from the notifier, this is intended to support applications such as enabling electrical detection only when a mechanical detection event has occurred.

void snd_soc_jack_notifier_unregister(struct snd_soc_jack *jack, struct notifier_block *nb)¶: Unregister a notifier for jack status

Parameters

struct snd_soc_jack *jack: ASoC jack
struct notifier_block *nb: Notifier block to unregister

Description

Stop notifying for status changes.

int snd_soc_jack_add_gpios(struct snd_soc_jack *jack, int count, struct snd_soc_jack_gpio *gpios)¶: Associate GPIO pins with an ASoC jack

Parameters

struct snd_soc_jack *jack: ASoC jack
int count: number of pins
struct snd_soc_jack_gpio *gpios: array of gpio pins

Description

This function will request gpio, set data direction and request irq for each gpio in the array.

int snd_soc_jack_add_gpiods(struct device *gpiod_dev, struct snd_soc_jack *jack, int count, struct snd_soc_jack_gpio *gpios)¶: Associate GPIO descriptor pins with an ASoC jack

Parameters

struct device *gpiod_dev: GPIO consumer device
struct snd_soc_jack *jack: ASoC jack
int count: number of pins
struct snd_soc_jack_gpio *gpios: array of gpio pins

Description

This function will request gpio, set data direction and request irq for each gpio in the array.

void snd_soc_jack_free_gpios(struct snd_soc_jack *jack, int count, struct snd_soc_jack_gpio *gpios)¶: Release GPIO pins’ resources of an ASoC jack

Parameters

struct snd_soc_jack *jack: ASoC jack
int count: number of pins
struct snd_soc_jack_gpio *gpios: array of gpio pins

Description

Release gpio and irq resources for gpio pins associated with an ASoC jack.

ISA DMA Helpers¶

void snd_dma_program(unsigned long dma, unsigned long addr, unsigned int size, unsigned short mode)¶: program an ISA DMA transfer

Parameters

unsigned long dma: the dma number
unsigned long addr: the physical address of the buffer
unsigned int size: the DMA transfer size
unsigned short mode: the DMA transfer mode, DMA_MODE_XXX

Description

Programs an ISA DMA transfer for the given buffer.

void snd_dma_disable(unsigned long dma)¶: stop the ISA DMA transfer

Parameters

unsigned long dma: the dma number

Description

Stops the ISA DMA transfer.

unsigned int snd_dma_pointer(unsigned long dma, unsigned int size)¶: return the current pointer to DMA transfer buffer in bytes

Parameters

unsigned long dma: the dma number
unsigned int size: the dma transfer size

Return

The current pointer in DMA transfer buffer in bytes.

int snd_devm_request_dma(struct device *dev, int dma, const char *name)¶: the managed version of request_dma()

Parameters

struct device *dev: the device pointer
int dma: the dma number
const char *name: the name string of the requester

Description

The requested DMA will be automatically released at unbinding via devres.

Return

zero on success, or a negative error code

Other Helper Macros¶

void snd_power_ref(struct snd_card *card)¶: Take the reference count for power control

Parameters

struct snd_card *card: sound card object

Description

The power_ref reference of the card is used for managing to block the snd_power_sync_ref() operation. This function increments the reference. The counterpart snd_power_unref() has to be called appropriately later.

void snd_power_unref(struct snd_card *card)¶: Release the reference count for power control

Parameters

struct snd_card *card: sound card object

void snd_power_sync_ref(struct snd_card *card)¶: wait until the card power_ref is freed

Parameters

struct snd_card *card: sound card object

Description

This function is used to synchronize with the pending power_ref being released.

void snd_card_unref(struct snd_card *card)¶: Unreference the card object

Parameters

struct snd_card *card: the card object to unreference

Description

Call this function for the card object that was obtained via snd_card_ref() or snd_lookup_minor_data().

snd_printk¶

snd_printk (fmt, ...)

printk wrapper

Parameters

fmt: format string
...: variable arguments

Description

Works like printk() but prints the file and the line of the caller when configured with CONFIG_SND_VERBOSE_PRINTK.

snd_printd¶

snd_printd (fmt, ...)

debug printk

Parameters

fmt: format string
...: variable arguments

Description

Works like snd_printk() for debugging purposes. Ignored when CONFIG_SND_DEBUG is not set.

snd_BUG¶

snd_BUG ()

give a BUG warning message and stack trace

Parameters

Description

Calls WARN() if CONFIG_SND_DEBUG is set. Ignored when CONFIG_SND_DEBUG is not set.

snd_printd_ratelimit¶

snd_printd_ratelimit ()

Suppress high rates of output when CONFIG_SND_DEBUG is enabled.

Parameters

snd_BUG_ON¶

snd_BUG_ON (cond)

debugging check macro

Parameters

cond: condition to evaluate

Description

Has the same behavior as WARN_ON when CONFIG_SND_DEBUG is set, otherwise just evaluates the conditional and returns the value.

snd_printdd¶

snd_printdd (format, ...)

debug printk

Parameters

format: format string
...: variable arguments

Description

Works like snd_printk() for debugging purposes. Ignored when CONFIG_SND_DEBUG_VERBOSE is not set.

int register_sound_special_device(const struct file_operations *fops, int unit, struct device *dev)¶: register a special sound node

Parameters

const struct file_operations *fops

File operations for the driver

int unit

Unit number to allocate

struct device *dev

device pointer

Allocate a special sound device by minor number from the sound subsystem.

Return

The allocated number is returned on success. On failure,: a negative error code is returned.

int register_sound_mixer(const struct file_operations *fops, int dev)¶: register a mixer device

Parameters

const struct file_operations *fops

File operations for the driver

int dev

Unit number to allocate

Allocate a mixer device. Unit is the number of the mixer requested. Pass -1 to request the next free mixer unit.

Return

On success, the allocated number is returned. On failure,: a negative error code is returned.

int register_sound_dsp(const struct file_operations *fops, int dev)¶: register a DSP device

Parameters

const struct file_operations *fops

File operations for the driver

int dev

Unit number to allocate

Allocate a DSP device. Unit is the number of the DSP requested. Pass -1 to request the next free DSP unit.

This function allocates both the audio and dsp device entries together and will always allocate them as a matching pair - eg dsp3/audio3

Return

On success, the allocated number is returned. On failure,: a negative error code is returned.

void unregister_sound_special(int unit)¶: unregister a special sound device

Parameters

int unit

unit number to allocate

Release a sound device that was allocated with register_sound_special(). The unit passed is the return value from the register function.

void unregister_sound_mixer(int unit)¶: unregister a mixer

Parameters

int unit

unit number to allocate

Release a sound device that was allocated with register_sound_mixer(). The unit passed is the return value from the register function.

void unregister_sound_dsp(int unit)¶: unregister a DSP device

Parameters

int unit

unit number to allocate

Release a sound device that was allocated with register_sound_dsp(). The unit passed is the return value from the register function.

Both of the allocated units are released together automatically.

The Linux Kernel

Contents

This Page

The ALSA Driver API¶

Management of Cards and Devices¶

Card Management¶

Device Components¶

Module requests and Device File Entries¶

Memory Management Helpers¶

PCM API¶

PCM Core¶

PCM Format Helpers¶

PCM Memory Management¶

PCM DMA Engine API¶

Control/Mixer API¶

General Control Interface¶

AC97 Codec API¶

Virtual Master Control API¶

MIDI API¶

Raw MIDI API¶

MPU401-UART API¶

Proc Info API¶

Proc Info Interface¶

Compress Offload¶

Compress Offload API¶

ASoC¶

ASoC Core API¶

ASoC DAPM API¶

ASoC DMA Engine API¶

Miscellaneous Functions¶

Hardware-Dependent Devices API¶

Jack Abstraction Layer API¶

ISA DMA Helpers¶

Other Helper Macros¶