2.7. V4L2 sub-devices¶

Many drivers need to communicate with sub-devices. These devices can do all sort of tasks, but most commonly they handle audio and/or video muxing, encoding or decoding. For webcams common sub-devices are sensors and camera controllers.

Usually these are I2C devices, but not necessarily. In order to provide the driver with a consistent interface to these sub-devices the v4l2_subdev struct (v4l2-subdev.h) was created.

Each sub-device driver must have a v4l2_subdev struct. This struct can be stand-alone for simple sub-devices or it might be embedded in a larger struct if more state information needs to be stored. Usually there is a low-level device struct (e.g. i2c_client) that contains the device data as setup by the kernel. It is recommended to store that pointer in the private data of v4l2_subdev using v4l2_set_subdevdata(). That makes it easy to go from a v4l2_subdev to the actual low-level bus-specific device data.

You also need a way to go from the low-level struct to v4l2_subdev. For the common i2c_client struct the i2c_set_clientdata() call is used to store a v4l2_subdev pointer, for other buses you may have to use other methods.

Bridges might also need to store per-subdev private data, such as a pointer to bridge-specific per-subdev private data. The v4l2_subdev structure provides host private data for that purpose that can be accessed with v4l2_get_subdev_hostdata() and v4l2_set_subdev_hostdata().

From the bridge driver perspective, you load the sub-device module and somehow obtain the v4l2_subdev pointer. For i2c devices this is easy: you call i2c_get_clientdata(). For other buses something similar needs to be done. Helper functions exist for sub-devices on an I2C bus that do most of this tricky work for you.

Each v4l2_subdev contains function pointers that sub-device drivers can implement (or leave NULL if it is not applicable). Since sub-devices can do so many different things and you do not want to end up with a huge ops struct of which only a handful of ops are commonly implemented, the function pointers are sorted according to category and each category has its own ops struct.

The top-level ops struct contains pointers to the category ops structs, which may be NULL if the subdev driver does not support anything from that category.

It looks like this:

struct v4l2_subdev_core_ops {
        int (*log_status)(struct v4l2_subdev *sd);
        int (*init)(struct v4l2_subdev *sd, u32 val);
        ...
};

struct v4l2_subdev_tuner_ops {
        ...
};

struct v4l2_subdev_audio_ops {
        ...
};

struct v4l2_subdev_video_ops {
        ...
};

struct v4l2_subdev_pad_ops {
        ...
};

struct v4l2_subdev_ops {
        const struct v4l2_subdev_core_ops  *core;
        const struct v4l2_subdev_tuner_ops *tuner;
        const struct v4l2_subdev_audio_ops *audio;
        const struct v4l2_subdev_video_ops *video;
        const struct v4l2_subdev_pad_ops *video;
};

The core ops are common to all subdevs, the other categories are implemented depending on the sub-device. E.g. a video device is unlikely to support the audio ops and vice versa.

This setup limits the number of function pointers while still making it easy to add new ops and categories.

A sub-device driver initializes the v4l2_subdev struct using:

v4l2_subdev_init (sd, &ops).

Afterwards you need to initialize sd->name with a unique name and set the module owner. This is done for you if you use the i2c helper functions.

If integration with the media framework is needed, you must initialize the media_entity struct embedded in the v4l2_subdev struct (entity field) by calling media_entity_pads_init(), if the entity has pads:

struct media_pad *pads = &my_sd->pads;
int err;

err = media_entity_pads_init(&sd->entity, npads, pads);

The pads array must have been previously initialized. There is no need to manually set the struct media_entity function and name fields, but the revision field must be initialized if needed.

A reference to the entity will be automatically acquired/released when the subdev device node (if any) is opened/closed.

Don’t forget to cleanup the media entity before the sub-device is destroyed:

media_entity_cleanup(&sd->entity);

If a sub-device driver implements sink pads, the subdev driver may set the link_validate field in v4l2_subdev_pad_ops to provide its own link validation function. For every link in the pipeline, the link_validate pad operation of the sink end of the link is called. In both cases the driver is still responsible for validating the correctness of the format configuration between sub-devices and video nodes.

If link_validate op is not set, the default function v4l2_subdev_link_validate_default() is used instead. This function ensures that width, height and the media bus pixel code are equal on both source and sink of the link. Subdev drivers are also free to use this function to perform the checks mentioned above in addition to their own checks.

2.7.1. Subdev registration¶

There are currently two ways to register subdevices with the V4L2 core. The first (traditional) possibility is to have subdevices registered by bridge drivers. This can be done when the bridge driver has the complete information about subdevices connected to it and knows exactly when to register them. This is typically the case for internal subdevices, like video data processing units within SoCs or complex PCI(e) boards, camera sensors in USB cameras or connected to SoCs, which pass information about them to bridge drivers, usually in their platform data.

There are however also situations where subdevices have to be registered asynchronously to bridge devices. An example of such a configuration is a Device Tree based system where information about subdevices is made available to the system independently from the bridge devices, e.g. when subdevices are defined in DT as I2C device nodes. The API used in this second case is described further below.

Using one or the other registration method only affects the probing process, the run-time bridge-subdevice interaction is in both cases the same.

2.7.1.1. Registering synchronous sub-devices¶

In the synchronous case a device (bridge) driver needs to register the v4l2_subdev with the v4l2_device:

v4l2_device_register_subdev (v4l2_dev, sd).

This can fail if the subdev module disappeared before it could be registered. After this function was called successfully the subdev->dev field points to the v4l2_device.

If the v4l2_device parent device has a non-NULL mdev field, the sub-device entity will be automatically registered with the media device.

You can unregister a sub-device using:

v4l2_device_unregister_subdev (sd).

Afterwards the subdev module can be unloaded and sd->dev == NULL.

2.7.1.2. Registering asynchronous sub-devices¶

In the asynchronous case subdevice probing can be invoked independently of the bridge driver availability. The subdevice driver then has to verify whether all the requirements for a successful probing are satisfied. This can include a check for a master clock availability. If any of the conditions aren’t satisfied the driver might decide to return -EPROBE_DEFER to request further reprobing attempts. Once all conditions are met the subdevice shall be registered using the v4l2_async_register_subdev() function. Unregistration is performed using the v4l2_async_unregister_subdev() call. Subdevices registered this way are stored in a global list of subdevices, ready to be picked up by bridge drivers.

Drivers must complete all initialization of the sub-device before registering it using v4l2_async_register_subdev(), including enabling runtime PM. This is because the sub-device becomes accessible as soon as it gets registered.

2.7.1.3. Asynchronous sub-device notifiers¶

Bridge drivers in turn have to register a notifier object. This is performed using the v4l2_async_nf_register() call. To unregister the notifier the driver has to call v4l2_async_nf_unregister(). Before releasing memory of an unregister notifier, it must be cleaned up by calling v4l2_async_nf_cleanup().

Before registering the notifier, bridge drivers must do two things: first, the notifier must be initialized using the v4l2_async_nf_init(). Second, bridge drivers can then begin to form a list of async connection descriptors that the bridge device needs for its operation. v4l2_async_nf_add_fwnode(), v4l2_async_nf_add_fwnode_remote() and v4l2_async_nf_add_i2c()

Async connection descriptors describe connections to external sub-devices the drivers for which are not yet probed. Based on an async connection, a media data or ancillary link may be created when the related sub-device becomes available. There may be one or more async connections to a given sub-device but this is not known at the time of adding the connections to the notifier. Async connections are bound as matching async sub-devices are found, one by one.

2.7.1.4. Asynchronous sub-device notifier for sub-devices¶

A driver that registers an asynchronous sub-device may also register an asynchronous notifier. This is called an asynchronous sub-device notifier and the process is similar to that of a bridge driver apart from that the notifier is initialised using v4l2_async_subdev_nf_init() instead. A sub-device notifier may complete only after the V4L2 device becomes available, i.e. there’s a path via async sub-devices and notifiers to a notifier that is not an asynchronous sub-device notifier.

2.7.1.5. Asynchronous sub-device registration helper for camera sensor drivers¶

v4l2_async_register_subdev_sensor() is a helper function for sensor drivers registering their own async connection, but it also registers a notifier and further registers async connections for lens and flash devices found in firmware. The notifier for the sub-device is unregistered and cleaned up with the async sub-device, using v4l2_async_unregister_subdev().

2.7.1.6. Asynchronous sub-device notifier example¶

These functions allocate an async connection descriptor which is of type struct v4l2_async_connection embedded in a driver-specific struct. The &struct v4l2_async_connection shall be the first member of this struct:

struct my_async_connection {
        struct v4l2_async_connection asc;
        ...
};

struct my_async_connection *my_asc;
struct fwnode_handle *ep;

...

my_asc = v4l2_async_nf_add_fwnode_remote(&notifier, ep,
                                         struct my_async_connection);
fwnode_handle_put(ep);

if (IS_ERR(my_asc))
        return PTR_ERR(my_asc);

2.7.1.7. Asynchronous sub-device notifier callbacks¶

The V4L2 core will then use these connection descriptors to match asynchronously registered subdevices to them. If a match is detected the .bound() notifier callback is called. After all connections have been bound the .complete() callback is called. When a connection is removed from the system the .unbind() method is called. All three callbacks are optional.

Drivers can store any type of custom data in their driver-specific v4l2_async_connection wrapper. If any of that data requires special handling when the structure is freed, drivers must implement the .destroy() notifier callback. The framework will call it right before freeing the v4l2_async_connection.

2.7.2. Calling subdev operations¶

The advantage of using v4l2_subdev is that it is a generic struct and does not contain any knowledge about the underlying hardware. So a driver might contain several subdevs that use an I2C bus, but also a subdev that is controlled through GPIO pins. This distinction is only relevant when setting up the device, but once the subdev is registered it is completely transparent.

Once the subdev has been registered you can call an ops function either directly:

err = sd->ops->core->g_std(sd, &norm);

but it is better and easier to use this macro:

err = v4l2_subdev_call(sd, core, g_std, &norm);

The macro will do the right NULL pointer checks and returns -ENODEV if sd is NULL, -ENOIOCTLCMD if either sd->core or sd->core->g_std is NULL, or the actual result of the sd->ops->core->g_std ops.

It is also possible to call all or a subset of the sub-devices:

v4l2_device_call_all(v4l2_dev, 0, core, g_std, &norm);

Any subdev that does not support this ops is skipped and error results are ignored. If you want to check for errors use this:

err = v4l2_device_call_until_err(v4l2_dev, 0, core, g_std, &norm);

Any error except -ENOIOCTLCMD will exit the loop with that error. If no errors (except -ENOIOCTLCMD) occurred, then 0 is returned.

The second argument to both calls is a group ID. If 0, then all subdevs are called. If non-zero, then only those whose group ID match that value will be called. Before a bridge driver registers a subdev it can set sd->grp_id to whatever value it wants (it’s 0 by default). This value is owned by the bridge driver and the sub-device driver will never modify or use it.

The group ID gives the bridge driver more control how callbacks are called. For example, there may be multiple audio chips on a board, each capable of changing the volume. But usually only one will actually be used when the user want to change the volume. You can set the group ID for that subdev to e.g. AUDIO_CONTROLLER and specify that as the group ID value when calling v4l2_device_call_all(). That ensures that it will only go to the subdev that needs it.

If the sub-device needs to notify its v4l2_device parent of an event, then it can call v4l2_subdev_notify(sd, notification, arg). This macro checks whether there is a notify() callback defined and returns -ENODEV if not. Otherwise the result of the notify() call is returned.

2.8. V4L2 sub-device userspace API¶

Bridge drivers traditionally expose one or multiple video nodes to userspace, and control subdevices through the v4l2_subdev_ops operations in response to video node operations. This hides the complexity of the underlying hardware from applications. For complex devices, finer-grained control of the device than what the video nodes offer may be required. In those cases, bridge drivers that implement the media controller API may opt for making the subdevice operations directly accessible from userspace.

Device nodes named v4l-subdevX can be created in /dev to access sub-devices directly. If a sub-device supports direct userspace configuration it must set the V4L2_SUBDEV_FL_HAS_DEVNODE flag before being registered.

After registering sub-devices, the v4l2_device driver can create device nodes for all registered sub-devices marked with V4L2_SUBDEV_FL_HAS_DEVNODE by calling v4l2_device_register_subdev_nodes(). Those device nodes will be automatically removed when sub-devices are unregistered.

The device node handles a subset of the V4L2 API.

VIDIOC_QUERYCTRL, VIDIOC_QUERYMENU, VIDIOC_G_CTRL, VIDIOC_S_CTRL, VIDIOC_G_EXT_CTRLS, VIDIOC_S_EXT_CTRLS and VIDIOC_TRY_EXT_CTRLS:

The controls ioctls are identical to the ones defined in V4L2. They behave identically, with the only exception that they deal only with controls implemented in the sub-device. Depending on the driver, those controls can be also be accessed through one (or several) V4L2 device nodes.

VIDIOC_DQEVENT, VIDIOC_SUBSCRIBE_EVENT and VIDIOC_UNSUBSCRIBE_EVENT

The events ioctls are identical to the ones defined in V4L2. They behave identically, with the only exception that they deal only with events generated by the sub-device. Depending on the driver, those events can also be reported by one (or several) V4L2 device nodes.

Sub-device drivers that want to use events need to set the V4L2_SUBDEV_FL_HAS_EVENTS v4l2_subdev.flags before registering the sub-device. After registration events can be queued as usual on the v4l2_subdev.devnode device node.

To properly support events, the poll() file operation is also implemented.

Private ioctls

All ioctls not in the above list are passed directly to the sub-device driver through the core::ioctl operation.

2.9. Read-only sub-device userspace API¶

Bridge drivers that control their connected subdevices through direct calls to the kernel API realized by v4l2_subdev_ops structure do not usually want userspace to be able to change the same parameters through the subdevice device node and thus do not usually register any.

It is sometimes useful to report to userspace the current subdevice configuration through a read-only API, that does not permit applications to change to the device parameters but allows interfacing to the subdevice device node to inspect them.

For instance, to implement cameras based on computational photography, userspace needs to know the detailed camera sensor configuration (in terms of skipping, binning, cropping and scaling) for each supported output resolution. To support such use cases, bridge drivers may expose the subdevice operations to userspace through a read-only API.

To create a read-only device node for all the subdevices registered with the V4L2_SUBDEV_FL_HAS_DEVNODE set, the v4l2_device driver should call v4l2_device_register_ro_subdev_nodes().

Access to the following ioctls for userspace applications is restricted on sub-device device nodes registered with v4l2_device_register_ro_subdev_nodes().

VIDIOC_SUBDEV_S_FMT, VIDIOC_SUBDEV_S_CROP, VIDIOC_SUBDEV_S_SELECTION:

These ioctls are only allowed on a read-only subdevice device node for the V4L2_SUBDEV_FORMAT_TRY formats and selection rectangles.

VIDIOC_SUBDEV_S_FRAME_INTERVAL, VIDIOC_SUBDEV_S_DV_TIMINGS, VIDIOC_SUBDEV_S_STD:

These ioctls are not allowed on a read-only subdevice node.

In case the ioctl is not allowed, or the format to modify is set to V4L2_SUBDEV_FORMAT_ACTIVE, the core returns a negative error code and the errno variable is set to -EPERM.

2.10. I2C sub-device drivers¶

Since these drivers are so common, special helper functions are available to ease the use of these drivers (v4l2-common.h).

The recommended method of adding v4l2_subdev support to an I2C driver is to embed the v4l2_subdev struct into the state struct that is created for each I2C device instance. Very simple devices have no state struct and in that case you can just create a v4l2_subdev directly.

A typical state struct would look like this (where ‘chipname’ is replaced by the name of the chip):

struct chipname_state {
        struct v4l2_subdev sd;
        ...  /* additional state fields */
};

Initialize the v4l2_subdev struct as follows:

v4l2_i2c_subdev_init(&state->sd, client, subdev_ops);

This function will fill in all the fields of v4l2_subdev ensure that the v4l2_subdev and i2c_client both point to one another.

You should also add a helper inline function to go from a v4l2_subdev pointer to a chipname_state struct:

static inline struct chipname_state *to_state(struct v4l2_subdev *sd)
{
        return container_of(sd, struct chipname_state, sd);
}

Use this to go from the v4l2_subdev struct to the i2c_client struct:

struct i2c_client *client = v4l2_get_subdevdata(sd);

And this to go from an i2c_client to a v4l2_subdev struct:

struct v4l2_subdev *sd = i2c_get_clientdata(client);

Make sure to call v4l2_device_unregister_subdev()(sd) when the remove() callback is called. This will unregister the sub-device from the bridge driver. It is safe to call this even if the sub-device was never registered.

You need to do this because when the bridge driver destroys the i2c adapter the remove() callbacks are called of the i2c devices on that adapter. After that the corresponding v4l2_subdev structures are invalid, so they have to be unregistered first. Calling v4l2_device_unregister_subdev()(sd) from the remove() callback ensures that this is always done correctly.

The bridge driver also has some helper functions it can use:

struct v4l2_subdev *sd = v4l2_i2c_new_subdev(v4l2_dev, adapter,
                                "module_foo", "chipid", 0x36, NULL);

This loads the given module (can be NULL if no module needs to be loaded) and calls i2c_new_client_device() with the given i2c_adapter and chip/address arguments. If all goes well, then it registers the subdev with the v4l2_device.

You can also use the last argument of v4l2_i2c_new_subdev() to pass an array of possible I2C addresses that it should probe. These probe addresses are only used if the previous argument is 0. A non-zero argument means that you know the exact i2c address so in that case no probing will take place.

Both functions return NULL if something went wrong.

Note that the chipid you pass to v4l2_i2c_new_subdev() is usually the same as the module name. It allows you to specify a chip variant, e.g. “saa7114” or “saa7115”. In general though the i2c driver autodetects this. The use of chipid is something that needs to be looked at more closely at a later date. It differs between i2c drivers and as such can be confusing. To see which chip variants are supported you can look in the i2c driver code for the i2c_device_id table. This lists all the possibilities.

There are one more helper function:

v4l2_i2c_new_subdev_board() uses an i2c_board_info struct which is passed to the i2c driver and replaces the irq, platform_data and addr arguments.

If the subdev supports the s_config core ops, then that op is called with the irq and platform_data arguments after the subdev was setup.

The v4l2_i2c_new_subdev() function will call v4l2_i2c_new_subdev_board(), internally filling a i2c_board_info structure using the client_type and the addr to fill it.

2.11. Centrally managed subdev active state¶

Traditionally V4L2 subdev drivers maintained internal state for the active device configuration. This is often implemented as e.g. an array of struct v4l2_mbus_framefmt, one entry for each pad, and similarly for crop and compose rectangles.

In addition to the active configuration, each subdev file handle has a struct v4l2_subdev_state, managed by the V4L2 core, which contains the try configuration.

To simplify the subdev drivers the V4L2 subdev API now optionally supports a centrally managed active configuration represented by v4l2_subdev_state. One instance of state, which contains the active device configuration, is stored in the sub-device itself as part of the v4l2_subdev structure, while the core associates a try state to each open file handle, to store the try configuration related to that file handle.

Sub-device drivers can opt-in and use state to manage their active configuration by initializing the subdevice state with a call to v4l2_subdev_init_finalize() before registering the sub-device. They must also call v4l2_subdev_cleanup() to release all the allocated resources before unregistering the sub-device. The core automatically allocates and initializes a state for each open file handle to store the try configurations and frees it when closing the file handle.

V4L2 sub-device operations that use both the ACTIVE and TRY formats receive the correct state to operate on through the ‘state’ parameter. The state must be locked and unlocked by the caller by calling v4l2_subdev_lock_state() and v4l2_subdev_unlock_state(). The caller can do so by calling the subdev operation through the v4l2_subdev_call_state_active() macro.

Operations that do not receive a state parameter implicitly operate on the subdevice active state, which drivers can exclusively access by calling v4l2_subdev_lock_and_get_active_state(). The sub-device active state must equally be released by calling v4l2_subdev_unlock_state().

Drivers must never manually access the state stored in the v4l2_subdev or in the file handle without going through the designated helpers.

While the V4L2 core passes the correct try or active state to the subdevice operations, many existing device drivers pass a NULL state when calling operations with v4l2_subdev_call(). This legacy construct causes issues with subdevice drivers that let the V4L2 core manage the active state, as they expect to receive the appropriate state as a parameter. To help the conversion of subdevice drivers to a managed active state without having to convert all callers at the same time, an additional wrapper layer has been added to v4l2_subdev_call(), which handles the NULL case by getting and locking the callee’s active state with v4l2_subdev_lock_and_get_active_state(), and unlocking the state after the call.

The whole subdev state is in reality split into three parts: the v4l2_subdev_state, subdev controls and subdev driver’s internal state. In the future these parts should be combined into a single state. For the time being we need a way to handle the locking for these parts. This can be accomplished by sharing a lock. The v4l2_ctrl_handler already supports this via its ‘lock’ pointer and the same model is used with states. The driver can do the following before calling v4l2_subdev_init_finalize():

sd->ctrl_handler->lock = &priv->mutex;
sd->state_lock = &priv->mutex;

This shares the driver’s private mutex between the controls and the states.

2.12. Streams, multiplexed media pads and internal routing¶

A subdevice driver can implement support for multiplexed streams by setting the V4L2_SUBDEV_FL_STREAMS subdev flag and implementing support for centrally managed subdev active state, routing and stream based configuration.

2.13. V4L2 sub-device functions and data structures¶

struct v4l2_decode_vbi_line¶: used to decode_vbi_line

Definition:

struct v4l2_decode_vbi_line {
    u32 is_second_field;
    u8 *p;
    u32 line;
    u32 type;
};

Members

is_second_field: Set to 0 for the first (odd) field; set to 1 for the second (even) field.
p: Pointer to the sliced VBI data from the decoder. On exit, points to the start of the payload.
line: Line number of the sliced VBI data (1-23)
type: VBI service type (V4L2_SLICED_*). 0 if no service found

enum v4l2_subdev_io_pin_bits¶: Subdevice external IO pin configuration bits

Constants

V4L2_SUBDEV_IO_PIN_DISABLE: disables a pin config. ENABLE assumed.
V4L2_SUBDEV_IO_PIN_OUTPUT: set it if pin is an output.
V4L2_SUBDEV_IO_PIN_INPUT: set it if pin is an input.
V4L2_SUBDEV_IO_PIN_SET_VALUE: to set the output value via struct v4l2_subdev_io_pin_config->value.
V4L2_SUBDEV_IO_PIN_ACTIVE_LOW: pin active is bit 0. Otherwise, ACTIVE HIGH is assumed.

struct v4l2_subdev_io_pin_config¶: Subdevice external IO pin configuration

Definition:

struct v4l2_subdev_io_pin_config {
    u32 flags;
    u8 pin;
    u8 function;
    u8 value;
    u8 strength;
};

Members

flags: bitmask with flags for this pin’s config, whose bits are defined by enum v4l2_subdev_io_pin_bits.
pin: Chip external IO pin to configure
function: Internal signal pad/function to route to IO pin
value: Initial value for pin - e.g. GPIO output value
strength: Pin drive strength

struct v4l2_subdev_core_ops¶: Define core ops callbacks for subdevs

Definition:

struct v4l2_subdev_core_ops {
    int (*log_status)(struct v4l2_subdev *sd);
    int (*s_io_pin_config)(struct v4l2_subdev *sd, size_t n, struct v4l2_subdev_io_pin_config *pincfg);
    int (*init)(struct v4l2_subdev *sd, u32 val);
    int (*load_fw)(struct v4l2_subdev *sd);
    int (*reset)(struct v4l2_subdev *sd, u32 val);
    int (*s_gpio)(struct v4l2_subdev *sd, u32 val);
    long (*command)(struct v4l2_subdev *sd, unsigned int cmd, void *arg);
    long (*ioctl)(struct v4l2_subdev *sd, unsigned int cmd, void *arg);
#ifdef CONFIG_COMPAT;
    long (*compat_ioctl32)(struct v4l2_subdev *sd, unsigned int cmd, unsigned long arg);
#endif;
#ifdef CONFIG_VIDEO_ADV_DEBUG;
    int (*g_register)(struct v4l2_subdev *sd, struct v4l2_dbg_register *reg);
    int (*s_register)(struct v4l2_subdev *sd, const struct v4l2_dbg_register *reg);
#endif;
    int (*s_power)(struct v4l2_subdev *sd, int on);
    int (*interrupt_service_routine)(struct v4l2_subdev *sd, u32 status, bool *handled);
    int (*subscribe_event)(struct v4l2_subdev *sd, struct v4l2_fh *fh, struct v4l2_event_subscription *sub);
    int (*unsubscribe_event)(struct v4l2_subdev *sd, struct v4l2_fh *fh, struct v4l2_event_subscription *sub);
};

Members

log_status: callback for VIDIOC_LOG_STATUS() ioctl handler code.
s_io_pin_config: configure one or more chip I/O pins for chips that multiplex different internal signal pads out to IO pins. This function takes a pointer to an array of ‘n’ pin configuration entries, one for each pin being configured. This function could be called at times other than just subdevice initialization.
init: initialize the sensor registers to some sort of reasonable default values. Do not use for new drivers and should be removed in existing drivers.
load_fw: load firmware.
reset: generic reset command. The argument selects which subsystems to reset. Passing 0 will always reset the whole chip. Do not use for new drivers without discussing this first on the linux-media mailinglist. There should be no reason normally to reset a device.
s_gpio: set GPIO pins. Very simple right now, might need to be extended with a direction argument if needed.
command: called by in-kernel drivers in order to call functions internal to subdev drivers driver that have a separate callback.
ioctl: called at the end of ioctl() syscall handler at the V4L2 core. used to provide support for private ioctls used on the driver.
compat_ioctl32: called when a 32 bits application uses a 64 bits Kernel, in order to fix data passed from/to userspace.
g_register: callback for VIDIOC_DBG_G_REGISTER() ioctl handler code.
s_register: callback for VIDIOC_DBG_S_REGISTER() ioctl handler code.
s_power: puts subdevice in power saving mode (on == 0) or normal operation mode (on == 1). DEPRECATED. See Writing camera sensor drivers . pre_streamon and post_streamoff callbacks can be used for e.g. setting the bus to LP-11 mode before s_stream is called.
interrupt_service_routine: Called by the bridge chip’s interrupt service handler, when an interrupt status has be raised due to this subdev, so that this subdev can handle the details. It may schedule work to be performed later. It must not sleep. Called from an IRQ context.
subscribe_event: used by the drivers to request the control framework that for it to be warned when the value of a control changes.
unsubscribe_event: remove event subscription from the control framework.

struct v4l2_subdev_tuner_ops¶: Callbacks used when v4l device was opened in radio mode.

Definition:

struct v4l2_subdev_tuner_ops {
    int (*standby)(struct v4l2_subdev *sd);
    int (*s_radio)(struct v4l2_subdev *sd);
    int (*s_frequency)(struct v4l2_subdev *sd, const struct v4l2_frequency *freq);
    int (*g_frequency)(struct v4l2_subdev *sd, struct v4l2_frequency *freq);
    int (*enum_freq_bands)(struct v4l2_subdev *sd, struct v4l2_frequency_band *band);
    int (*g_tuner)(struct v4l2_subdev *sd, struct v4l2_tuner *vt);
    int (*s_tuner)(struct v4l2_subdev *sd, const struct v4l2_tuner *vt);
    int (*g_modulator)(struct v4l2_subdev *sd, struct v4l2_modulator *vm);
    int (*s_modulator)(struct v4l2_subdev *sd, const struct v4l2_modulator *vm);
    int (*s_type_addr)(struct v4l2_subdev *sd, struct tuner_setup *type);
    int (*s_config)(struct v4l2_subdev *sd, const struct v4l2_priv_tun_config *config);
};

Members

standby: puts the tuner in standby mode. It will be woken up automatically the next time it is used.
s_radio: callback that switches the tuner to radio mode. drivers should explicitly call it when a tuner ops should operate on radio mode, before being able to handle it. Used on devices that have both AM/FM radio receiver and TV.
s_frequency: callback for VIDIOC_S_FREQUENCY() ioctl handler code.
g_frequency: callback for VIDIOC_G_FREQUENCY() ioctl handler code. freq->type must be filled in. Normally done by video_ioctl2() or the bridge driver.
enum_freq_bands: callback for VIDIOC_ENUM_FREQ_BANDS() ioctl handler code.
g_tuner: callback for VIDIOC_G_TUNER() ioctl handler code.
s_tuner: callback for VIDIOC_S_TUNER() ioctl handler code. vt->type must be filled in. Normally done by video_ioctl2 or the bridge driver.
g_modulator: callback for VIDIOC_G_MODULATOR() ioctl handler code.
s_modulator: callback for VIDIOC_S_MODULATOR() ioctl handler code.
s_type_addr: sets tuner type and its I2C addr.
s_config: sets tda9887 specific stuff, like port1, port2 and qss

Description

Note

On devices that have both AM/FM and TV, it is up to the driver to explicitly call s_radio when the tuner should be switched to radio mode, before handling other struct v4l2_subdev_tuner_ops that would require it. An example of such usage is:

static void s_frequency(void *priv, const struct v4l2_frequency *f)
{
      ...
      if (f.type == V4L2_TUNER_RADIO)
              v4l2_device_call_all(v4l2_dev, 0, tuner, s_radio);
      ...
      v4l2_device_call_all(v4l2_dev, 0, tuner, s_frequency);
}

struct v4l2_subdev_audio_ops¶: Callbacks used for audio-related settings

Definition:

struct v4l2_subdev_audio_ops {
    int (*s_clock_freq)(struct v4l2_subdev *sd, u32 freq);
    int (*s_i2s_clock_freq)(struct v4l2_subdev *sd, u32 freq);
    int (*s_routing)(struct v4l2_subdev *sd, u32 input, u32 output, u32 config);
    int (*s_stream)(struct v4l2_subdev *sd, int enable);
};

Members

s_clock_freq: set the frequency (in Hz) of the audio clock output. Used to slave an audio processor to the video decoder, ensuring that audio and video remain synchronized. Usual values for the frequency are 48000, 44100 or 32000 Hz. If the frequency is not supported, then -EINVAL is returned.
s_i2s_clock_freq: sets I2S speed in bps. This is used to provide a standard way to select I2S clock used by driving digital audio streams at some board designs. Usual values for the frequency are 1024000 and 2048000. If the frequency is not supported, then -EINVAL is returned.
s_routing: used to define the input and/or output pins of an audio chip, and any additional configuration data. Never attempt to use user-level input IDs (e.g. Composite, S-Video, Tuner) at this level. An i2c device shouldn’t know about whether an input pin is connected to a Composite connector, become on another board or platform it might be connected to something else entirely. The calling driver is responsible for mapping a user-level input to the right pins on the i2c device.
s_stream: used to notify the audio code that stream will start or has stopped.

struct v4l2_mbus_frame_desc_entry_csi2¶

Definition:

struct v4l2_mbus_frame_desc_entry_csi2 {
    u8 vc;
    u8 dt;
};

Members

vc: CSI-2 virtual channel
dt: CSI-2 data type ID

enum v4l2_mbus_frame_desc_flags¶: media bus frame description flags

Constants

V4L2_MBUS_FRAME_DESC_FL_LEN_MAX

Indicates that struct v4l2_mbus_frame_desc_entry->length field specifies maximum data length.

V4L2_MBUS_FRAME_DESC_FL_BLOB

Indicates that the format does not have line offsets, i.e. the receiver should use 1D DMA.

struct v4l2_mbus_frame_desc_entry¶: media bus frame description structure

Definition:

struct v4l2_mbus_frame_desc_entry {
    enum v4l2_mbus_frame_desc_flags flags;
    u32 stream;
    u32 pixelcode;
    u32 length;
    union {
        struct v4l2_mbus_frame_desc_entry_csi2 csi2;
    } bus;
};

Members

flags: bitmask flags, as defined by enum v4l2_mbus_frame_desc_flags.
stream: stream in routing configuration
pixelcode: media bus pixel code, valid if flags FRAME_DESC_FL_BLOB is not set.
length: number of octets per frame, valid if flags V4L2_MBUS_FRAME_DESC_FL_LEN_MAX is set.
bus: Bus-specific frame descriptor parameters
bus.csi2: CSI-2-specific bus configuration

enum v4l2_mbus_frame_desc_type¶: media bus frame description type

Constants

V4L2_MBUS_FRAME_DESC_TYPE_UNDEFINED

Undefined frame desc type. Drivers should not use this, it is for backwards compatibility.

V4L2_MBUS_FRAME_DESC_TYPE_PARALLEL

Parallel media bus.

V4L2_MBUS_FRAME_DESC_TYPE_CSI2

CSI-2 media bus. Frame desc parameters must be set in struct v4l2_mbus_frame_desc_entry->csi2.

struct v4l2_mbus_frame_desc¶: media bus data frame description

Definition:

struct v4l2_mbus_frame_desc {
    enum v4l2_mbus_frame_desc_type type;
    struct v4l2_mbus_frame_desc_entry entry[V4L2_FRAME_DESC_ENTRY_MAX];
    unsigned short num_entries;
};

Members

type: type of the bus (enum v4l2_mbus_frame_desc_type)
entry: frame descriptors array
num_entries: number of entries in entry array

enum v4l2_subdev_pre_streamon_flags¶: Flags for pre_streamon subdev core op

Constants

V4L2_SUBDEV_PRE_STREAMON_FL_MANUAL_LP: Set the transmitter to either LP-11 or LP-111 mode before call to s_stream().

struct v4l2_subdev_video_ops¶: Callbacks used when v4l device was opened in video mode.

Definition:

struct v4l2_subdev_video_ops {
    int (*s_routing)(struct v4l2_subdev *sd, u32 input, u32 output, u32 config);
    int (*s_crystal_freq)(struct v4l2_subdev *sd, u32 freq, u32 flags);
    int (*g_std)(struct v4l2_subdev *sd, v4l2_std_id *norm);
    int (*s_std)(struct v4l2_subdev *sd, v4l2_std_id norm);
    int (*s_std_output)(struct v4l2_subdev *sd, v4l2_std_id std);
    int (*g_std_output)(struct v4l2_subdev *sd, v4l2_std_id *std);
    int (*querystd)(struct v4l2_subdev *sd, v4l2_std_id *std);
    int (*g_tvnorms)(struct v4l2_subdev *sd, v4l2_std_id *std);
    int (*g_tvnorms_output)(struct v4l2_subdev *sd, v4l2_std_id *std);
    int (*g_input_status)(struct v4l2_subdev *sd, u32 *status);
    int (*s_stream)(struct v4l2_subdev *sd, int enable);
    int (*g_pixelaspect)(struct v4l2_subdev *sd, struct v4l2_fract *aspect);
    int (*s_rx_buffer)(struct v4l2_subdev *sd, void *buf, unsigned int *size);
    int (*pre_streamon)(struct v4l2_subdev *sd, u32 flags);
    int (*post_streamoff)(struct v4l2_subdev *sd);
};

Members

s_routing

see s_routing in audio_ops, except this version is for video devices.

s_crystal_freq

sets the frequency of the crystal used to generate the clocks in Hz. An extra flags field allows device specific configuration regarding clock frequency dividers, etc. If not used, then set flags to 0. If the frequency is not supported, then -EINVAL is returned.

g_std

callback for VIDIOC_G_STD() ioctl handler code.

s_std

callback for VIDIOC_S_STD() ioctl handler code.

s_std_output

set v4l2_std_id for video OUTPUT devices. This is ignored by video input devices.

g_std_output

get current standard for video OUTPUT devices. This is ignored by video input devices.

querystd

callback for VIDIOC_QUERYSTD() ioctl handler code.

g_tvnorms

get v4l2_std_id with all standards supported by the video CAPTURE device. This is ignored by video output devices.

g_tvnorms_output

get v4l2_std_id with all standards supported by the video OUTPUT device. This is ignored by video capture devices.

g_input_status

get input status. Same as the status field in the struct v4l2_input

s_stream

start (enabled == 1) or stop (enabled == 0) streaming on the sub-device. Failure on stop will remove any resources acquired in streaming start, while the error code is still returned by the driver. The caller shall track the subdev state, and shall not start or stop an already started or stopped subdev. Also see call_s_stream wrapper in v4l2-subdev.c.

New drivers should instead implement v4l2_subdev_pad_ops.enable_streams and v4l2_subdev_pad_ops.disable_streams operations, and use v4l2_subdev_s_stream_helper for the v4l2_subdev_video_ops.s_stream operation to support legacy users.

Drivers should also not call the .s_stream() subdev operation directly, but use the v4l2_subdev_enable_streams() and v4l2_subdev_disable_streams() helpers.

g_pixelaspect

callback to return the pixelaspect ratio.

s_rx_buffer

set a host allocated memory buffer for the subdev. The subdev can adjust size to a lower value and must not write more data to the buffer starting at data than the original value of size.

pre_streamon

May be called before streaming is actually started, to help initialising the bus. Current usage is to set a CSI-2 transmitter to LP-11 or LP-111 mode before streaming. See enum v4l2_subdev_pre_streamon_flags.

pre_streamon shall return error if it cannot perform the operation as indicated by the flags argument. In particular, -EACCES indicates lack of support for the operation. The caller shall call post_streamoff for each successful call of pre_streamon.

post_streamoff

Called after streaming is stopped, but if and only if pre_streamon was called earlier.

struct v4l2_subdev_vbi_ops¶: Callbacks used when v4l device was opened in video mode via the vbi device node.

Definition:

struct v4l2_subdev_vbi_ops {
    int (*decode_vbi_line)(struct v4l2_subdev *sd, struct v4l2_decode_vbi_line *vbi_line);
    int (*s_vbi_data)(struct v4l2_subdev *sd, const struct v4l2_sliced_vbi_data *vbi_data);
    int (*g_vbi_data)(struct v4l2_subdev *sd, struct v4l2_sliced_vbi_data *vbi_data);
    int (*g_sliced_vbi_cap)(struct v4l2_subdev *sd, struct v4l2_sliced_vbi_cap *cap);
    int (*s_raw_fmt)(struct v4l2_subdev *sd, struct v4l2_vbi_format *fmt);
    int (*g_sliced_fmt)(struct v4l2_subdev *sd, struct v4l2_sliced_vbi_format *fmt);
    int (*s_sliced_fmt)(struct v4l2_subdev *sd, struct v4l2_sliced_vbi_format *fmt);
};

Members

decode_vbi_line: video decoders that support sliced VBI need to implement this ioctl. Field p of the struct v4l2_decode_vbi_line is set to the start of the VBI data that was generated by the decoder. The driver then parses the sliced VBI data and sets the other fields in the struct accordingly. The pointer p is updated to point to the start of the payload which can be copied verbatim into the data field of the struct v4l2_sliced_vbi_data. If no valid VBI data was found, then the type field is set to 0 on return.
s_vbi_data: used to generate VBI signals on a video signal. struct v4l2_sliced_vbi_data is filled with the data packets that should be output. Note that if you set the line field to 0, then that VBI signal is disabled. If no valid VBI data was found, then the type field is set to 0 on return.
g_vbi_data: used to obtain the sliced VBI packet from a readback register. Not all video decoders support this. If no data is available because the readback register contains invalid or erroneous data -EIO is returned. Note that you must fill in the ‘id’ member and the ‘field’ member (to determine whether CC data from the first or second field should be obtained).
g_sliced_vbi_cap: callback for VIDIOC_G_SLICED_VBI_CAP() ioctl handler code.
s_raw_fmt: setup the video encoder/decoder for raw VBI.
g_sliced_fmt: retrieve the current sliced VBI settings.
s_sliced_fmt: setup the sliced VBI settings.

struct v4l2_subdev_sensor_ops¶: v4l2-subdev sensor operations

Definition:

struct v4l2_subdev_sensor_ops {
    int (*g_skip_top_lines)(struct v4l2_subdev *sd, u32 *lines);
    int (*g_skip_frames)(struct v4l2_subdev *sd, u32 *frames);
};

Members

g_skip_top_lines: number of lines at the top of the image to be skipped. This is needed for some sensors, which always corrupt several top lines of the output image, or which send their metadata in them.
g_skip_frames: number of frames to skip at stream start. This is needed for buggy sensors that generate faulty frames when they are turned on.

enum v4l2_subdev_ir_mode¶: describes the type of IR supported

Constants

V4L2_SUBDEV_IR_MODE_PULSE_WIDTH: IR uses struct ir_raw_event records

struct v4l2_subdev_ir_parameters¶: Parameters for IR TX or TX

Definition:

struct v4l2_subdev_ir_parameters {
    unsigned int bytes_per_data_element;
    enum v4l2_subdev_ir_mode mode;
    bool enable;
    bool interrupt_enable;
    bool shutdown;
    bool modulation;
    u32 max_pulse_width;
    unsigned int carrier_freq;
    unsigned int duty_cycle;
    bool invert_level;
    bool invert_carrier_sense;
    u32 noise_filter_min_width;
    unsigned int carrier_range_lower;
    unsigned int carrier_range_upper;
    u32 resolution;
};

Members

bytes_per_data_element: bytes per data element of data in read or write call.
mode: IR mode as defined by enum v4l2_subdev_ir_mode.
enable: device is active if true
interrupt_enable: IR interrupts are enabled if true
shutdown: if true: set hardware to low/no power, false: normal mode
modulation: if true, it uses carrier, if false: baseband
max_pulse_width: maximum pulse width in ns, valid only for baseband signal
carrier_freq: carrier frequency in Hz, valid only for modulated signal
duty_cycle: duty cycle percentage, valid only for modulated signal
invert_level: invert signal level
invert_carrier_sense: Send 0/space as a carrier burst. used only in TX.
noise_filter_min_width: min time of a valid pulse, in ns. Used only for RX.
carrier_range_lower: Lower carrier range, in Hz, valid only for modulated signal. Used only for RX.
carrier_range_upper: Upper carrier range, in Hz, valid only for modulated signal. Used only for RX.
resolution: The receive resolution, in ns . Used only for RX.

struct v4l2_subdev_ir_ops¶: operations for IR subdevices

Definition:

struct v4l2_subdev_ir_ops {
    int (*rx_read)(struct v4l2_subdev *sd, u8 *buf, size_t count, ssize_t *num);
    int (*rx_g_parameters)(struct v4l2_subdev *sd, struct v4l2_subdev_ir_parameters *params);
    int (*rx_s_parameters)(struct v4l2_subdev *sd, struct v4l2_subdev_ir_parameters *params);
    int (*tx_write)(struct v4l2_subdev *sd, u8 *buf, size_t count, ssize_t *num);
    int (*tx_g_parameters)(struct v4l2_subdev *sd, struct v4l2_subdev_ir_parameters *params);
    int (*tx_s_parameters)(struct v4l2_subdev *sd, struct v4l2_subdev_ir_parameters *params);
};

Members

rx_read: Reads received codes or pulse width data. The semantics are similar to a non-blocking read() call.
rx_g_parameters: Get the current operating parameters and state of the IR receiver.
rx_s_parameters: Set the current operating parameters and state of the IR receiver. It is recommended to call [rt]x_g_parameters first to fill out the current state, and only change the fields that need to be changed. Upon return, the actual device operating parameters and state will be returned. Note that hardware limitations may prevent the actual settings from matching the requested settings - e.g. an actual carrier setting of 35,904 Hz when 36,000 Hz was requested. An exception is when the shutdown parameter is true. The last used operational parameters will be returned, but the actual state of the hardware be different to minimize power consumption and processing when shutdown is true.
tx_write: Writes codes or pulse width data for transmission. The semantics are similar to a non-blocking write() call.
tx_g_parameters: Get the current operating parameters and state of the IR transmitter.
tx_s_parameters: Set the current operating parameters and state of the IR transmitter. It is recommended to call [rt]x_g_parameters first to fill out the current state, and only change the fields that need to be changed. Upon return, the actual device operating parameters and state will be returned. Note that hardware limitations may prevent the actual settings from matching the requested settings - e.g. an actual carrier setting of 35,904 Hz when 36,000 Hz was requested. An exception is when the shutdown parameter is true. The last used operational parameters will be returned, but the actual state of the hardware be different to minimize power consumption and processing when shutdown is true.

struct v4l2_subdev_pad_config¶: Used for storing subdev pad information.

Definition:

struct v4l2_subdev_pad_config {
    struct v4l2_mbus_framefmt format;
    struct v4l2_rect crop;
    struct v4l2_rect compose;
    struct v4l2_fract interval;
};

Members

format: struct v4l2_mbus_framefmt
crop: struct v4l2_rect to be used for crop
compose: struct v4l2_rect to be used for compose
interval: frame interval

struct v4l2_subdev_stream_config¶: Used for storing stream configuration.

Definition:

struct v4l2_subdev_stream_config {
    u32 pad;
    u32 stream;
    bool enabled;
    struct v4l2_mbus_framefmt fmt;
    struct v4l2_rect crop;
    struct v4l2_rect compose;
    struct v4l2_fract interval;
};

Members

pad: pad number
stream: stream number
enabled: has the stream been enabled with v4l2_subdev_enable_streams()
fmt: struct v4l2_mbus_framefmt
crop: struct v4l2_rect to be used for crop
compose: struct v4l2_rect to be used for compose
interval: frame interval

Description

This structure stores configuration for a stream.

struct v4l2_subdev_stream_configs¶: A collection of stream configs.

Definition:

struct v4l2_subdev_stream_configs {
    u32 num_configs;
    struct v4l2_subdev_stream_config *configs;
};

Members

num_configs: number of entries in config.
configs: an array of struct v4l2_subdev_stream_configs.

struct v4l2_subdev_krouting¶: subdev routing table

Definition:

struct v4l2_subdev_krouting {
    unsigned int len_routes;
    unsigned int num_routes;
    struct v4l2_subdev_route *routes;
};

Members

len_routes: length of routes array, in routes
num_routes: number of routes
routes: struct v4l2_subdev_route

Description

This structure contains the routing table for a subdev.

struct v4l2_subdev_state¶: Used for storing subdev state information.

Definition:

struct v4l2_subdev_state {
    struct mutex _lock;
    struct mutex *lock;
    struct v4l2_subdev *sd;
    struct v4l2_subdev_pad_config *pads;
    struct v4l2_subdev_krouting routing;
    struct v4l2_subdev_stream_configs stream_configs;
};

Members

_lock: default for ‘lock’
lock: mutex for the state. May be replaced by the user.
sd: the sub-device which the state is related to
pads: struct v4l2_subdev_pad_config array
routing: routing table for the subdev
stream_configs: stream configurations (only for V4L2_SUBDEV_FL_STREAMS)

Description

This structure only needs to be passed to the pad op if the ‘which’ field of the main argument is set to V4L2_SUBDEV_FORMAT_TRY. For V4L2_SUBDEV_FORMAT_ACTIVE it is safe to pass NULL.

struct v4l2_subdev_pad_ops¶: v4l2-subdev pad level operations

Definition:

struct v4l2_subdev_pad_ops {
    int (*enum_mbus_code)(struct v4l2_subdev *sd,struct v4l2_subdev_state *state, struct v4l2_subdev_mbus_code_enum *code);
    int (*enum_frame_size)(struct v4l2_subdev *sd,struct v4l2_subdev_state *state, struct v4l2_subdev_frame_size_enum *fse);
    int (*enum_frame_interval)(struct v4l2_subdev *sd,struct v4l2_subdev_state *state, struct v4l2_subdev_frame_interval_enum *fie);
    int (*get_fmt)(struct v4l2_subdev *sd,struct v4l2_subdev_state *state, struct v4l2_subdev_format *format);
    int (*set_fmt)(struct v4l2_subdev *sd,struct v4l2_subdev_state *state, struct v4l2_subdev_format *format);
    int (*get_selection)(struct v4l2_subdev *sd,struct v4l2_subdev_state *state, struct v4l2_subdev_selection *sel);
    int (*set_selection)(struct v4l2_subdev *sd,struct v4l2_subdev_state *state, struct v4l2_subdev_selection *sel);
    int (*get_frame_interval)(struct v4l2_subdev *sd,struct v4l2_subdev_state *state, struct v4l2_subdev_frame_interval *interval);
    int (*set_frame_interval)(struct v4l2_subdev *sd,struct v4l2_subdev_state *state, struct v4l2_subdev_frame_interval *interval);
    int (*get_edid)(struct v4l2_subdev *sd, struct v4l2_edid *edid);
    int (*set_edid)(struct v4l2_subdev *sd, struct v4l2_edid *edid);
    int (*s_dv_timings)(struct v4l2_subdev *sd, unsigned int pad, struct v4l2_dv_timings *timings);
    int (*g_dv_timings)(struct v4l2_subdev *sd, unsigned int pad, struct v4l2_dv_timings *timings);
    int (*query_dv_timings)(struct v4l2_subdev *sd, unsigned int pad, struct v4l2_dv_timings *timings);
    int (*dv_timings_cap)(struct v4l2_subdev *sd, struct v4l2_dv_timings_cap *cap);
    int (*enum_dv_timings)(struct v4l2_subdev *sd, struct v4l2_enum_dv_timings *timings);
#ifdef CONFIG_MEDIA_CONTROLLER;
    int (*link_validate)(struct v4l2_subdev *sd, struct media_link *link,struct v4l2_subdev_format *source_fmt, struct v4l2_subdev_format *sink_fmt);
#endif ;
    int (*get_frame_desc)(struct v4l2_subdev *sd, unsigned int pad, struct v4l2_mbus_frame_desc *fd);
    int (*set_frame_desc)(struct v4l2_subdev *sd, unsigned int pad, struct v4l2_mbus_frame_desc *fd);
    int (*get_mbus_config)(struct v4l2_subdev *sd, unsigned int pad, struct v4l2_mbus_config *config);
    int (*set_routing)(struct v4l2_subdev *sd,struct v4l2_subdev_state *state,enum v4l2_subdev_format_whence which, struct v4l2_subdev_krouting *route);
    int (*enable_streams)(struct v4l2_subdev *sd,struct v4l2_subdev_state *state, u32 pad, u64 streams_mask);
    int (*disable_streams)(struct v4l2_subdev *sd,struct v4l2_subdev_state *state, u32 pad, u64 streams_mask);
};

Members

enum_mbus_code: callback for VIDIOC_SUBDEV_ENUM_MBUS_CODE() ioctl handler code.
enum_frame_size: callback for VIDIOC_SUBDEV_ENUM_FRAME_SIZE() ioctl handler code.
enum_frame_interval: callback for VIDIOC_SUBDEV_ENUM_FRAME_INTERVAL() ioctl handler code.
get_fmt: callback for VIDIOC_SUBDEV_G_FMT() ioctl handler code.
set_fmt: callback for VIDIOC_SUBDEV_S_FMT() ioctl handler code.
get_selection: callback for VIDIOC_SUBDEV_G_SELECTION() ioctl handler code.
set_selection: callback for VIDIOC_SUBDEV_S_SELECTION() ioctl handler code.
get_frame_interval: callback for VIDIOC_SUBDEV_G_FRAME_INTERVAL() ioctl handler code.
set_frame_interval: callback for VIDIOC_SUBDEV_S_FRAME_INTERVAL() ioctl handler code.
get_edid: callback for VIDIOC_SUBDEV_G_EDID() ioctl handler code.
set_edid: callback for VIDIOC_SUBDEV_S_EDID() ioctl handler code.
s_dv_timings: Set custom dv timings in the sub device. This is used when sub device is capable of setting detailed timing information in the hardware to generate/detect the video signal.
g_dv_timings: Get custom dv timings in the sub device.
query_dv_timings: callback for VIDIOC_QUERY_DV_TIMINGS() ioctl handler code.
dv_timings_cap: callback for VIDIOC_SUBDEV_DV_TIMINGS_CAP() ioctl handler code.
enum_dv_timings: callback for VIDIOC_SUBDEV_ENUM_DV_TIMINGS() ioctl handler code.
link_validate: used by the media controller code to check if the links that belongs to a pipeline can be used for stream.
get_frame_desc: get the current low level media bus frame parameters.
set_frame_desc: set the low level media bus frame parameters, fd array may be adjusted by the subdev driver to device capabilities.
get_mbus_config: get the media bus configuration of a remote sub-device. The media bus configuration is usually retrieved from the firmware interface at sub-device probe time, immediately applied to the hardware and eventually adjusted by the driver. Remote sub-devices (usually video receivers) shall use this operation to query the transmitting end bus configuration in order to adjust their own one accordingly. Callers should make sure they get the most up-to-date as possible configuration from the remote end, likely calling this operation as close as possible to stream on time. The operation shall fail if the pad index it has been called on is not valid or in case of unrecoverable failures.
set_routing: Enable or disable data connection routes described in the subdevice routing table. Subdevs that implement this operation must set the V4L2_SUBDEV_FL_STREAMS flag.
enable_streams: Enable the streams defined in streams_mask on the given source pad. Subdevs that implement this operation must use the active state management provided by the subdev core (enabled through a call to v4l2_subdev_init_finalize() at initialization time). Do not call directly, use v4l2_subdev_enable_streams() instead.
disable_streams: Disable the streams defined in streams_mask on the given source pad. Subdevs that implement this operation must use the active state management provided by the subdev core (enabled through a call to v4l2_subdev_init_finalize() at initialization time). Do not call directly, use v4l2_subdev_disable_streams() instead.

struct v4l2_subdev_ops¶: Subdev operations

Definition:

struct v4l2_subdev_ops {
    const struct v4l2_subdev_core_ops       *core;
    const struct v4l2_subdev_tuner_ops      *tuner;
    const struct v4l2_subdev_audio_ops      *audio;
    const struct v4l2_subdev_video_ops      *video;
    const struct v4l2_subdev_vbi_ops        *vbi;
    const struct v4l2_subdev_ir_ops         *ir;
    const struct v4l2_subdev_sensor_ops     *sensor;
    const struct v4l2_subdev_pad_ops        *pad;
};

Members

core: pointer to struct v4l2_subdev_core_ops. Can be NULL
tuner: pointer to struct v4l2_subdev_tuner_ops. Can be NULL
audio: pointer to struct v4l2_subdev_audio_ops. Can be NULL
video: pointer to struct v4l2_subdev_video_ops. Can be NULL
vbi: pointer to struct v4l2_subdev_vbi_ops. Can be NULL
ir: pointer to struct v4l2_subdev_ir_ops. Can be NULL
sensor: pointer to struct v4l2_subdev_sensor_ops. Can be NULL
pad: pointer to struct v4l2_subdev_pad_ops. Can be NULL

struct v4l2_subdev_internal_ops¶: V4L2 subdev internal ops

Definition:

struct v4l2_subdev_internal_ops {
    int (*init_state)(struct v4l2_subdev *sd, struct v4l2_subdev_state *state);
    int (*registered)(struct v4l2_subdev *sd);
    void (*unregistered)(struct v4l2_subdev *sd);
    int (*open)(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh);
    int (*close)(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh);
    void (*release)(struct v4l2_subdev *sd);
};

Members

init_state: initialize the subdev state to default values
registered: called when this subdev is registered. When called the v4l2_dev field is set to the correct v4l2_device.
unregistered: called when this subdev is unregistered. When called the v4l2_dev field is still set to the correct v4l2_device.
open: called when the subdev device node is opened by an application.
close: called when the subdev device node is closed. Please note that it is possible for close to be called after unregistered!
release: called when the last user of the subdev device is gone. This happens after the unregistered callback and when the last open filehandle to the v4l-subdevX device node was closed. If no device node was created for this sub-device, then the release callback is called right after the unregistered callback. The release callback is typically used to free the memory containing the v4l2_subdev structure. It is almost certainly required for any sub-device that sets the V4L2_SUBDEV_FL_HAS_DEVNODE flag.

Description

Note

Never call this from drivers, only the v4l2 framework can call these ops.

struct v4l2_subdev_platform_data¶: regulators config struct

Definition:

struct v4l2_subdev_platform_data {
    struct regulator_bulk_data *regulators;
    int num_regulators;
    void *host_priv;
};

Members

regulators: Optional regulators used to power on/off the subdevice
num_regulators: Number of regululators
host_priv: Per-subdevice data, specific for a certain video host device

struct v4l2_subdev¶: describes a V4L2 sub-device

Definition:

struct v4l2_subdev {
#if defined(CONFIG_MEDIA_CONTROLLER);
    struct media_entity entity;
#endif;
    struct list_head list;
    struct module *owner;
    bool owner_v4l2_dev;
    u32 flags;
    struct v4l2_device *v4l2_dev;
    const struct v4l2_subdev_ops *ops;
    const struct v4l2_subdev_internal_ops *internal_ops;
    struct v4l2_ctrl_handler *ctrl_handler;
    char name[52];
    u32 grp_id;
    void *dev_priv;
    void *host_priv;
    struct video_device *devnode;
    struct device *dev;
    struct fwnode_handle *fwnode;
    struct list_head async_list;
    struct list_head async_subdev_endpoint_list;
    struct v4l2_async_notifier *subdev_notifier;
    struct list_head asc_list;
    struct v4l2_subdev_platform_data *pdata;
    struct mutex *state_lock;
    struct led_classdev *privacy_led;
    struct v4l2_subdev_state *active_state;
    u64 enabled_pads;
    bool s_stream_enabled;
};

Members

entity: pointer to struct media_entity
list: List of sub-devices
owner: The owner is the same as the driver’s struct device owner.
owner_v4l2_dev: true if the sd->owner matches the owner of v4l2_dev->dev owner. Initialized by v4l2_device_register_subdev().
flags: subdev flags. Can be: V4L2_SUBDEV_FL_IS_I2C - Set this flag if this subdev is a i2c device; V4L2_SUBDEV_FL_IS_SPI - Set this flag if this subdev is a spi device; V4L2_SUBDEV_FL_HAS_DEVNODE - Set this flag if this subdev needs a device node; V4L2_SUBDEV_FL_HAS_EVENTS - Set this flag if this subdev generates events.
v4l2_dev: pointer to struct v4l2_device
ops: pointer to struct v4l2_subdev_ops
internal_ops: pointer to struct v4l2_subdev_internal_ops. Never call these internal ops from within a driver!
ctrl_handler: The control handler of this subdev. May be NULL.
name: Name of the sub-device. Please notice that the name must be unique.
grp_id: can be used to group similar subdevs. Value is driver-specific
dev_priv: pointer to private data
host_priv: pointer to private data used by the device where the subdev is attached.
devnode: subdev device node
dev: pointer to the physical device, if any
fwnode: The fwnode_handle of the subdev, usually the same as either dev->of_node->fwnode or dev->fwnode (whichever is non-NULL).
async_list: Links this subdev to a global subdev_list or notifier->done_list list.
async_subdev_endpoint_list: List entry in async_subdev_endpoint_entry of struct v4l2_async_subdev_endpoint.
subdev_notifier: A sub-device notifier implicitly registered for the sub- device using v4l2_async_register_subdev_sensor().
asc_list: Async connection list, of struct v4l2_async_connection.subdev_entry.
pdata: common part of subdevice platform data
state_lock: A pointer to a lock used for all the subdev’s states, set by the driver. This is optional. If NULL, each state instance will get a lock of its own.
privacy_led: Optional pointer to a LED classdev for the privacy LED for sensors.
active_state: Active state for the subdev (NULL for subdevs tracking the state internally). Initialized by calling v4l2_subdev_init_finalize().
enabled_pads: Bitmask of enabled pads used by v4l2_subdev_enable_streams() and v4l2_subdev_disable_streams() helper functions for fallback cases.
s_stream_enabled: Tracks whether streaming has been enabled with s_stream. This is only for call_s_stream() internal use.

Description

Each instance of a subdev driver should create this struct, either stand-alone or embedded in a larger struct.

This structure should be initialized by v4l2_subdev_init() or one of its variants: v4l2_spi_subdev_init(), v4l2_i2c_subdev_init().

media_entity_to_v4l2_subdev¶

media_entity_to_v4l2_subdev (ent)

Returns a struct v4l2_subdev from the struct media_entity embedded in it.

Parameters

ent: pointer to struct media_entity.

vdev_to_v4l2_subdev¶

vdev_to_v4l2_subdev (vdev)

Returns a struct v4l2_subdev from the struct video_device embedded on it.

Parameters

vdev: pointer to struct video_device

struct v4l2_subdev_fh¶: Used for storing subdev information per file handle

Definition:

struct v4l2_subdev_fh {
    struct v4l2_fh vfh;
    struct module *owner;
#if defined(CONFIG_VIDEO_V4L2_SUBDEV_API);
    struct v4l2_subdev_state *state;
    u64 client_caps;
#endif;
};

Members

vfh: pointer to struct v4l2_fh
owner: module pointer to the owner of this file handle
state: pointer to struct v4l2_subdev_state
client_caps: bitmask of V4L2_SUBDEV_CLIENT_CAP_*

to_v4l2_subdev_fh¶

to_v4l2_subdev_fh (fh)

Returns a struct v4l2_subdev_fh from the struct v4l2_fh embedded on it.

Parameters

fh: pointer to struct v4l2_fh

void v4l2_set_subdevdata(struct v4l2_subdev *sd, void *p)¶: Sets V4L2 dev private device data

Parameters

struct v4l2_subdev *sd: pointer to struct v4l2_subdev
void *p: pointer to the private device data to be stored.

void *v4l2_get_subdevdata(const struct v4l2_subdev *sd)¶: Gets V4L2 dev private device data

Parameters

const struct v4l2_subdev *sd: pointer to struct v4l2_subdev

Description

Returns the pointer to the private device data to be stored.

void v4l2_set_subdev_hostdata(struct v4l2_subdev *sd, void *p)¶: Sets V4L2 dev private host data

Parameters

struct v4l2_subdev *sd: pointer to struct v4l2_subdev
void *p: pointer to the private data to be stored.

void *v4l2_get_subdev_hostdata(const struct v4l2_subdev *sd)¶: Gets V4L2 dev private data

Parameters

const struct v4l2_subdev *sd: pointer to struct v4l2_subdev

Description

Returns the pointer to the private host data to be stored.

int v4l2_subdev_get_fwnode_pad_1_to_1(struct media_entity *entity, struct fwnode_endpoint *endpoint)¶: Get pad number from a subdev fwnode endpoint, assuming 1:1 port:pad

Parameters

struct media_entity *entity: Pointer to the subdev entity
struct fwnode_endpoint *endpoint: Pointer to a parsed fwnode endpoint

Description

This function can be used as the .get_fwnode_pad operation for subdevices that map port numbers and pad indexes 1:1. If the endpoint is owned by the subdevice, the function returns the endpoint port number.

Returns the endpoint port number on success or a negative error code.

int v4l2_subdev_link_validate_default(struct v4l2_subdev *sd, struct media_link *link, struct v4l2_subdev_format *source_fmt, struct v4l2_subdev_format *sink_fmt)¶: validates a media link

Parameters

struct v4l2_subdev *sd: pointer to struct v4l2_subdev
struct media_link *link: pointer to struct media_link
struct v4l2_subdev_format *source_fmt: pointer to struct v4l2_subdev_format
struct v4l2_subdev_format *sink_fmt: pointer to struct v4l2_subdev_format

Description

This function ensures that width, height and the media bus pixel code are equal on both source and sink of the link.

int v4l2_subdev_link_validate(struct media_link *link)¶: validates a media link

Parameters

struct media_link *link: pointer to struct media_link

Description

This function calls the subdev’s link_validate ops to validate if a media link is valid for streaming. It also internally calls v4l2_subdev_link_validate_default() to ensure that width, height and the media bus pixel code are equal on both source and sink of the link.

bool v4l2_subdev_has_pad_interdep(struct media_entity *entity, unsigned int pad0, unsigned int pad1)¶: MC has_pad_interdep implementation for subdevs

Parameters

struct media_entity *entity: pointer to struct media_entity
unsigned int pad0: pad number for the first pad
unsigned int pad1: pad number for the second pad

Description

This function is an implementation of the media_entity_operations.has_pad_interdep operation for subdevs that implement the multiplexed streams API (as indicated by the V4L2_SUBDEV_FL_STREAMS subdev flag).

It considers two pads interdependent if there is an active route between pad0 and pad1.

struct v4l2_subdev_state *__v4l2_subdev_state_alloc(struct v4l2_subdev *sd, const char *lock_name, struct lock_class_key *key)¶: allocate v4l2_subdev_state

Parameters

struct v4l2_subdev *sd: pointer to struct v4l2_subdev for which the state is being allocated.
const char *lock_name: name of the state lock
struct lock_class_key *key: lock_class_key for the lock

Description

Must call __v4l2_subdev_state_free() when state is no longer needed.

Not to be called directly by the drivers.

void __v4l2_subdev_state_free(struct v4l2_subdev_state *state)¶: free a v4l2_subdev_state

Parameters

struct v4l2_subdev_state *state: v4l2_subdev_state to be freed.

Description

Not to be called directly by the drivers.

v4l2_subdev_init_finalize¶

v4l2_subdev_init_finalize (sd)

Finalizes the initialization of the subdevice

Parameters

sd: The subdev

Description

This function finalizes the initialization of the subdev, including allocation of the active state for the subdev.

This function must be called by the subdev drivers that use the centralized active state, after the subdev struct has been initialized and media_entity_pads_init() has been called, but before registering the subdev.

The user must call v4l2_subdev_cleanup() when the subdev is being removed.

void v4l2_subdev_cleanup(struct v4l2_subdev *sd)¶: Releases the resources allocated by the subdevice

Parameters

struct v4l2_subdev *sd: The subdevice

Description

Clean up a V4L2 async sub-device. Must be called for a sub-device as part of its release if resources have been associated with it using v4l2_async_subdev_endpoint_add() or v4l2_subdev_init_finalize().

v4l2_subdev_state_get_format¶

v4l2_subdev_state_get_format (state, pad, ...)

Get pointer to a stream format

Parameters

state: subdevice state
pad: pad id
...: stream id (optional argument)

Description

This returns a pointer to struct v4l2_mbus_framefmt for the given pad + stream in the subdev state.

For stream-unaware drivers the format for the corresponding pad is returned. If the pad does not exist, NULL is returned.

v4l2_subdev_state_get_crop¶

v4l2_subdev_state_get_crop (state, pad, ...)

Get pointer to a stream crop rectangle

Parameters

state: subdevice state
pad: pad id
...: stream id (optional argument)

Description

This returns a pointer to crop rectangle for the given pad + stream in the subdev state.

For stream-unaware drivers the crop rectangle for the corresponding pad is returned. If the pad does not exist, NULL is returned.

v4l2_subdev_state_get_compose¶

v4l2_subdev_state_get_compose (state, pad, ...)

Get pointer to a stream compose rectangle

Parameters

state: subdevice state
pad: pad id
...: stream id (optional argument)

Description

This returns a pointer to compose rectangle for the given pad + stream in the subdev state.

For stream-unaware drivers the compose rectangle for the corresponding pad is returned. If the pad does not exist, NULL is returned.

v4l2_subdev_state_get_interval¶

v4l2_subdev_state_get_interval (state, pad, ...)

Get pointer to a stream frame interval

Parameters

state: subdevice state
pad: pad id
...: stream id (optional argument)

Description

This returns a pointer to the frame interval for the given pad + stream in the subdev state.

For stream-unaware drivers the frame interval for the corresponding pad is returned. If the pad does not exist, NULL is returned.

int v4l2_subdev_get_fmt(struct v4l2_subdev *sd, struct v4l2_subdev_state *state, struct v4l2_subdev_format *format)¶: Fill format based on state

Parameters

struct v4l2_subdev *sd: subdevice
struct v4l2_subdev_state *state: subdevice state
struct v4l2_subdev_format *format: pointer to struct v4l2_subdev_format

Description

Fill format->format field based on the information in the format struct.

This function can be used by the subdev drivers which support active state to implement v4l2_subdev_pad_ops.get_fmt if the subdev driver does not need to do anything special in their get_fmt op.

Returns 0 on success, error value otherwise.

int v4l2_subdev_get_frame_interval(struct v4l2_subdev *sd, struct v4l2_subdev_state *state, struct v4l2_subdev_frame_interval *fi)¶: Fill frame interval based on state

Parameters

struct v4l2_subdev *sd: subdevice
struct v4l2_subdev_state *state: subdevice state
struct v4l2_subdev_frame_interval *fi: pointer to struct v4l2_subdev_frame_interval

Description

Fill fi->interval field based on the information in the fi struct.

This function can be used by the subdev drivers which support active state to implement v4l2_subdev_pad_ops.get_frame_interval if the subdev driver does not need to do anything special in their get_frame_interval op.

Returns 0 on success, error value otherwise.

int v4l2_subdev_set_routing(struct v4l2_subdev *sd, struct v4l2_subdev_state *state, const struct v4l2_subdev_krouting *routing)¶: Set given routing to subdev state

Parameters

struct v4l2_subdev *sd: The subdevice
struct v4l2_subdev_state *state: The subdevice state
const struct v4l2_subdev_krouting *routing: Routing that will be copied to subdev state

Description

This will release old routing table (if any) from the state, allocate enough space for the given routing, and copy the routing.

This can be used from the subdev driver’s set_routing op, after validating the routing.

for_each_active_route¶

for_each_active_route (routing, route)

iterate on all active routes of a routing table

Parameters

routing: The routing table
route: The route iterator

int v4l2_subdev_set_routing_with_fmt(struct v4l2_subdev *sd, struct v4l2_subdev_state *state, const struct v4l2_subdev_krouting *routing, const struct v4l2_mbus_framefmt *fmt)¶: Set given routing and format to subdev state

Parameters

struct v4l2_subdev *sd: The subdevice
struct v4l2_subdev_state *state: The subdevice state
const struct v4l2_subdev_krouting *routing: Routing that will be copied to subdev state
const struct v4l2_mbus_framefmt *fmt: Format used to initialize all the streams

Description

This is the same as v4l2_subdev_set_routing, but additionally initializes all the streams using the given format.

int v4l2_subdev_routing_find_opposite_end(const struct v4l2_subdev_krouting *routing, u32 pad, u32 stream, u32 *other_pad, u32 *other_stream)¶: Find the opposite stream

Parameters

const struct v4l2_subdev_krouting *routing: routing used to find the opposite side
u32 pad: pad id
u32 stream: stream id
u32 *other_pad: pointer used to return the opposite pad
u32 *other_stream: pointer used to return the opposite stream

Description

This function uses the routing table to find the pad + stream which is opposite the given pad + stream.

other_pad and/or other_stream can be NULL if the caller does not need the value.

Returns 0 on success, or -EINVAL if no matching route is found.

struct v4l2_mbus_framefmt *v4l2_subdev_state_get_opposite_stream_format(struct v4l2_subdev_state *state, u32 pad, u32 stream)¶: Get pointer to opposite stream format

Parameters

struct v4l2_subdev_state *state: subdevice state
u32 pad: pad id
u32 stream: stream id

Description

This returns a pointer to struct v4l2_mbus_framefmt for the pad + stream that is opposite the given pad + stream in the subdev state.

If the state does not contain the given pad + stream, NULL is returned.

u64 v4l2_subdev_state_xlate_streams(const struct v4l2_subdev_state *state, u32 pad0, u32 pad1, u64 *streams)¶: Translate streams from one pad to another

Parameters

const struct v4l2_subdev_state *state: Subdevice state
u32 pad0: The first pad
u32 pad1: The second pad
u64 *streams: Streams bitmask on the first pad

Description

Streams on sink pads of a subdev are routed to source pads as expressed in the subdev state routing table. Stream numbers don’t necessarily match on the sink and source side of a route. This function translates stream numbers on pad0, expressed as a bitmask in streams, to the corresponding streams on pad1 using the routing table from the state. It returns the stream mask on pad1, and updates streams with the streams that have been found in the routing table.

pad0 and pad1 must be a sink and a source, in any order.

Return

The bitmask of streams of pad1 that are routed to streams on pad0.

enum v4l2_subdev_routing_restriction¶: Subdevice internal routing restrictions

Constants

V4L2_SUBDEV_ROUTING_NO_1_TO_N

an input stream shall not be routed to multiple output streams (stream duplication)

V4L2_SUBDEV_ROUTING_NO_N_TO_1

multiple input streams shall not be routed to the same output stream (stream merging)

V4L2_SUBDEV_ROUTING_NO_SINK_STREAM_MIX

all streams from a sink pad must be routed to a single source pad

V4L2_SUBDEV_ROUTING_NO_SOURCE_STREAM_MIX

all streams on a source pad must originate from a single sink pad

V4L2_SUBDEV_ROUTING_NO_SINK_MULTIPLEXING

sink pads shall not contain multiplexed streams

V4L2_SUBDEV_ROUTING_NO_SOURCE_MULTIPLEXING

source pads shall not contain multiplexed streams

V4L2_SUBDEV_ROUTING_ONLY_1_TO_1

only non-overlapping 1-to-1 stream routing is allowed (a combination of V4L2_SUBDEV_ROUTING_NO_1_TO_N and V4L2_SUBDEV_ROUTING_NO_N_TO_1)

V4L2_SUBDEV_ROUTING_NO_STREAM_MIX

all streams from a sink pad must be routed to a single source pad, and that source pad shall not get routes from any other sink pad (a combination of V4L2_SUBDEV_ROUTING_NO_SINK_STREAM_MIX and V4L2_SUBDEV_ROUTING_NO_SOURCE_STREAM_MIX)

V4L2_SUBDEV_ROUTING_NO_MULTIPLEXING

no multiplexed streams allowed on either source or sink sides.

int v4l2_subdev_routing_validate(struct v4l2_subdev *sd, const struct v4l2_subdev_krouting *routing, enum v4l2_subdev_routing_restriction disallow)¶: Verify that routes comply with driver constraints

Parameters

struct v4l2_subdev *sd: The subdevice
const struct v4l2_subdev_krouting *routing: Routing to verify
enum v4l2_subdev_routing_restriction disallow: Restrictions on routes

Description

This verifies that the given routing complies with the disallow constraints.

Returns 0 on success, error value otherwise.

int v4l2_subdev_enable_streams(struct v4l2_subdev *sd, u32 pad, u64 streams_mask)¶: Enable streams on a pad

Parameters

struct v4l2_subdev *sd: The subdevice
u32 pad: The pad
u64 streams_mask: Bitmask of streams to enable

Description

This function enables streams on a source pad of a subdevice. The pad is identified by its index, while the streams are identified by the streams_mask bitmask. This allows enabling multiple streams on a pad at once.

Enabling a stream that is already enabled isn’t allowed. If streams_mask contains an already enabled stream, this function returns -EALREADY without performing any operation.

Per-stream enable is only available for subdevs that implement the .enable_streams() and .disable_streams() operations. For other subdevs, this function implements a best-effort compatibility by calling the .s_stream() operation, limited to subdevs that have a single source pad.

Return

0: Success
-EALREADY: One of the streams in streams_mask is already enabled
-EINVAL: The pad index is invalid, or doesn’t correspond to a source pad
-EOPNOTSUPP: Falling back to the legacy .s_stream() operation is impossible because the subdev has multiple source pads

int v4l2_subdev_disable_streams(struct v4l2_subdev *sd, u32 pad, u64 streams_mask)¶: Disable streams on a pad

Parameters

struct v4l2_subdev *sd: The subdevice
u32 pad: The pad
u64 streams_mask: Bitmask of streams to disable

Description

This function disables streams on a source pad of a subdevice. The pad is identified by its index, while the streams are identified by the streams_mask bitmask. This allows disabling multiple streams on a pad at once.

Disabling a streams that is not enabled isn’t allowed. If streams_mask contains a disabled stream, this function returns -EALREADY without performing any operation.

Per-stream disable is only available for subdevs that implement the .enable_streams() and .disable_streams() operations. For other subdevs, this function implements a best-effort compatibility by calling the .s_stream() operation, limited to subdevs that have a single source pad.

Return

0: Success
-EALREADY: One of the streams in streams_mask is not enabled
-EINVAL: The pad index is invalid, or doesn’t correspond to a source pad
-EOPNOTSUPP: Falling back to the legacy .s_stream() operation is impossible because the subdev has multiple source pads

int v4l2_subdev_s_stream_helper(struct v4l2_subdev *sd, int enable)¶: Helper to implement the subdev s_stream operation using enable_streams and disable_streams

Parameters

struct v4l2_subdev *sd: The subdevice
int enable: Enable or disable streaming

Description

Subdevice drivers that implement the streams-aware v4l2_subdev_pad_ops.enable_streams and v4l2_subdev_pad_ops.disable_streams operations can use this helper to implement the legacy v4l2_subdev_video_ops.s_stream operation.

This helper can only be used by subdevs that have a single source pad.

Return

0 on success, or a negative error code otherwise.

void v4l2_subdev_lock_state(struct v4l2_subdev_state *state)¶: Locks the subdev state

Parameters

struct v4l2_subdev_state *state: The subdevice state

Description

Locks the given subdev state.

The state must be unlocked with v4l2_subdev_unlock_state() after use.

void v4l2_subdev_unlock_state(struct v4l2_subdev_state *state)¶: Unlocks the subdev state

Parameters

struct v4l2_subdev_state *state: The subdevice state

Description

Unlocks the given subdev state.

void v4l2_subdev_lock_states(struct v4l2_subdev_state *state1, struct v4l2_subdev_state *state2)¶: Lock two sub-device states

Parameters

struct v4l2_subdev_state *state1: One subdevice state
struct v4l2_subdev_state *state2: The other subdevice state

Description

Locks the state of two sub-devices.

The states must be unlocked with v4l2_subdev_unlock_states() after use.

This differs from calling v4l2_subdev_lock_state() on both states so that if the states share the same lock, the lock is acquired only once (so no deadlock occurs). The caller is responsible for ensuring the locks will always be acquired in the same order.

void v4l2_subdev_unlock_states(struct v4l2_subdev_state *state1, struct v4l2_subdev_state *state2)¶: Unlock two sub-device states

Parameters

struct v4l2_subdev_state *state1: One subdevice state
struct v4l2_subdev_state *state2: The other subdevice state

Description

Unlocks the state of two sub-devices.

This differs from calling v4l2_subdev_unlock_state() on both states so that if the states share the same lock, the lock is released only once.

struct v4l2_subdev_state *v4l2_subdev_get_unlocked_active_state(struct v4l2_subdev *sd)¶: Checks that the active subdev state is unlocked and returns it

Parameters

struct v4l2_subdev *sd: The subdevice

Description

Returns the active state for the subdevice, or NULL if the subdev does not support active state. If the state is not NULL, calls lockdep_assert_not_held() to issue a warning if the state is locked.

This function is to be used e.g. when getting the active state for the sole purpose of passing it forward, without accessing the state fields.

struct v4l2_subdev_state *v4l2_subdev_get_locked_active_state(struct v4l2_subdev *sd)¶: Checks that the active subdev state is locked and returns it

Parameters

struct v4l2_subdev *sd: The subdevice

Description

Returns the active state for the subdevice, or NULL if the subdev does not support active state. If the state is not NULL, calls lockdep_assert_held() to issue a warning if the state is not locked.

This function is to be used when the caller knows that the active state is already locked.

struct v4l2_subdev_state *v4l2_subdev_lock_and_get_active_state(struct v4l2_subdev *sd)¶: Locks and returns the active subdev state for the subdevice

Parameters

struct v4l2_subdev *sd: The subdevice

Description

Returns the locked active state for the subdevice, or NULL if the subdev does not support active state.

The state must be unlocked with v4l2_subdev_unlock_state() after use.

void v4l2_subdev_init(struct v4l2_subdev *sd, const struct v4l2_subdev_ops *ops)¶: initializes the sub-device struct

Parameters

struct v4l2_subdev *sd: pointer to the struct v4l2_subdev to be initialized
const struct v4l2_subdev_ops *ops: pointer to struct v4l2_subdev_ops.

v4l2_subdev_call¶

v4l2_subdev_call (sd, o, f, args...)

call an operation of a v4l2_subdev.

Parameters

sd: pointer to the struct v4l2_subdev
o: name of the element at struct v4l2_subdev_ops that contains f. Each element there groups a set of callbacks functions.
f: callback function to be called. The callback functions are defined in groups, according to each element at struct v4l2_subdev_ops.
args...: arguments for f.

Example

err = v4l2_subdev_call(sd, video, s_std, norm);

v4l2_subdev_call_state_active¶

v4l2_subdev_call_state_active (sd, o, f, args...)

call an operation of a v4l2_subdev which takes state as a parameter, passing the subdev its active state.

Parameters

sd: pointer to the struct v4l2_subdev
o: name of the element at struct v4l2_subdev_ops that contains f. Each element there groups a set of callbacks functions.
f: callback function to be called. The callback functions are defined in groups, according to each element at struct v4l2_subdev_ops.
args...: arguments for f.

Description

This is similar to v4l2_subdev_call(), except that this version can only be used for ops that take a subdev state as a parameter. The macro will get the active state, lock it before calling the op and unlock it after the call.

v4l2_subdev_call_state_try¶

v4l2_subdev_call_state_try (sd, o, f, args...)

call an operation of a v4l2_subdev which takes state as a parameter, passing the subdev a newly allocated try state.

Parameters

sd: pointer to the struct v4l2_subdev
o: name of the element at struct v4l2_subdev_ops that contains f. Each element there groups a set of callbacks functions.
f: callback function to be called. The callback functions are defined in groups, according to each element at struct v4l2_subdev_ops.
args...: arguments for f.

Description

This is similar to v4l2_subdev_call_state_active(), except that as this version allocates a new state, this is only usable for V4L2_SUBDEV_FORMAT_TRY use cases.

Note

only legacy non-MC drivers may need this macro.

v4l2_subdev_has_op¶

v4l2_subdev_has_op (sd, o, f)

Checks if a subdev defines a certain operation.

Parameters

sd: pointer to the struct v4l2_subdev
o: The group of callback functions in struct v4l2_subdev_ops which f is a part of.
f: callback function to be checked for its existence.

void v4l2_subdev_notify_event(struct v4l2_subdev *sd, const struct v4l2_event *ev)¶: Delivers event notification for subdevice

Parameters

struct v4l2_subdev *sd: The subdev for which to deliver the event
const struct v4l2_event *ev: The event to deliver

Description

Will deliver the specified event to all userspace event listeners which are subscribed to the v42l subdev event queue as well as to the bridge driver using the notify callback. The notification type for the notify callback will be V4L2_DEVICE_NOTIFY_EVENT.

bool v4l2_subdev_is_streaming(struct v4l2_subdev *sd)¶: Returns if the subdevice is streaming

Parameters

struct v4l2_subdev *sd: The subdevice

Description

v4l2_subdev_is_streaming() tells if the subdevice is currently streaming. “Streaming” here means whether .s_stream() or .enable_streams() has been successfully called, and the streaming has not yet been disabled.

If the subdevice implements .enable_streams() this function must be called while holding the active state lock.

The Linux Kernel

Contents

This Page

2.7. V4L2 sub-devices¶

2.7.1. Subdev registration¶

2.7.1.1. Registering synchronous sub-devices¶

2.7.1.2. Registering asynchronous sub-devices¶

2.7.1.3. Asynchronous sub-device notifiers¶

2.7.1.4. Asynchronous sub-device notifier for sub-devices¶

2.7.1.5. Asynchronous sub-device registration helper for camera sensor drivers¶

2.7.1.6. Asynchronous sub-device notifier example¶

2.7.1.7. Asynchronous sub-device notifier callbacks¶

2.7.2. Calling subdev operations¶

2.8. V4L2 sub-device userspace API¶

2.9. Read-only sub-device userspace API¶

2.10. I2C sub-device drivers¶

2.11. Centrally managed subdev active state¶

2.12. Streams, multiplexed media pads and internal routing¶

2.13. V4L2 sub-device functions and data structures¶