kernel/
faux.rs

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1// SPDX-License-Identifier: GPL-2.0-only
2
3//! Abstractions for the faux bus.
4//!
5//! This module provides bindings for working with faux devices in kernel modules.
6//!
7//! C header: [`include/linux/device/faux.h`]
8
9use crate::{bindings, device, error::code::*, prelude::*};
10use core::ptr::{addr_of_mut, null, null_mut, NonNull};
11
12/// The registration of a faux device.
13///
14/// This type represents the registration of a [`struct faux_device`]. When an instance of this type
15/// is dropped, its respective faux device will be unregistered from the system.
16///
17/// # Invariants
18///
19/// `self.0` always holds a valid pointer to an initialized and registered [`struct faux_device`].
20///
21/// [`struct faux_device`]: srctree/include/linux/device/faux.h
22#[repr(transparent)]
23pub struct Registration(NonNull<bindings::faux_device>);
24
25impl Registration {
26    /// Create and register a new faux device with the given name.
27    pub fn new(name: &CStr) -> Result<Self> {
28        // SAFETY:
29        // - `name` is copied by this function into its own storage
30        // - `faux_ops` is safe to leave NULL according to the C API
31        let dev = unsafe { bindings::faux_device_create(name.as_char_ptr(), null_mut(), null()) };
32
33        // The above function will return either a valid device, or NULL on failure
34        // INVARIANT: The device will remain registered until faux_device_destroy() is called, which
35        // happens in our Drop implementation.
36        Ok(Self(NonNull::new(dev).ok_or(ENODEV)?))
37    }
38
39    fn as_raw(&self) -> *mut bindings::faux_device {
40        self.0.as_ptr()
41    }
42}
43
44impl AsRef<device::Device> for Registration {
45    fn as_ref(&self) -> &device::Device {
46        // SAFETY: The underlying `device` in `faux_device` is guaranteed by the C API to be
47        // a valid initialized `device`.
48        unsafe { device::Device::as_ref(addr_of_mut!((*self.as_raw()).dev)) }
49    }
50}
51
52impl Drop for Registration {
53    fn drop(&mut self) {
54        // SAFETY: `self.0` is a valid registered faux_device via our type invariants.
55        unsafe { bindings::faux_device_destroy(self.as_raw()) }
56    }
57}
58
59// SAFETY: The faux device API is thread-safe as guaranteed by the device core, as long as
60// faux_device_destroy() is guaranteed to only be called once - which is guaranteed by our type not
61// having Copy/Clone.
62unsafe impl Send for Registration {}
63
64// SAFETY: The faux device API is thread-safe as guaranteed by the device core, as long as
65// faux_device_destroy() is guaranteed to only be called once - which is guaranteed by our type not
66// having Copy/Clone.
67unsafe impl Sync for Registration {}
kernel/faux.rs

kernel/
faux.rs
