78418f300d
This introduces a module for working with faux devices in rust, along with adding sample code to show how the API is used. Unlike other types of devices, we don't provide any hooks for device probe/removal - since these are optional for the faux API and are unnecessary in rust. Signed-off-by: Lyude Paul <lyude@redhat.com> Cc: Maíra Canal <mairacanal@riseup.net> Cc: Danilo Krummrich <dakr@kernel.org> Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> Acked-by: Danilo Krummrich <dakr@kernel.org> Link: https://lore.kernel.org/r/2025021026-exert-accent-b4c6@gregkh Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
67 lines
2.6 KiB
Rust
67 lines
2.6 KiB
Rust
// SPDX-License-Identifier: GPL-2.0-only
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//! Abstractions for the faux bus.
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//!
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//! This module provides bindings for working with faux devices in kernel modules.
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//!
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//! C header: [`include/linux/device/faux.h`]
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use crate::{bindings, device, error::code::*, prelude::*};
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use core::ptr::{addr_of_mut, null, null_mut, NonNull};
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/// The registration of a faux device.
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///
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/// This type represents the registration of a [`struct faux_device`]. When an instance of this type
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/// is dropped, its respective faux device will be unregistered from the system.
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///
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/// # Invariants
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///
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/// `self.0` always holds a valid pointer to an initialized and registered [`struct faux_device`].
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///
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/// [`struct faux_device`]: srctree/include/linux/device/faux.h
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#[repr(transparent)]
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pub struct Registration(NonNull<bindings::faux_device>);
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impl Registration {
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/// Create and register a new faux device with the given name.
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pub fn new(name: &CStr) -> Result<Self> {
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// SAFETY:
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// - `name` is copied by this function into its own storage
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// - `faux_ops` is safe to leave NULL according to the C API
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let dev = unsafe { bindings::faux_device_create(name.as_char_ptr(), null_mut(), null()) };
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// The above function will return either a valid device, or NULL on failure
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// INVARIANT: The device will remain registered until faux_device_destroy() is called, which
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// happens in our Drop implementation.
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Ok(Self(NonNull::new(dev).ok_or(ENODEV)?))
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}
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fn as_raw(&self) -> *mut bindings::faux_device {
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self.0.as_ptr()
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}
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}
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impl AsRef<device::Device> for Registration {
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fn as_ref(&self) -> &device::Device {
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// SAFETY: The underlying `device` in `faux_device` is guaranteed by the C API to be
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// a valid initialized `device`.
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unsafe { device::Device::as_ref(addr_of_mut!((*self.as_raw()).dev)) }
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}
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}
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impl Drop for Registration {
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fn drop(&mut self) {
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// SAFETY: `self.0` is a valid registered faux_device via our type invariants.
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unsafe { bindings::faux_device_destroy(self.as_raw()) }
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}
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}
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// SAFETY: The faux device API is thread-safe as guaranteed by the device core, as long as
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// faux_device_destroy() is guaranteed to only be called once - which is guaranteed by our type not
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// having Copy/Clone.
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unsafe impl Send for Registration {}
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// SAFETY: The faux device API is thread-safe as guaranteed by the device core, as long as
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// faux_device_destroy() is guaranteed to only be called once - which is guaranteed by our type not
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// having Copy/Clone.
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unsafe impl Sync for Registration {}
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