rust: auxiliary: add auxiliary device / driver abstractions (ce735e73) · Commits · git / linux-net

MAINTAINERS

+2 −0

Original line number	Diff line number	Diff line
		@@ -3872,6 +3872,8 @@ T: git git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git
		F: Documentation/driver-api/auxiliary_bus.rst
		F: drivers/base/auxiliary.c
		F: include/linux/auxiliary_bus.h
		F: rust/helpers/auxiliary.c
		F: rust/kernel/auxiliary.rs

		AUXILIARY DISPLAY DRIVERS
		M: Andy Shevchenko <andy@kernel.org>

rust/bindings/bindings_helper.h

+1 −0

Original line number	Diff line number	Diff line
		@@ -7,6 +7,7 @@
		*/

		#include <kunit/test.h>
		#include <linux/auxiliary_bus.h>
		#include <linux/blk-mq.h>
		#include <linux/blk_types.h>
		#include <linux/blkdev.h>

rust/helpers/auxiliary.c

0 → 100644

+23 −0

Original line number	Diff line number	Diff line
		// SPDX-License-Identifier: GPL-2.0

		#include <linux/auxiliary_bus.h>

		void rust_helper_auxiliary_set_drvdata(struct auxiliary_device adev, void data)
		{
		auxiliary_set_drvdata(adev, data);
		}

		void rust_helper_auxiliary_get_drvdata(struct auxiliary_device adev)
		{
		return auxiliary_get_drvdata(adev);
		}

		void rust_helper_auxiliary_device_uninit(struct auxiliary_device *adev)
		{
		return auxiliary_device_uninit(adev);
		}

		void rust_helper_auxiliary_device_delete(struct auxiliary_device *adev)
		{
		return auxiliary_device_delete(adev);
		}

rust/helpers/helpers.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -7,6 +7,7 @@
		* Sorted alphabetically.
		*/

		#include "auxiliary.c"
		#include "blk.c"
		#include "bug.c"
		#include "build_assert.c"

rust/kernel/auxiliary.rs

0 → 100644

+274 −0

Original line number	Diff line number	Diff line
		// SPDX-License-Identifier: GPL-2.0

		//! Abstractions for the auxiliary bus.
		//!
		//! C header: [`include/linux/auxiliary_bus.h`](srctree/include/linux/auxiliary_bus.h)

		use crate::{
		bindings, device,
		device_id::RawDeviceId,
		driver,
		error::{to_result, Result},
		prelude::*,
		str::CStr,
		types::{ForeignOwnable, Opaque},
		ThisModule,
		};
		use core::{
		marker::PhantomData,
		ptr::{addr_of_mut, NonNull},
		};

		/// An adapter for the registration of auxiliary drivers.
		pub struct Adapter<T: Driver>(T);

		// SAFETY: A call to `unregister` for a given instance of `RegType` is guaranteed to be valid if
		// a preceding call to `register` has been successful.
		unsafe impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
		type RegType = bindings::auxiliary_driver;

		unsafe fn register(
		adrv: &Opaque<Self::RegType>,
		name: &'static CStr,
		module: &'static ThisModule,
		) -> Result {
		// SAFETY: It's safe to set the fields of `struct auxiliary_driver` on initialization.
		unsafe {
		(*adrv.get()).name = name.as_char_ptr();
		(*adrv.get()).probe = Some(Self::probe_callback);
		(*adrv.get()).remove = Some(Self::remove_callback);
		(*adrv.get()).id_table = T::ID_TABLE.as_ptr();
		}

		// SAFETY: `adrv` is guaranteed to be a valid `RegType`.
		to_result(unsafe {
		bindings::__auxiliary_driver_register(adrv.get(), module.0, name.as_char_ptr())
		})
		}

		unsafe fn unregister(adrv: &Opaque<Self::RegType>) {
		// SAFETY: `adrv` is guaranteed to be a valid `RegType`.
		unsafe { bindings::auxiliary_driver_unregister(adrv.get()) }
		}
		}

		impl<T: Driver + 'static> Adapter<T> {
		extern "C" fn probe_callback(
		adev: *mut bindings::auxiliary_device,
		id: *const bindings::auxiliary_device_id,
		) -> kernel::ffi::c_int {
		// SAFETY: The auxiliary bus only ever calls the probe callback with a valid pointer to a
		// `struct auxiliary_device`.
		//
		// INVARIANT: `adev` is valid for the duration of `probe_callback()`.
		let adev = unsafe { &*adev.cast::<Device<device::Core>>() };

		// SAFETY: `DeviceId` is a `#[repr(transparent)`] wrapper of `struct auxiliary_device_id`
		// and does not add additional invariants, so it's safe to transmute.
		let id = unsafe { &*id.cast::<DeviceId>() };
		let info = T::ID_TABLE.info(id.index());

		match T::probe(adev, info) {
		Ok(data) => {
		// Let the `struct auxiliary_device` own a reference of the driver's private data.
		// SAFETY: By the type invariant `adev.as_raw` returns a valid pointer to a
		// `struct auxiliary_device`.
		unsafe { bindings::auxiliary_set_drvdata(adev.as_raw(), data.into_foreign()) };
		}
		Err(err) => return Error::to_errno(err),
		}

		0
		}

		extern "C" fn remove_callback(adev: *mut bindings::auxiliary_device) {
		// SAFETY: The auxiliary bus only ever calls the remove callback with a valid pointer to a
		// `struct auxiliary_device`.
		let ptr = unsafe { bindings::auxiliary_get_drvdata(adev) };

		// SAFETY: `remove_callback` is only ever called after a successful call to
		// `probe_callback`, hence it's guaranteed that `ptr` points to a valid and initialized
		// `KBox<T>` pointer created through `KBox::into_foreign`.
		drop(unsafe { KBox::<T>::from_foreign(ptr) });
		}
		}

		/// Declares a kernel module that exposes a single auxiliary driver.
		#[macro_export]
		macro_rules! module_auxiliary_driver {
		($($f:tt)*) => {
		$crate::module_driver!(<T>, $crate::auxiliary::Adapter<T>, { $($f)* });
		};
		}

		/// Abstraction for `bindings::auxiliary_device_id`.
		#[repr(transparent)]
		#[derive(Clone, Copy)]
		pub struct DeviceId(bindings::auxiliary_device_id);

		impl DeviceId {
		/// Create a new [`DeviceId`] from name.
		pub const fn new(modname: &'static CStr, name: &'static CStr) -> Self {
		let name = name.as_bytes_with_nul();
		let modname = modname.as_bytes_with_nul();

		// TODO: Replace with `bindings::auxiliary_device_id::default()` once stabilized for
		// `const`.
		//
		// SAFETY: FFI type is valid to be zero-initialized.
		let mut id: bindings::auxiliary_device_id = unsafe { core::mem::zeroed() };

		let mut i = 0;
		while i < modname.len() {
		id.name[i] = modname[i];
		i += 1;
		}

		// Reuse the space of the NULL terminator.
		id.name[i - 1] = b'.';

		let mut j = 0;
		while j < name.len() {
		id.name[i] = name[j];
		i += 1;
		j += 1;
		}

		Self(id)
		}
		}

		// SAFETY:
		// * `DeviceId` is a `#[repr(transparent)`] wrapper of `auxiliary_device_id` and does not add
		// additional invariants, so it's safe to transmute to `RawType`.
		// * `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field.
		unsafe impl RawDeviceId for DeviceId {
		type RawType = bindings::auxiliary_device_id;

		const DRIVER_DATA_OFFSET: usize =
		core::mem::offset_of!(bindings::auxiliary_device_id, driver_data);

		fn index(&self) -> usize {
		self.0.driver_data
		}
		}

		/// IdTable type for auxiliary drivers.
		pub type IdTable<T> = &'static dyn kernel::device_id::IdTable<DeviceId, T>;

		/// Create a auxiliary `IdTable` with its alias for modpost.
		#[macro_export]
		macro_rules! auxiliary_device_table {
		($table_name:ident, $module_table_name:ident, $id_info_type: ty, $table_data: expr) => {
		const $table_name: $crate::device_id::IdArray<
		$crate::auxiliary::DeviceId,
		$id_info_type,
		{ $table_data.len() },
		> = $crate::device_id::IdArray::new($table_data);

		$crate::module_device_table!("auxiliary", $module_table_name, $table_name);
		};
		}

		/// The auxiliary driver trait.
		///
		/// Drivers must implement this trait in order to get an auxiliary driver registered.
		pub trait Driver {
		/// The type holding information about each device id supported by the driver.
		///
		/// TODO: Use associated_type_defaults once stabilized:
		///
		/// type IdInfo: 'static = ();
		type IdInfo: 'static;

		/// The table of device ids supported by the driver.
		const ID_TABLE: IdTable<Self::IdInfo>;

		/// Auxiliary driver probe.
		///
		/// Called when an auxiliary device is matches a corresponding driver.
		fn probe(dev: &Device<device::Core>, id_info: &Self::IdInfo) -> Result<Pin<KBox<Self>>>;
		}

		/// The auxiliary device representation.
		///
		/// This structure represents the Rust abstraction for a C `struct auxiliary_device`. The
		/// implementation abstracts the usage of an already existing C `struct auxiliary_device` within
		/// Rust code that we get passed from the C side.
		///
		/// # Invariants
		///
		/// A [`Device`] instance represents a valid `struct auxiliary_device` created by the C portion of
		/// the kernel.
		#[repr(transparent)]
		pub struct Device<Ctx: device::DeviceContext = device::Normal>(
		Opaque<bindings::auxiliary_device>,
		PhantomData<Ctx>,
		);

		impl<Ctx: device::DeviceContext> Device<Ctx> {
		fn as_raw(&self) -> *mut bindings::auxiliary_device {
		self.0.get()
		}

		/// Returns the auxiliary device' id.
		pub fn id(&self) -> u32 {
		// SAFETY: By the type invariant `self.as_raw()` is a valid pointer to a
		// `struct auxiliary_device`.
		unsafe { (*self.as_raw()).id }
		}

		/// Returns a reference to the parent [`device::Device`], if any.
		pub fn parent(&self) -> Option<&device::Device> {
		let ptr: *const Self = self;
		// CAST: `Device<Ctx: DeviceContext>` types are transparent to each other.
		let ptr: *const Device = ptr.cast();
		// SAFETY: `ptr` was derived from `&self`.
		let this = unsafe { &*ptr };

		this.as_ref().parent()
		}
		}

		// SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic
		// argument.
		kernel::impl_device_context_deref!(unsafe { Device });
		kernel::impl_device_context_into_aref!(Device);

		// SAFETY: Instances of `Device` are always reference-counted.
		unsafe impl crate::types::AlwaysRefCounted for Device {
		fn inc_ref(&self) {
		// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
		unsafe { bindings::get_device(self.as_ref().as_raw()) };
		}

		unsafe fn dec_ref(obj: NonNull<Self>) {
		// CAST: `Self` a transparent wrapper of `bindings::auxiliary_device`.
		let adev: *mut bindings::auxiliary_device = obj.cast().as_ptr();

		// SAFETY: By the type invariant of `Self`, `adev` is a pointer to a valid
		// `struct auxiliary_device`.
		let dev = unsafe { addr_of_mut!((*adev).dev) };

		// SAFETY: The safety requirements guarantee that the refcount is non-zero.
		unsafe { bindings::put_device(dev) }
		}
		}

		impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
		fn as_ref(&self) -> &device::Device<Ctx> {
		// SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
		// `struct auxiliary_device`.
		let dev = unsafe { addr_of_mut!((*self.as_raw()).dev) };

		// SAFETY: `dev` points to a valid `struct device`.
		unsafe { device::Device::as_ref(dev) }
		}
		}

		// SAFETY: A `Device` is always reference-counted and can be released from any thread.
		unsafe impl Send for Device {}

		// SAFETY: `Device` can be shared among threads because all methods of `Device`
		// (i.e. `Device<Normal>) are thread safe.
		unsafe impl Sync for Device {}