Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
rust: auxiliary: add auxiliary device / driver abstractions
Implement the basic auxiliary abstractions required to implement a
driver matching an auxiliary device.
The design and implementation is analogous to PCI and platform and is
based on the generic device / driver abstractions.
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Link: https://lore.kernel.org/r/20250414131934.28418-4-dakr@kernel.org
[ Fix typos, `let _ =` => `drop()`, use `kernel::ffi`. - Danilo ]
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
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MAINTAINERS
+2
MAINTAINERS
···
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F: Documentation/driver-api/auxiliary_bus.rst
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F: drivers/base/auxiliary.c
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F: include/linux/auxiliary_bus.h
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F: rust/helpers/auxiliary.c
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F: rust/kernel/auxiliary.rs
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AUXILIARY DISPLAY DRIVERS
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M: Andy Shevchenko <andy@kernel.org>
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rust/bindings/bindings_helper.h
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rust/bindings/bindings_helper.h
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rust/helpers/auxiliary.c
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rust/helpers/auxiliary.c
···
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// SPDX-License-Identifier: GPL-2.0
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#include <linux/auxiliary_bus.h>
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void rust_helper_auxiliary_set_drvdata(struct auxiliary_device *adev, void *data)
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{
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auxiliary_set_drvdata(adev, data);
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}
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void *rust_helper_auxiliary_get_drvdata(struct auxiliary_device *adev)
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{
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return auxiliary_get_drvdata(adev);
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}
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void rust_helper_auxiliary_device_uninit(struct auxiliary_device *adev)
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{
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return auxiliary_device_uninit(adev);
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}
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void rust_helper_auxiliary_device_delete(struct auxiliary_device *adev)
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{
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return auxiliary_device_delete(adev);
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}
+1
rust/helpers/helpers.c
+1
rust/helpers/helpers.c
+274
rust/kernel/auxiliary.rs
+274
rust/kernel/auxiliary.rs
···
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// SPDX-License-Identifier: GPL-2.0
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//! Abstractions for the auxiliary bus.
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//!
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//! C header: [`include/linux/auxiliary_bus.h`](srctree/include/linux/auxiliary_bus.h)
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use crate::{
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bindings, device,
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device_id::RawDeviceId,
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driver,
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error::{to_result, Result},
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prelude::*,
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str::CStr,
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types::{ForeignOwnable, Opaque},
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ThisModule,
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};
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use core::{
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marker::PhantomData,
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ptr::{addr_of_mut, NonNull},
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};
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/// An adapter for the registration of auxiliary drivers.
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pub struct Adapter<T: Driver>(T);
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+
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// SAFETY: A call to `unregister` for a given instance of `RegType` is guaranteed to be valid if
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// a preceding call to `register` has been successful.
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unsafe impl<T: Driver + 'static> driver::RegistrationOps for Adapter<T> {
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type RegType = bindings::auxiliary_driver;
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unsafe fn register(
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adrv: &Opaque<Self::RegType>,
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name: &'static CStr,
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module: &'static ThisModule,
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) -> Result {
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// SAFETY: It's safe to set the fields of `struct auxiliary_driver` on initialization.
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unsafe {
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(*adrv.get()).name = name.as_char_ptr();
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(*adrv.get()).probe = Some(Self::probe_callback);
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(*adrv.get()).remove = Some(Self::remove_callback);
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(*adrv.get()).id_table = T::ID_TABLE.as_ptr();
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}
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// SAFETY: `adrv` is guaranteed to be a valid `RegType`.
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to_result(unsafe {
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bindings::__auxiliary_driver_register(adrv.get(), module.0, name.as_char_ptr())
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})
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}
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unsafe fn unregister(adrv: &Opaque<Self::RegType>) {
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// SAFETY: `adrv` is guaranteed to be a valid `RegType`.
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unsafe { bindings::auxiliary_driver_unregister(adrv.get()) }
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}
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}
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impl<T: Driver + 'static> Adapter<T> {
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extern "C" fn probe_callback(
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adev: *mut bindings::auxiliary_device,
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id: *const bindings::auxiliary_device_id,
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) -> kernel::ffi::c_int {
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// SAFETY: The auxiliary bus only ever calls the probe callback with a valid pointer to a
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// `struct auxiliary_device`.
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//
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// INVARIANT: `adev` is valid for the duration of `probe_callback()`.
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let adev = unsafe { &*adev.cast::<Device<device::Core>>() };
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// SAFETY: `DeviceId` is a `#[repr(transparent)`] wrapper of `struct auxiliary_device_id`
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// and does not add additional invariants, so it's safe to transmute.
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let id = unsafe { &*id.cast::<DeviceId>() };
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let info = T::ID_TABLE.info(id.index());
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match T::probe(adev, info) {
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Ok(data) => {
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// Let the `struct auxiliary_device` own a reference of the driver's private data.
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// SAFETY: By the type invariant `adev.as_raw` returns a valid pointer to a
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// `struct auxiliary_device`.
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unsafe { bindings::auxiliary_set_drvdata(adev.as_raw(), data.into_foreign()) };
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}
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Err(err) => return Error::to_errno(err),
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}
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0
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}
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extern "C" fn remove_callback(adev: *mut bindings::auxiliary_device) {
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// SAFETY: The auxiliary bus only ever calls the remove callback with a valid pointer to a
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// `struct auxiliary_device`.
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let ptr = unsafe { bindings::auxiliary_get_drvdata(adev) };
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// SAFETY: `remove_callback` is only ever called after a successful call to
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// `probe_callback`, hence it's guaranteed that `ptr` points to a valid and initialized
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// `KBox<T>` pointer created through `KBox::into_foreign`.
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drop(unsafe { KBox::<T>::from_foreign(ptr) });
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}
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}
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/// Declares a kernel module that exposes a single auxiliary driver.
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#[macro_export]
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macro_rules! module_auxiliary_driver {
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($($f:tt)*) => {
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$crate::module_driver!(<T>, $crate::auxiliary::Adapter<T>, { $($f)* });
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};
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}
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/// Abstraction for `bindings::auxiliary_device_id`.
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#[repr(transparent)]
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#[derive(Clone, Copy)]
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pub struct DeviceId(bindings::auxiliary_device_id);
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impl DeviceId {
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/// Create a new [`DeviceId`] from name.
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pub const fn new(modname: &'static CStr, name: &'static CStr) -> Self {
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let name = name.as_bytes_with_nul();
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let modname = modname.as_bytes_with_nul();
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// TODO: Replace with `bindings::auxiliary_device_id::default()` once stabilized for
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// `const`.
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//
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// SAFETY: FFI type is valid to be zero-initialized.
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let mut id: bindings::auxiliary_device_id = unsafe { core::mem::zeroed() };
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let mut i = 0;
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while i < modname.len() {
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id.name[i] = modname[i];
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i += 1;
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}
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// Reuse the space of the NULL terminator.
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id.name[i - 1] = b'.';
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let mut j = 0;
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while j < name.len() {
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id.name[i] = name[j];
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i += 1;
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j += 1;
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}
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Self(id)
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}
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}
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// SAFETY:
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// * `DeviceId` is a `#[repr(transparent)`] wrapper of `auxiliary_device_id` and does not add
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// additional invariants, so it's safe to transmute to `RawType`.
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// * `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field.
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unsafe impl RawDeviceId for DeviceId {
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type RawType = bindings::auxiliary_device_id;
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const DRIVER_DATA_OFFSET: usize =
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core::mem::offset_of!(bindings::auxiliary_device_id, driver_data);
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fn index(&self) -> usize {
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self.0.driver_data
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}
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}
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/// IdTable type for auxiliary drivers.
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pub type IdTable<T> = &'static dyn kernel::device_id::IdTable<DeviceId, T>;
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/// Create a auxiliary `IdTable` with its alias for modpost.
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#[macro_export]
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macro_rules! auxiliary_device_table {
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($table_name:ident, $module_table_name:ident, $id_info_type: ty, $table_data: expr) => {
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const $table_name: $crate::device_id::IdArray<
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$crate::auxiliary::DeviceId,
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$id_info_type,
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{ $table_data.len() },
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> = $crate::device_id::IdArray::new($table_data);
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$crate::module_device_table!("auxiliary", $module_table_name, $table_name);
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};
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}
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/// The auxiliary driver trait.
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///
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/// Drivers must implement this trait in order to get an auxiliary driver registered.
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pub trait Driver {
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/// The type holding information about each device id supported by the driver.
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///
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/// TODO: Use associated_type_defaults once stabilized:
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///
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/// type IdInfo: 'static = ();
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type IdInfo: 'static;
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/// The table of device ids supported by the driver.
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const ID_TABLE: IdTable<Self::IdInfo>;
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/// Auxiliary driver probe.
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///
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/// Called when an auxiliary device is matches a corresponding driver.
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fn probe(dev: &Device<device::Core>, id_info: &Self::IdInfo) -> Result<Pin<KBox<Self>>>;
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}
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/// The auxiliary device representation.
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///
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/// This structure represents the Rust abstraction for a C `struct auxiliary_device`. The
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/// implementation abstracts the usage of an already existing C `struct auxiliary_device` within
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/// Rust code that we get passed from the C side.
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///
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/// # Invariants
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///
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/// A [`Device`] instance represents a valid `struct auxiliary_device` created by the C portion of
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/// the kernel.
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#[repr(transparent)]
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pub struct Device<Ctx: device::DeviceContext = device::Normal>(
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Opaque<bindings::auxiliary_device>,
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PhantomData<Ctx>,
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);
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impl<Ctx: device::DeviceContext> Device<Ctx> {
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fn as_raw(&self) -> *mut bindings::auxiliary_device {
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self.0.get()
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}
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/// Returns the auxiliary device' id.
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pub fn id(&self) -> u32 {
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// SAFETY: By the type invariant `self.as_raw()` is a valid pointer to a
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// `struct auxiliary_device`.
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unsafe { (*self.as_raw()).id }
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}
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/// Returns a reference to the parent [`device::Device`], if any.
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pub fn parent(&self) -> Option<&device::Device> {
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let ptr: *const Self = self;
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// CAST: `Device<Ctx: DeviceContext>` types are transparent to each other.
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let ptr: *const Device = ptr.cast();
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// SAFETY: `ptr` was derived from `&self`.
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let this = unsafe { &*ptr };
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this.as_ref().parent()
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}
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}
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// SAFETY: `Device` is a transparent wrapper of a type that doesn't depend on `Device`'s generic
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// argument.
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kernel::impl_device_context_deref!(unsafe { Device });
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kernel::impl_device_context_into_aref!(Device);
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+
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// SAFETY: Instances of `Device` are always reference-counted.
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unsafe impl crate::types::AlwaysRefCounted for Device {
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fn inc_ref(&self) {
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// SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
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unsafe { bindings::get_device(self.as_ref().as_raw()) };
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}
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unsafe fn dec_ref(obj: NonNull<Self>) {
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// CAST: `Self` a transparent wrapper of `bindings::auxiliary_device`.
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let adev: *mut bindings::auxiliary_device = obj.cast().as_ptr();
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// SAFETY: By the type invariant of `Self`, `adev` is a pointer to a valid
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// `struct auxiliary_device`.
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let dev = unsafe { addr_of_mut!((*adev).dev) };
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// SAFETY: The safety requirements guarantee that the refcount is non-zero.
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unsafe { bindings::put_device(dev) }
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}
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}
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impl<Ctx: device::DeviceContext> AsRef<device::Device<Ctx>> for Device<Ctx> {
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fn as_ref(&self) -> &device::Device<Ctx> {
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// SAFETY: By the type invariant of `Self`, `self.as_raw()` is a pointer to a valid
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// `struct auxiliary_device`.
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let dev = unsafe { addr_of_mut!((*self.as_raw()).dev) };
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+
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// SAFETY: `dev` points to a valid `struct device`.
265
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unsafe { device::Device::as_ref(dev) }
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}
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}
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+
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// SAFETY: A `Device` is always reference-counted and can be released from any thread.
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unsafe impl Send for Device {}
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+
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// SAFETY: `Device` can be shared among threads because all methods of `Device`
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// (i.e. `Device<Normal>) are thread safe.
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unsafe impl Sync for Device {}
-1
rust/kernel/device.rs
-1
rust/kernel/device.rs