@@ -7033,6 +7033,7 @@ F: include/linux/kobj*
F: include/linux/property.h
F: lib/kobj*
F: rust/kernel/device.rs
+F: rust/kernel/device_id.rs
F: rust/kernel/driver.rs
DRIVERS FOR OMAP ADAPTIVE VOLTAGE SCALING (AVS)
new file mode 100644
@@ -0,0 +1,165 @@
+// SPDX-License-Identifier: GPL-2.0
+
+//! Generic implementation of device IDs.
+//!
+//! Each bus / subsystem that matches device and driver through a bus / subsystem specific ID is
+//! expected to implement [`RawDeviceId`].
+
+use core::mem::MaybeUninit;
+
+/// Marker trait to indicate a Rust device ID type represents a corresponding C device ID type.
+///
+/// This is meant to be implemented by buses/subsystems so that they can use [`IdTable`] to
+/// guarantee (at compile-time) zero-termination of device id tables provided by drivers.
+///
+/// # Safety
+///
+/// Implementers must ensure that:
+/// - `Self` is layout-compatible with [`RawDeviceId::RawType`]; i.e. it's safe to transmute to
+/// `RawDeviceId`.
+///
+/// This requirement is needed so `IdArray::new` can convert `Self` to `RawType` when building
+/// the ID table.
+///
+/// Ideally, this should be achieved using a const function that does conversion instead of
+/// transmute; however, const trait functions relies on `const_trait_impl` unstable feature,
+/// which is broken/gone in Rust 1.73.
+///
+/// - `DRIVER_DATA_OFFSET` is the offset of context/data field of the device ID (usually named
+/// `driver_data`) of the device ID, the field is suitable sized to write a `usize` value.
+///
+/// Similar to the previous requirement, the data should ideally be added during `Self` to
+/// `RawType` conversion, but there's currently no way to do it when using traits in const.
+pub unsafe trait RawDeviceId {
+ /// The raw type that holds the device id.
+ ///
+ /// Id tables created from [`Self`] are going to hold this type in its zero-terminated array.
+ type RawType: Copy;
+
+ /// The offset to the context/data field.
+ const DRIVER_DATA_OFFSET: usize;
+
+ /// The index stored at `DRIVER_DATA_OFFSET` of the implementor of the [`RawDeviceId`] trait.
+ fn index(&self) -> usize;
+}
+
+/// A zero-terminated device id array.
+#[repr(C)]
+pub struct RawIdArray<T: RawDeviceId, const N: usize> {
+ ids: [T::RawType; N],
+ sentinel: MaybeUninit<T::RawType>,
+}
+
+impl<T: RawDeviceId, const N: usize> RawIdArray<T, N> {
+ #[doc(hidden)]
+ pub const fn size(&self) -> usize {
+ core::mem::size_of::<Self>()
+ }
+}
+
+/// A zero-terminated device id array, followed by context data.
+#[repr(C)]
+pub struct IdArray<T: RawDeviceId, U, const N: usize> {
+ raw_ids: RawIdArray<T, N>,
+ id_infos: [U; N],
+}
+
+impl<T: RawDeviceId, U, const N: usize> IdArray<T, U, N> {
+ /// Creates a new instance of the array.
+ ///
+ /// The contents are derived from the given identifiers and context information.
+ pub const fn new(ids: [(T, U); N]) -> Self {
+ let mut raw_ids = [const { MaybeUninit::<T::RawType>::uninit() }; N];
+ let mut infos = [const { MaybeUninit::uninit() }; N];
+
+ let mut i = 0usize;
+ while i < N {
+ // SAFETY: by the safety requirement of `RawDeviceId`, we're guaranteed that `T` is
+ // layout-wise compatible with `RawType`.
+ raw_ids[i] = unsafe { core::mem::transmute_copy(&ids[i].0) };
+ // SAFETY: by the safety requirement of `RawDeviceId`, this would be effectively
+ // `raw_ids[i].driver_data = i;`.
+ unsafe {
+ raw_ids[i]
+ .as_mut_ptr()
+ .byte_offset(T::DRIVER_DATA_OFFSET as _)
+ .cast::<usize>()
+ .write(i);
+ }
+
+ // SAFETY: this is effectively a move: `infos[i] = ids[i].1`. We make a copy here but
+ // later forget `ids`.
+ infos[i] = MaybeUninit::new(unsafe { core::ptr::read(&ids[i].1) });
+ i += 1;
+ }
+
+ core::mem::forget(ids);
+
+ Self {
+ raw_ids: RawIdArray {
+ // SAFETY: this is effectively `array_assume_init`, which is unstable, so we use
+ // `transmute_copy` instead. We have initialized all elements of `raw_ids` so this
+ // `array_assume_init` is safe.
+ ids: unsafe { core::mem::transmute_copy(&raw_ids) },
+ sentinel: MaybeUninit::zeroed(),
+ },
+ // SAFETY: We have initialized all elements of `infos` so this `array_assume_init` is
+ // safe.
+ id_infos: unsafe { core::mem::transmute_copy(&infos) },
+ }
+ }
+
+ /// Reference to the contained [`RawIdArray`].
+ pub const fn raw_ids(&self) -> &RawIdArray<T, N> {
+ &self.raw_ids
+ }
+}
+
+/// A device id table.
+///
+/// This trait is only implemented by `IdArray`.
+///
+/// The purpose of this trait is to allow `&'static dyn IdArray<T, U>` to be in context when `N` in
+/// `IdArray` doesn't matter.
+pub trait IdTable<T: RawDeviceId, U> {
+ /// Obtain the pointer to the ID table.
+ fn as_ptr(&self) -> *const T::RawType;
+
+ /// Obtain the pointer to the bus specific device ID from an index.
+ fn id(&self, index: usize) -> &T::RawType;
+
+ /// Obtain the pointer to the driver-specific information from an index.
+ fn info(&self, index: usize) -> &U;
+}
+
+impl<T: RawDeviceId, U, const N: usize> IdTable<T, U> for IdArray<T, U, N> {
+ fn as_ptr(&self) -> *const T::RawType {
+ // This cannot be `self.ids.as_ptr()`, as the return pointer must have correct provenance
+ // to access the sentinel.
+ (self as *const Self).cast()
+ }
+
+ fn id(&self, index: usize) -> &T::RawType {
+ &self.raw_ids.ids[index]
+ }
+
+ fn info(&self, index: usize) -> &U {
+ &self.id_infos[index]
+ }
+}
+
+/// Create device table alias for modpost.
+#[macro_export]
+macro_rules! module_device_table {
+ ($table_type: literal, $module_table_name:ident, $table_name:ident) => {
+ #[rustfmt::skip]
+ #[export_name =
+ concat!("__mod_device_table__", $table_type,
+ "__", module_path!(),
+ "_", line!(),
+ "_", stringify!($table_name))
+ ]
+ static $module_table_name: [core::mem::MaybeUninit<u8>; $table_name.raw_ids().size()] =
+ unsafe { core::mem::transmute_copy($table_name.raw_ids()) };
+ };
+}
@@ -18,6 +18,11 @@
#![feature(inline_const)]
#![feature(lint_reasons)]
#![feature(unsize)]
+// Stable in Rust 1.83
+#![feature(const_maybe_uninit_as_mut_ptr)]
+#![feature(const_mut_refs)]
+#![feature(const_ptr_write)]
+#![feature(const_refs_to_cell)]
// Ensure conditional compilation based on the kernel configuration works;
// otherwise we may silently break things like initcall handling.
@@ -35,6 +40,7 @@
mod build_assert;
pub mod cred;
pub mod device;
+pub mod device_id;
pub mod driver;
pub mod error;
#[cfg(CONFIG_RUST_FW_LOADER_ABSTRACTIONS)]