Merge tag 'v6.14-rc4' into next

Sync up with the mainline.

1 files changed, 165 insertions, 0 deletions

diff --git a/rust/kernel/device_id.rs b/rust/kernel/device_id.rs
new file mode 100644
index 000000000000..e5859217a579
--- /dev/null
+++ b/rust/kernel/device_id.rs
@@ -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()) };
+    };
+}