Merge tag 'drm-rust-next-2025-09-16' of https://gitlab.freedesktop.org/drm/rust/kernel into drm-next

DRM Rust changes for v6.18

Alloc
  - Add BorrowedPage type and AsPageIter trait
  - Implement Vmalloc::to_page() and VmallocPageIter
  - Implement AsPageIter for VBox and VVec

DMA & Scatterlist
  - Add dma::DataDirection and type alias for dma_addr_t
  - Abstraction for struct scatterlist and struct sg_table

DRM
  - In the DRM GEM module, simplify overall use of generics, add
    DriverFile type alias and drop Object::SIZE.

Nova (Core)
  - Various register!() macro improvements (paving the way for lifting
    it to common driver infrastructure)
  - Minor VBios fixes and refactoring
  - Minor firmware request refactoring
  - Advance firmware boot stages; process Booter and patch its
    signature, process GSP and GSP bootloader
  - Switch development fimrware version to r570.144
  - Add basic firmware bindings for r570.144
  - Move GSP boot code to its own module
  - Clean up and take advantage of pin-init features to store most of
    the driver's private data within a single allocation
  - Update ARef import from sync::aref
  - Add website to MAINTAINERS entry

Nova (DRM)
  - Update ARef import from sync::aref
  - Add website to MAINTAINERS entry

Pin-Init
  - Merge pin-init PR from Benno
    - `#[pin_data]` now generates a `*Projection` struct similar to the
      `pin-project` crate.

    - Add initializer code blocks to `[try_][pin_]init!` macros: make
      initializer macros accept any number of `_: {/* arbitrary code
      */},` & make them run the code at that point.

    - Make the `[try_][pin_]init!` macros expose initialized fields via
      a `let` binding as `&mut T` or `Pin<&mut T>` for later fields.

Rust
  - Various methods for AsBytes and FromBytes traits

Tyr
  - Initial Rust driver skeleton for ARM Mali GPUs.
    - It can power up the GPU, query for GPU metatdata through MMIO and
      provide the metadata to userspace via DRM device IOCTL (struct
      drm_panthor_dev_query).

Signed-off-by: Dave Airlie <airlied@redhat.com>

From: "Danilo Krummrich" <dakr@kernel.org>
Link: https://lore.kernel.org/r/DCUC4SY6SRBD.1ZLHAIQZOC6KG@kernel.org

1 files changed, 112 insertions, 2 deletions

diff --git a/rust/kernel/transmute.rs b/rust/kernel/transmute.rs
index 1c7d43771a37..cfc37d81adf2 100644
--- a/rust/kernel/transmute.rs
+++ b/rust/kernel/transmute.rs
@@ -2,6 +2,8 @@
 
 //! Traits for transmuting types.
 
+use core::mem::size_of;
+
 /// Types for which any bit pattern is valid.
 ///
 /// Not all types are valid for all values. For example, a `bool` must be either zero or one, so
@@ -9,10 +11,93 @@
 ///
 /// It's okay for the type to have padding, as initializing those bytes has no effect.
 ///
+/// # Examples
+///
+/// ```
+/// use kernel::transmute::FromBytes;
+///
+/// # fn test() -> Option<()> {
+/// let raw = [1, 2, 3, 4];
+///
+/// let result = u32::from_bytes(&raw)?;
+///
+/// #[cfg(target_endian = "little")]
+/// assert_eq!(*result, 0x4030201);
+///
+/// #[cfg(target_endian = "big")]
+/// assert_eq!(*result, 0x1020304);
+///
+/// # Some(()) }
+/// # test().ok_or(EINVAL)?;
+/// # Ok::<(), Error>(())
+/// ```
+///
 /// # Safety
 ///
 /// All bit-patterns must be valid for this type. This type must not have interior mutability.
-pub unsafe trait FromBytes {}
+pub unsafe trait FromBytes {
+    /// Converts a slice of bytes to a reference to `Self`.
+    ///
+    /// Succeeds if the reference is properly aligned, and the size of `bytes` is equal to that of
+    /// `T` and different from zero.
+    ///
+    /// Otherwise, returns [`None`].
+    fn from_bytes(bytes: &[u8]) -> Option<&Self>
+    where
+        Self: Sized,
+    {
+        let slice_ptr = bytes.as_ptr().cast::<Self>();
+        let size = size_of::<Self>();
+
+        #[allow(clippy::incompatible_msrv)]
+        if bytes.len() == size && slice_ptr.is_aligned() {
+            // SAFETY: Size and alignment were just checked.
+            unsafe { Some(&*slice_ptr) }
+        } else {
+            None
+        }
+    }
+
+    /// Converts a mutable slice of bytes to a reference to `Self`.
+    ///
+    /// Succeeds if the reference is properly aligned, and the size of `bytes` is equal to that of
+    /// `T` and different from zero.
+    ///
+    /// Otherwise, returns [`None`].
+    fn from_bytes_mut(bytes: &mut [u8]) -> Option<&mut Self>
+    where
+        Self: AsBytes + Sized,
+    {
+        let slice_ptr = bytes.as_mut_ptr().cast::<Self>();
+        let size = size_of::<Self>();
+
+        #[allow(clippy::incompatible_msrv)]
+        if bytes.len() == size && slice_ptr.is_aligned() {
+            // SAFETY: Size and alignment were just checked.
+            unsafe { Some(&mut *slice_ptr) }
+        } else {
+            None
+        }
+    }
+
+    /// Creates an owned instance of `Self` by copying `bytes`.
+    ///
+    /// Unlike [`FromBytes::from_bytes`], which requires aligned input, this method can be used on
+    /// non-aligned data at the cost of a copy.
+    fn from_bytes_copy(bytes: &[u8]) -> Option<Self>
+    where
+        Self: Sized,
+    {
+        if bytes.len() == size_of::<Self>() {
+            // SAFETY: we just verified that `bytes` has the same size as `Self`, and per the
+            // invariants of `FromBytes`, any byte sequence of the correct length is a valid value
+            // for `Self`.
+            Some(unsafe { core::ptr::read_unaligned(bytes.as_ptr().cast::<Self>()) })
+        } else {
+            None
+        }
+    }
+}
 
 macro_rules! impl_frombytes {
     ($($({$($generics:tt)*})? $t:ty, )*) => {
@@ -47,7 +132,32 @@ impl_frombytes! {
 ///
 /// Values of this type may not contain any uninitialized bytes. This type must not have interior
 /// mutability.
-pub unsafe trait AsBytes {}
+pub unsafe trait AsBytes {
+    /// Returns `self` as a slice of bytes.
+    fn as_bytes(&self) -> &[u8] {
+        // CAST: `Self` implements `AsBytes` thus all bytes of `self` are initialized.
+        let data = core::ptr::from_ref(self).cast::<u8>();
+        let len = core::mem::size_of_val(self);
+
+        // SAFETY: `data` is non-null and valid for reads of `len * sizeof::<u8>()` bytes.
+        unsafe { core::slice::from_raw_parts(data, len) }
+    }
+
+    /// Returns `self` as a mutable slice of bytes.
+    fn as_bytes_mut(&mut self) -> &mut [u8]
+    where
+        Self: FromBytes,
+    {
+        // CAST: `Self` implements both `AsBytes` and `FromBytes` thus making `Self`
+        // bi-directionally transmutable to `[u8; size_of_val(self)]`.
+        let data = core::ptr::from_mut(self).cast::<u8>();
+        let len = core::mem::size_of_val(self);
+
+        // SAFETY: `data` is non-null and valid for read and writes of `len * sizeof::<u8>()`
+        // bytes.
+        unsafe { core::slice::from_raw_parts_mut(data, len) }
+    }
+}
 
 macro_rules! impl_asbytes {
     ($($({$($generics:tt)*})? $t:ty, )*) => {