On Tue, 08 Jul 2025 23:10:48 -0400
"Trevor Gross" [off-list ref] wrote:

On Fri Jul 4, 2025 at 12:10 AM EDT, FUJITA Tomonori wrote:

quoted

Introduce a new trait `RawDeviceIdIndex`, which extends `RawDeviceId`
to provide support for device ID types that include an index or
context field (e.g., `driver_data`). This separates the concerns of
layout compatibility and index-based data embedding, and allows
`RawDeviceId` to be implemented for types that do not contain a
`driver_data` field. Several such structures are defined in
include/linux/mod_devicetable.h.

Refactor `IdArray::new()` into a generic `build()` function, which
takes an optional offset. Based on the presence of `RawDeviceIdIndex`,
index writing is conditionally enabled. A new `new_without_index()`
constructor is also provided for use cases where no index should be
written.

This refactoring is a preparation for enabling the PHY abstractions to
use device_id trait.

Acked-by: Danilo Krummrich <dakr@kernel.org>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 rust/kernel/auxiliary.rs | 11 ++---
 rust/kernel/device_id.rs | 91 ++++++++++++++++++++++++++++------------
 rust/kernel/of.rs        | 15 ++++---
 rust/kernel/pci.rs       | 11 ++---
 4 files changed, 87 insertions(+), 41 deletions(-)

Few small suggestions if you wind up spinning this again:

quoted

diff --git a/rust/kernel/device_id.rs b/rust/kernel/device_id.rs

[...]

@@ -68,7 +77,14 @@ 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 {
+    ///
+    /// # Safety
+    ///
+    /// If `offset` is `Some(offset)`, then:
+    /// - `offset` must be the correct offset (in bytes) to the context/data field
+    ///   (e.g., the `driver_data` field) within the raw device ID structure.
+    /// - The field at `offset` must be correctly sized to hold a `usize`.
+    const unsafe fn build(ids: [(T, U); N], offset: Option<usize>) -> Self {

Could you mention that calling with `offset` as `None` is always safe?

Indeed, added.

Also calling the arg `data_offset` might be more clear.

Yeah, changed.

quoted

@@ -92,7 +111,6 @@ impl<T: RawDeviceId, U, const N: usize> IdArray<T, U, N> {
             infos[i] = MaybeUninit::new(unsafe { core::ptr::read(&ids[i].1) });
             i += 1;
         }
-
         core::mem::forget(ids);

This removes the space between a block and an expression, possibly
unintentional? :)

Oops, unintentional. Dropped the change.

quoted

@@ -109,12 +127,33 @@ impl<T: RawDeviceId, U, const N: usize> IdArray<T, U, N> {
         }
     }
 
+    /// Creates a new instance of the array without writing index values.
+    ///
+    /// The contents are derived from the given identifiers and context information.

Maybe the docs here should crosslink:

    If the device implements [`RawDeviceIdIndex`], consider using
    [`new`] instead.

Looks nice, added. [`new`] doesn't work so I use [`IdArray::new`].

quoted

+    pub const fn new_without_index(ids: [(T, U); N]) -> Self {
+        // SAFETY: Calling `Self::build` with `offset = None` is always safe,
+        // because no raw memory writes are performed in this case.
+        unsafe { Self::build(ids, None) }
+    }
+

With those changes, or as-is if there winds up not being another
version:

Reviewed-by: Trevor Gross <tmgross@umich.edu>

Thanks!