[PATCH v2 0/3] rust: Build PHY device tables by using module_device_table macro

[PATCH v2 0/3] rust: Build PHY device tables by using module_device_table macro

[FUJITA Tomonori]

Build PHY device tables by using module_device_table macro.

The PHY abstractions have been generating their own device tables
manually instead of using the module_device_table macro provided by
the device_id crate. However, the format of device tables occasionally
changes [1] [2], requiring updates to both the device_id crate and the custom
format used by the PHY abstractions, which is cumbersome to maintain.

[1]: https://lore.kernel.org/lkml/20241119235705.1576946-14-masahiroy@kernel.org/
[2]: https://lore.kernel.org/lkml/6e2f70b07a710e761eb68d089d96cee7b27bb2d5.1750511018.git.legion@kernel.org/

v2:
- Split off index-related parts of RawDeviceId into RawDeviceIdIndex
v1: https://lore.kernel.org/lkml/20250623060951.118564-1-fujita.tomonori@gmail.com/

FUJITA Tomonori (3):
  rust: device_id: split out index support into a separate trait
  rust: net::phy represent DeviceId as transparent wrapper over
    mdio_device_id
  rust: net::phy Change module_phy_driver macro to use
    module_device_table macro

 rust/kernel/auxiliary.rs |   7 ++-
 rust/kernel/device_id.rs |  80 +++++++++++++++++++++++-------
 rust/kernel/net/phy.rs   | 104 +++++++++++++++++++--------------------
 rust/kernel/of.rs        |  11 ++++-
 rust/kernel/pci.rs       |   7 ++-
 5 files changed, 132 insertions(+), 77 deletions(-)


base-commit: 769e324b66b0d92d04f315d0c45a0f72737c7494
-- 
2.43.0

[PATCH v2 1/3] rust: device_id: split out index support into a separate trait

[FUJITA Tomonori]

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.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 rust/kernel/auxiliary.rs |  7 +++-
 rust/kernel/device_id.rs | 80 +++++++++++++++++++++++++++++++---------
 rust/kernel/of.rs        | 11 +++++-
 rust/kernel/pci.rs       |  7 +++-
 4 files changed, 81 insertions(+), 24 deletions(-)

diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs
index d2cfe1eeefb6..655ed61247d0 100644
--- a/rust/kernel/auxiliary.rs
+++ b/rust/kernel/auxiliary.rs
@@ -6,7 +6,7 @@
 
 use crate::{
     bindings, container_of, device,
-    device_id::RawDeviceId,
+    device_id::{RawDeviceId, RawDeviceIdIndex},
     driver,
     error::{to_result, Result},
     prelude::*,
@@ -143,10 +143,13 @@ pub const fn new(modname: &'static CStr, name: &'static CStr) -> Self {
 // SAFETY:
 // * `DeviceId` is a `#[repr(transparent)`] wrapper of `auxiliary_device_id` and does not add
 //   additional invariants, so it's safe to transmute to `RawType`.
-// * `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field.
 unsafe impl RawDeviceId for DeviceId {
     type RawType = bindings::auxiliary_device_id;
+}
 
+// SAFETY:
+// * `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field.
+unsafe impl RawDeviceIdIndex for DeviceId {
     const DRIVER_DATA_OFFSET: usize =
         core::mem::offset_of!(bindings::auxiliary_device_id, driver_data);
 
diff --git a/rust/kernel/device_id.rs b/rust/kernel/device_id.rs
index 3dc72ca8cfc2..3bcab2310087 100644
--- a/rust/kernel/device_id.rs
+++ b/rust/kernel/device_id.rs
@@ -24,22 +24,36 @@
 ///     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.
+/// Extension trait for [`RawDeviceId`] for devices that embed an index or context value.
+///
+/// This is typically used when the device ID struct includes a field like `driver_data`
+/// that is used to store a pointer-sized value (e.g., an index or context pointer).
+///
+/// # Safety
+///
+/// Implementers must ensure that:
+///   - `DRIVER_DATA_OFFSET` is the correct offset (in bytes) to the context/data field (e.g., the
+///     `driver_data` field) within the raw device ID structure. This field must be correctly sized
+///     to hold a `usize`.
+///
+///     Ideally, 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.
+///
+///   - The `index` method must return the value stored at the location specified
+///     by `DRIVER_DATA_OFFSET`, assuming `self` is layout-compatible with `RawType`.
+pub unsafe trait RawDeviceIdIndex: RawDeviceId {
+    /// The offset (in bytes) to the context/data field in the raw device ID.
     const DRIVER_DATA_OFFSET: usize;
 
-    /// The index stored at `DRIVER_DATA_OFFSET` of the implementor of the [`RawDeviceId`] trait.
+    /// The index stored at `DRIVER_DATA_OFFSET` of the implementor of the [`RawDeviceIdIndex`]
+    /// trait.
     fn index(&self) -> usize;
 }
 
@@ -68,7 +82,14 @@ 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 {
         let mut raw_ids = [const { MaybeUninit::<T::RawType>::uninit() }; N];
         let mut infos = [const { MaybeUninit::uninit() }; N];
 
@@ -77,14 +98,17 @@ impl<T: RawDeviceId, U, const N: usize> IdArray<T, U, 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_add(T::DRIVER_DATA_OFFSET)
-                    .cast::<usize>()
-                    .write(i);
+
+            if let Some(offset) = offset {
+                // SAFETY: by the safety requirement of this function, this would be effectively
+                // `raw_ids[i].driver_data = i;`.
+                unsafe {
+                    raw_ids[i]
+                        .as_mut_ptr()
+                        .byte_add(offset)
+                        .cast::<usize>()
+                        .write(i);
+                }
             }
 
             // SAFETY: this is effectively a move: `infos[i] = ids[i].1`. We make a copy here but
@@ -92,7 +116,6 @@ 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);
 
         Self {
@@ -109,12 +132,33 @@ 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.
+    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) }
+    }
+
     /// Reference to the contained [`RawIdArray`].
     pub const fn raw_ids(&self) -> &RawIdArray<T, N> {
         &self.raw_ids
     }
 }
 
+impl<T: RawDeviceId + RawDeviceIdIndex, 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: by the safety requirement of `RawDeviceIdIndex`,
+        // `T::DRIVER_DATA_OFFSET` is guaranteed to be the correct offset (in bytes) to
+        // a field within `T::RawType`.
+        unsafe { Self::build(ids, Some(T::DRIVER_DATA_OFFSET)) }
+    }
+}
+
 /// A device id table.
 ///
 /// This trait is only implemented by `IdArray`.
diff --git a/rust/kernel/of.rs b/rust/kernel/of.rs
index 40d1bd13682c..c690bceb0d73 100644
--- a/rust/kernel/of.rs
+++ b/rust/kernel/of.rs
@@ -2,7 +2,11 @@
 
 //! Device Tree / Open Firmware abstractions.
 
-use crate::{bindings, device_id::RawDeviceId, prelude::*};
+use crate::{
+    bindings,
+    device_id::{RawDeviceId, RawDeviceIdIndex},
+    prelude::*,
+};
 
 /// IdTable type for OF drivers.
 pub type IdTable<T> = &'static dyn kernel::device_id::IdTable<DeviceId, T>;
@@ -15,10 +19,13 @@
 // SAFETY:
 // * `DeviceId` is a `#[repr(transparent)` wrapper of `struct of_device_id` and does not add
 //   additional invariants, so it's safe to transmute to `RawType`.
-// * `DRIVER_DATA_OFFSET` is the offset to the `data` field.
 unsafe impl RawDeviceId for DeviceId {
     type RawType = bindings::of_device_id;
+}
 
+// SAFETY:
+// * `DRIVER_DATA_OFFSET` is the offset to the `data` field.
+unsafe impl RawDeviceIdIndex for DeviceId {
     const DRIVER_DATA_OFFSET: usize = core::mem::offset_of!(bindings::of_device_id, data);
 
     fn index(&self) -> usize {
diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
index 6b94fd7a3ce9..96d6275c7afb 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -7,7 +7,7 @@
 use crate::{
     alloc::flags::*,
     bindings, container_of, device,
-    device_id::RawDeviceId,
+    device_id::{RawDeviceId, RawDeviceIdIndex},
     devres::Devres,
     driver,
     error::{to_result, Result},
@@ -164,10 +164,13 @@ pub const fn from_class(class: u32, class_mask: u32) -> Self {
 // SAFETY:
 // * `DeviceId` is a `#[repr(transparent)` wrapper of `pci_device_id` and does not add
 //   additional invariants, so it's safe to transmute to `RawType`.
-// * `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field.
 unsafe impl RawDeviceId for DeviceId {
     type RawType = bindings::pci_device_id;
+}
 
+// SAFETY:
+// * `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field.
+unsafe impl RawDeviceIdIndex for DeviceId {
     const DRIVER_DATA_OFFSET: usize = core::mem::offset_of!(bindings::pci_device_id, driver_data);
 
     fn index(&self) -> usize {
-- 
2.43.0

[PATCH v2 2/3] rust: net::phy represent DeviceId as transparent wrapper over mdio_device_id

[FUJITA Tomonori]

Refactor the DeviceId struct to be a #[repr(transparent)] wrapper
around the C struct bindings::mdio_device_id.

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

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 rust/kernel/net/phy.rs | 53 +++++++++++++++++++++---------------------
 1 file changed, 27 insertions(+), 26 deletions(-)

diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
index 65ac4d59ad77..940972ffadae 100644
--- a/rust/kernel/net/phy.rs
+++ b/rust/kernel/net/phy.rs
@@ -507,7 +507,7 @@ pub const fn create_phy_driver<T: Driver>() -> DriverVTable {
     DriverVTable(Opaque::new(bindings::phy_driver {
         name: T::NAME.as_char_ptr().cast_mut(),
         flags: T::FLAGS,
-        phy_id: T::PHY_DEVICE_ID.id,
+        phy_id: T::PHY_DEVICE_ID.id(),
         phy_id_mask: T::PHY_DEVICE_ID.mask_as_int(),
         soft_reset: if T::HAS_SOFT_RESET {
             Some(Adapter::<T>::soft_reset_callback)
@@ -691,42 +691,41 @@ fn drop(&mut self) {
 ///
 /// Represents the kernel's `struct mdio_device_id`. This is used to find an appropriate
 /// PHY driver.
-pub struct DeviceId {
-    id: u32,
-    mask: DeviceMask,
-}
+#[repr(transparent)]
+#[derive(Clone, Copy)]
+pub struct DeviceId(bindings::mdio_device_id);
 
 impl DeviceId {
     /// Creates a new instance with the exact match mask.
     pub const fn new_with_exact_mask(id: u32) -> Self {
-        DeviceId {
-            id,
-            mask: DeviceMask::Exact,
-        }
+        Self(bindings::mdio_device_id {
+            phy_id: id,
+            phy_id_mask: DeviceMask::Exact.as_int(),
+        })
     }
 
     /// Creates a new instance with the model match mask.
     pub const fn new_with_model_mask(id: u32) -> Self {
-        DeviceId {
-            id,
-            mask: DeviceMask::Model,
-        }
+        Self(bindings::mdio_device_id {
+            phy_id: id,
+            phy_id_mask: DeviceMask::Model.as_int(),
+        })
     }
 
     /// Creates a new instance with the vendor match mask.
     pub const fn new_with_vendor_mask(id: u32) -> Self {
-        DeviceId {
-            id,
-            mask: DeviceMask::Vendor,
-        }
+        Self(bindings::mdio_device_id {
+            phy_id: id,
+            phy_id_mask: DeviceMask::Vendor.as_int(),
+        })
     }
 
     /// Creates a new instance with a custom match mask.
     pub const fn new_with_custom_mask(id: u32, mask: u32) -> Self {
-        DeviceId {
-            id,
-            mask: DeviceMask::Custom(mask),
-        }
+        Self(bindings::mdio_device_id {
+            phy_id: id,
+            phy_id_mask: DeviceMask::Custom(mask).as_int(),
+        })
     }
 
     /// Creates a new instance from [`Driver`].
@@ -734,18 +733,20 @@ pub const fn new_with_driver<T: Driver>() -> Self {
         T::PHY_DEVICE_ID
     }
 
+    /// Get a `phy_id` as u32.
+    pub const fn id(&self) -> u32 {
+        self.0.phy_id
+    }
+
     /// Get a `mask` as u32.
     pub const fn mask_as_int(&self) -> u32 {
-        self.mask.as_int()
+        self.0.phy_id_mask
     }
 
     // macro use only
     #[doc(hidden)]
     pub const fn mdio_device_id(&self) -> bindings::mdio_device_id {
-        bindings::mdio_device_id {
-            phy_id: self.id,
-            phy_id_mask: self.mask.as_int(),
-        }
+        self.0
     }
 }
 
-- 
2.43.0

[PATCH v2 3/3] rust: net::phy Change module_phy_driver macro to use module_device_table macro

[FUJITA Tomonori]

Change module_phy_driver macro to build device tables which are
exported to userspace by using module_device_table macro.

Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
---
 rust/kernel/net/phy.rs | 51 ++++++++++++++++++++----------------------
 1 file changed, 24 insertions(+), 27 deletions(-)

diff --git a/rust/kernel/net/phy.rs b/rust/kernel/net/phy.rs
index 940972ffadae..8bb362aefe27 100644
--- a/rust/kernel/net/phy.rs
+++ b/rust/kernel/net/phy.rs
@@ -6,7 +6,7 @@
 //!
 //! C headers: [`include/linux/phy.h`](srctree/include/linux/phy.h).
 
-use crate::{error::*, prelude::*, types::Opaque};
+use crate::{device_id::RawDeviceId, error::*, prelude::*, types::Opaque};
 use core::{marker::PhantomData, ptr::addr_of_mut};
 
 pub mod reg;
@@ -750,6 +750,12 @@ pub const fn mdio_device_id(&self) -> bindings::mdio_device_id {
     }
 }
 
+// SAFETY: [`DeviceId`] is a `#[repr(transparent)` wrapper of `struct mdio_device_id`
+// and does not add additional invariants, so it's safe to transmute to `RawType`.
+unsafe impl RawDeviceId for DeviceId {
+    type RawType = bindings::mdio_device_id;
+}
+
 enum DeviceMask {
     Exact,
     Model,
@@ -850,19 +856,18 @@ const fn as_int(&self) -> u32 {
 ///     }
 /// };
 ///
-/// const _DEVICE_TABLE: [::kernel::bindings::mdio_device_id; 2] = [
-///     ::kernel::bindings::mdio_device_id {
-///         phy_id: 0x00000001,
-///         phy_id_mask: 0xffffffff,
-///     },
-///     ::kernel::bindings::mdio_device_id {
-///         phy_id: 0,
-///         phy_id_mask: 0,
-///     },
-/// ];
-/// #[cfg(MODULE)]
-/// #[no_mangle]
-/// static __mod_device_table__mdio__phydev: [::kernel::bindings::mdio_device_id; 2] = _DEVICE_TABLE;
+/// const N: usize = 1;
+///
+/// const TABLE: ::kernel::device_id::IdArray<::kernel::net::phy::DeviceId, (), N> =
+///     ::kernel::device_id::IdArray::new_without_index([
+///         ::kernel::net::phy::DeviceId(
+///             ::kernel::bindings::mdio_device_id {
+///                 phy_id: 0x00000001,
+///                 phy_id_mask: 0xffffffff,
+///             }),
+///     ]);
+///
+/// ::kernel::module_device_table!("mdio", phydev, TABLE);
 /// ```
 #[macro_export]
 macro_rules! module_phy_driver {
@@ -873,20 +878,12 @@ macro_rules! module_phy_driver {
     };
 
     (@device_table [$($dev:expr),+]) => {
-        // SAFETY: C will not read off the end of this constant since the last element is zero.
-        const _DEVICE_TABLE: [$crate::bindings::mdio_device_id;
-            $crate::module_phy_driver!(@count_devices $($dev),+) + 1] = [
-            $($dev.mdio_device_id()),+,
-            $crate::bindings::mdio_device_id {
-                phy_id: 0,
-                phy_id_mask: 0
-            }
-        ];
+        const N: usize = $crate::module_phy_driver!(@count_devices $($dev),+);
+
+        const TABLE: $crate::device_id::IdArray<$crate::net::phy::DeviceId, (), N> =
+            $crate::device_id::IdArray::new_without_index([ $(($dev,())),+, ]);
 
-        #[cfg(MODULE)]
-        #[no_mangle]
-        static __mod_device_table__mdio__phydev: [$crate::bindings::mdio_device_id;
-            $crate::module_phy_driver!(@count_devices $($dev),+) + 1] = _DEVICE_TABLE;
+        $crate::module_device_table!("mdio", phydev, TABLE);
     };
 
     (drivers: [$($driver:ident),+ $(,)?], device_table: [$($dev:expr),+ $(,)?], $($f:tt)*) => {
-- 
2.43.0

Re: [PATCH v2 1/3] rust: device_id: split out index support into a separate trait

[Danilo Krummrich]

On Tue, Jul 01, 2025 at 11:12:50PM +0900, FUJITA Tomonori wrote:
> +// SAFETY:
> +// * `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field.

Here and for a few other occurances, this doesn't need to be a list, since it's
just a single item.

> +/// Extension trait for [`RawDeviceId`] for devices that embed an index or context value.
> +///
> +/// This is typically used when the device ID struct includes a field like `driver_data`
> +/// that is used to store a pointer-sized value (e.g., an index or context pointer).
> +///
> +/// # Safety
> +///
> +/// Implementers must ensure that:
> +///   - `DRIVER_DATA_OFFSET` is the correct offset (in bytes) to the context/data field (e.g., the
> +///     `driver_data` field) within the raw device ID structure. This field must be correctly sized
> +///     to hold a `usize`.
> +///
> +///     Ideally, the data should ideally be added during `Self` to `RawType` conversion,

Remove one of the duplicate "ideally".

> +///     but there's currently no way to do it when using traits in const.
> +///
> +///   - The `index` method must return the value stored at the location specified
> +///     by `DRIVER_DATA_OFFSET`, assuming `self` is layout-compatible with `RawType`.

I think technically this safety requirement isn't needed.

With this:

	Acked-by: Danilo Krummrich <dakr@kernel.org>

Re: [PATCH v2 1/3] rust: device_id: split out index support into a separate trait

[FUJITA Tomonori]

On Fri, 4 Jul 2025 02:44:57 +0200
Danilo Krummrich <dakr@kernel.org> wrote:

> On Tue, Jul 01, 2025 at 11:12:50PM +0900, FUJITA Tomonori wrote:
>> +// SAFETY:
>> +// * `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field.
> 
> Here and for a few other occurances, this doesn't need to be a list, since it's
> just a single item.

Indeed, fixed all the places.


>> +/// Extension trait for [`RawDeviceId`] for devices that embed an index or context value.
>> +///
>> +/// This is typically used when the device ID struct includes a field like `driver_data`
>> +/// that is used to store a pointer-sized value (e.g., an index or context pointer).
>> +///
>> +/// # Safety
>> +///
>> +/// Implementers must ensure that:
>> +///   - `DRIVER_DATA_OFFSET` is the correct offset (in bytes) to the context/data field (e.g., the
>> +///     `driver_data` field) within the raw device ID structure. This field must be correctly sized
>> +///     to hold a `usize`.
>> +///
>> +///     Ideally, the data should ideally be added during `Self` to `RawType` conversion,
> 
> Remove one of the duplicate "ideally".

Oops, removed.


>> +///     but there's currently no way to do it when using traits in const.
>> +///
>> +///   - The `index` method must return the value stored at the location specified
>> +///     by `DRIVER_DATA_OFFSET`, assuming `self` is layout-compatible with `RawType`.
> 
> I think technically this safety requirement isn't needed.

Ah, you're right. I'll remove it.


> With this:
> 
> 	Acked-by: Danilo Krummrich <dakr@kernel.org>

Thanks a lot!