[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20250711040947.1252162-2-fujita.tomonori@gmail.com>
Date: Fri, 11 Jul 2025 13:09:45 +0900
From: FUJITA Tomonori <fujita.tomonori@...il.com>
To: alex.gaynor@...il.com,
dakr@...nel.org,
gregkh@...uxfoundation.org,
ojeda@...nel.org,
rafael@...nel.org,
robh@...nel.org,
saravanak@...gle.com,
tmgross@...ch.edu
Cc: a.hindborg@...nel.org,
aliceryhl@...gle.com,
bhelgaas@...gle.com,
bjorn3_gh@...tonmail.com,
boqun.feng@...il.com,
david.m.ertman@...el.com,
devicetree@...r.kernel.org,
gary@...yguo.net,
ira.weiny@...el.com,
kwilczynski@...nel.org,
lenb@...nel.org,
leon@...nel.org,
linux-acpi@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-pci@...r.kernel.org,
lossin@...nel.org,
netdev@...r.kernel.org,
rust-for-linux@...r.kernel.org
Subject: [PATCH v4 1/3] rust: device_id: split out index support into a separate trait
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 the RawDeviceId trait.
The changes to acpi.rs and driver.rs were made by Danilo.
Acked-by: Danilo Krummrich <dakr@...nel.org>
Reviewed-by: Trevor Gross <tmgross@...ch.edu>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@...il.com>
---
rust/kernel/acpi.rs | 15 ++++---
rust/kernel/auxiliary.rs | 11 ++---
rust/kernel/device_id.rs | 91 +++++++++++++++++++++++++++++-----------
rust/kernel/driver.rs | 8 +++-
rust/kernel/of.rs | 15 ++++---
rust/kernel/pci.rs | 11 ++---
6 files changed, 104 insertions(+), 47 deletions(-)
diff --git a/rust/kernel/acpi.rs b/rust/kernel/acpi.rs
index 2af4d4f92924..7ae317368b00 100644
--- a/rust/kernel/acpi.rs
+++ b/rust/kernel/acpi.rs
@@ -2,7 +2,11 @@
//! Advanced Configuration and Power Interface abstractions.
-use crate::{bindings, device_id::RawDeviceId, prelude::*};
+use crate::{
+ bindings,
+ device_id::{RawDeviceId, RawDeviceIdIndex},
+ prelude::*,
+};
/// IdTable type for ACPI drivers.
pub type IdTable<T> = &'static dyn kernel::device_id::IdTable<DeviceId, T>;
@@ -12,13 +16,14 @@
#[derive(Clone, Copy)]
pub struct DeviceId(bindings::acpi_device_id);
-// SAFETY:
-// * `DeviceId` is a `#[repr(transparent)` wrapper of `struct acpi_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.
+// SAFETY: `DeviceId` is a `#[repr(transparent)]` wrapper of `acpi_device_id` and does not add
+// additional invariants, so it's safe to transmute to `RawType`.
unsafe impl RawDeviceId for DeviceId {
type RawType = bindings::acpi_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::acpi_device_id, driver_data);
fn index(&self) -> usize {
diff --git a/rust/kernel/auxiliary.rs b/rust/kernel/auxiliary.rs
index 2985673181b7..12a4d36dc452 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::{from_result, to_result, Result},
prelude::*,
@@ -134,13 +134,14 @@ 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.
+// 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`.
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 0a4eb56d98f2..8ed2c946144c 100644
--- a/rust/kernel/device_id.rs
+++ b/rust/kernel/device_id.rs
@@ -14,32 +14,41 @@
///
/// # Safety
///
-/// Implementers must ensure that:
-/// - `Self` is layout-compatible with [`RawDeviceId::RawType`]; i.e. it's safe to transmute to
-/// `RawDeviceId`.
+/// 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.
+/// 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.
+/// 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.
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 be added during `Self` to `RawType` conversion,
+/// but there's currently no way to do it when using traits in const.
+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 +77,15 @@ 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
+ ///
+ /// `data_offset` as `None` is always safe.
+ /// If `data_offset` is `Some(data_offset)`, then:
+ /// - `data_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 `data_offset` must be correctly sized to hold a `usize`.
+ const unsafe fn build(ids: [(T, U); N], data_offset: Option<usize>) -> Self {
let mut raw_ids = [const { MaybeUninit::<T::RawType>::uninit() }; N];
let mut infos = [const { MaybeUninit::uninit() }; N];
@@ -77,14 +94,16 @@ 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_offset(T::DRIVER_DATA_OFFSET as _)
- .cast::<usize>()
- .write(i);
+ if let Some(data_offset) = data_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_offset(data_offset as _)
+ .cast::<usize>()
+ .write(i);
+ }
}
// SAFETY: this is effectively a move: `infos[i] = ids[i].1`. We make a copy here but
@@ -109,12 +128,34 @@ 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.
+ /// If the device implements [`RawDeviceIdIndex`], consider using [`IdArray::new`] instead.
+ 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/driver.rs b/rust/kernel/driver.rs
index f8dd7593e8dc..a8f2675ba7a7 100644
--- a/rust/kernel/driver.rs
+++ b/rust/kernel/driver.rs
@@ -170,7 +170,7 @@ fn acpi_id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
// and does not add additional invariants, so it's safe to transmute.
let id = unsafe { &*raw_id.cast::<acpi::DeviceId>() };
- Some(table.info(<acpi::DeviceId as crate::device_id::RawDeviceId>::index(id)))
+ Some(table.info(<acpi::DeviceId as crate::device_id::RawDeviceIdIndex>::index(id)))
}
}
}
@@ -204,7 +204,11 @@ fn of_id_info(dev: &device::Device) -> Option<&'static Self::IdInfo> {
// and does not add additional invariants, so it's safe to transmute.
let id = unsafe { &*raw_id.cast::<of::DeviceId>() };
- Some(table.info(<of::DeviceId as crate::device_id::RawDeviceId>::index(id)))
+ Some(
+ table.info(<of::DeviceId as crate::device_id::RawDeviceIdIndex>::index(
+ id,
+ )),
+ )
}
}
}
diff --git a/rust/kernel/of.rs b/rust/kernel/of.rs
index 52fe0c77b9a1..0888469bddb7 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>;
@@ -12,13 +16,14 @@
#[derive(Clone, Copy)]
pub struct DeviceId(bindings::of_device_id);
-// 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.
+// 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`.
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 8b884e324dcf..ba9a5c6fc513 100644
--- a/rust/kernel/pci.rs
+++ b/rust/kernel/pci.rs
@@ -6,7 +6,7 @@
use crate::{
bindings, container_of, device,
- device_id::RawDeviceId,
+ device_id::{RawDeviceId, RawDeviceIdIndex},
devres::Devres,
driver,
error::{from_result, to_result, Result},
@@ -159,13 +159,14 @@ 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.
+// 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`.
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
Powered by blists - more mailing lists