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[180.34.120.7]) by smtp.gmail.com with ESMTPSA id d9443c01a7336-23acb3b8324sm107240885ad.178.2025.07.01.07.14.23 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 01 Jul 2025 07:14:27 -0700 (PDT) From: FUJITA Tomonori To: alex.gaynor@gmail.com, dakr@kernel.org, gregkh@linuxfoundation.org, ojeda@kernel.org, rafael@kernel.org, robh@kernel.org, saravanak@google.com Cc: a.hindborg@kernel.org, aliceryhl@google.com, bhelgaas@google.com, bjorn3_gh@protonmail.com, boqun.feng@gmail.com, david.m.ertman@intel.com, devicetree@vger.kernel.org, gary@garyguo.net, ira.weiny@intel.com, kwilczynski@kernel.org, leon@kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, lossin@kernel.org, netdev@vger.kernel.org, rust-for-linux@vger.kernel.org, tmgross@umich.edu Subject: [PATCH v2 1/3] rust: device_id: split out index support into a separate trait Date: Tue, 1 Jul 2025 23:12:50 +0900 Message-ID: <20250701141252.600113-2-fujita.tomonori@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20250701141252.600113-1-fujita.tomonori@gmail.com> References: <20250701141252.600113-1-fujita.tomonori@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 --- 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 @@ =20 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: &'stat= ic CStr) -> Self { // SAFETY: // * `DeviceId` is a `#[repr(transparent)`] wrapper of `auxiliary_device_i= d` 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 =3D bindings::auxiliary_device_id; +} =20 +// SAFETY: +// * `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field. +unsafe impl RawDeviceIdIndex for DeviceId { const DRIVER_DATA_OFFSET: usize =3D core::mem::offset_of!(bindings::auxiliary_device_id, driver_data); =20 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_i= mpl` unstable feature, /// which is broken/gone in Rust 1.73. -/// -/// - `DRIVER_DATA_OFFSET` is the offset of context/data field of the de= vice ID (usually named -/// `driver_data`) of the device ID, the field is suitable sized to wr= ite a `usize` value. -/// -/// Similar to the previous requirement, the data should ideally be ad= ded during `Self` to -/// `RawType` conversion, but there's currently no way to do it when u= sing 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; +} =20 - /// 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 conte= xt/data field (e.g., the +/// `driver_data` field) within the raw device ID structure. This fiel= d must be correctly sized +/// to hold a `usize`. +/// +/// Ideally, the data should ideally be added during `Self` to `RawTyp= e` 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 sp= ecified +/// 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; =20 - /// 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; } =20 @@ -68,7 +82,14 @@ impl IdArray= { /// Creates a new instance of the array. /// /// The contents are derived from the given identifiers and context in= formation. - 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/da= ta field + /// (e.g., the `driver_data` field) within the raw device ID structu= re. + /// - The field at `offset` must be correctly sized to hold a `usize`. + const unsafe fn build(ids: [(T, U); N], offset: Option) -> Self= { let mut raw_ids =3D [const { MaybeUninit::::uninit() }= ; N]; let mut infos =3D [const { MaybeUninit::uninit() }; N]; =20 @@ -77,14 +98,17 @@ impl IdArray { // SAFETY: by the safety requirement of `RawDeviceId`, we're g= uaranteed that `T` is // layout-wise compatible with `RawType`. raw_ids[i] =3D unsafe { core::mem::transmute_copy(&ids[i].0) }; - // SAFETY: by the safety requirement of `RawDeviceId`, this wo= uld be effectively - // `raw_ids[i].driver_data =3D i;`. - unsafe { - raw_ids[i] - .as_mut_ptr() - .byte_add(T::DRIVER_DATA_OFFSET) - .cast::() - .write(i); + + if let Some(offset) =3D offset { + // SAFETY: by the safety requirement of this function, thi= s would be effectively + // `raw_ids[i].driver_data =3D i;`. + unsafe { + raw_ids[i] + .as_mut_ptr() + .byte_add(offset) + .cast::() + .write(i); + } } =20 // SAFETY: this is effectively a move: `infos[i] =3D ids[i].1`= . We make a copy here but @@ -92,7 +116,6 @@ impl IdArray= { infos[i] =3D MaybeUninit::new(unsafe { core::ptr::read(&ids[i]= .1) }); i +=3D 1; } - core::mem::forget(ids); =20 Self { @@ -109,12 +132,33 @@ impl IdArray { } } =20 + /// Creates a new instance of the array without writing index values. + /// + /// The contents are derived from the given identifiers and context in= formation. + pub const fn new_without_index(ids: [(T, U); N]) -> Self { + // SAFETY: Calling `Self::build` with `offset =3D 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 { &self.raw_ids } } =20 +impl IdArray { + /// Creates a new instance of the array. + /// + /// The contents are derived from the given identifiers and context in= formation. + 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 @@ =20 //! Device Tree / Open Firmware abstractions. =20 -use crate::{bindings, device_id::RawDeviceId, prelude::*}; +use crate::{ + bindings, + device_id::{RawDeviceId, RawDeviceIdIndex}, + prelude::*, +}; =20 /// IdTable type for OF drivers. pub type IdTable =3D &'static dyn kernel::device_id::IdTable; @@ -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 =3D bindings::of_device_id; +} =20 +// SAFETY: +// * `DRIVER_DATA_OFFSET` is the offset to the `data` field. +unsafe impl RawDeviceIdIndex for DeviceId { const DRIVER_DATA_OFFSET: usize =3D core::mem::offset_of!(bindings::of= _device_id, data); =20 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 =3D bindings::pci_device_id; +} =20 +// SAFETY: +// * `DRIVER_DATA_OFFSET` is the offset to the `driver_data` field. +unsafe impl RawDeviceIdIndex for DeviceId { const DRIVER_DATA_OFFSET: usize =3D core::mem::offset_of!(bindings::pc= i_device_id, driver_data); =20 fn index(&self) -> usize { --=20 2.43.0