From patchwork Thu Dec 19 17:04:05 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Danilo Krummrich X-Patchwork-Id: 13915382 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id A718318A6B2; Thu, 19 Dec 2024 17:04:55 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734627895; cv=none; b=k6onwBaRmzd1xNOMIgIEC7H16+02MdrfKl2UUjiChpdbW1inXg3c8sQ6MkdHdZmtbrpYY8KmujJqaKu4XivnmpPVL1+b5mJOAbKBc54q8h/18xFaEXIVOwvVZbfPNTBvOLM3XHlw75JxK0FEWqrMBZmYTZV07c86KvF7mfEWKHk= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1734627895; c=relaxed/simple; bh=W46QjF8inycgk2VyR/5aAaI9t59wmJm3DxD7pQsN9qA=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=flwLPfA8PGGDOMPtDKy4KywOZNZ/1CYjE3CW46H3FcW6FG8A6tzYeXnvoQPKgUtdPNeXSD6blXqw2L7sw1kxnr4eSOAmt2feH6VRvUjn4HOFSZq9s1EnEUi2j07JOTcyH/k4hJnhKOs0ugEqE1Ycj/YJe3YnId6sY5ngwqy8rn8= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=r4eA6bGd; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="r4eA6bGd" Received: by smtp.kernel.org (Postfix) with ESMTPSA id C7F14C4CED6; Thu, 19 Dec 2024 17:04:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1734627895; bh=W46QjF8inycgk2VyR/5aAaI9t59wmJm3DxD7pQsN9qA=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=r4eA6bGdHddFeaVJ2zw1MUv1/u2rA4lDlCdZ8s/6pUEVGN5BPKla/YhEfg3Ke7R/s b+i53Ev1Di1nchRCyKyo25c5iSa9NfiIMp/OrtjD6hKOyxVjBbFjIr+ADJxlFuX+iE lJ1uffGJfCDk50MOsCK6ujwtWZMjPLIUmTAYmQYqDNaPrTS+J1SwvvjZy4DS507aUS 7a+8WyEdLU56SUppcG1y07ATgXR9CH2+HHkbSm+y4kM7/tkozGW8P2zL8o6mC2LwXE bPzKr1H83qFTfFLF7vEyqRA3aWtlxw/zCW8sLrstQhTtfSI5mVpI7+ah6CuF8GzCrp D6avboaREv27w== From: Danilo Krummrich To: gregkh@linuxfoundation.org, rafael@kernel.org, bhelgaas@google.com, ojeda@kernel.org, alex.gaynor@gmail.com, boqun.feng@gmail.com, gary@garyguo.net, bjorn3_gh@protonmail.com, benno.lossin@proton.me, tmgross@umich.edu, a.hindborg@samsung.com, aliceryhl@google.com, airlied@gmail.com, fujita.tomonori@gmail.com, lina@asahilina.net, pstanner@redhat.com, ajanulgu@redhat.com, lyude@redhat.com, robh@kernel.org, daniel.almeida@collabora.com, saravanak@google.com, dirk.behme@de.bosch.com, j@jannau.net, fabien.parent@linaro.org, chrisi.schrefl@gmail.com, paulmck@kernel.org Cc: rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, devicetree@vger.kernel.org, rcu@vger.kernel.org, Danilo Krummrich , Wedson Almeida Filho Subject: [PATCH v7 03/16] rust: implement `IdArray`, `IdTable` and `RawDeviceId` Date: Thu, 19 Dec 2024 18:04:05 +0100 Message-ID: <20241219170425.12036-4-dakr@kernel.org> X-Mailer: git-send-email 2.47.1 In-Reply-To: <20241219170425.12036-1-dakr@kernel.org> References: <20241219170425.12036-1-dakr@kernel.org> Precedence: bulk X-Mailing-List: rcu@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Most subsystems use some kind of ID to match devices and drivers. Hence, we have to provide Rust drivers an abstraction to register an ID table for the driver to match. Generally, those IDs are subsystem specific and hence need to be implemented by the corresponding subsystem. However, the `IdArray`, `IdTable` and `RawDeviceId` types provide a generalized implementation that makes the life of subsystems easier to do so. Co-developed-by: Wedson Almeida Filho Signed-off-by: Wedson Almeida Filho Co-developed-by: Gary Guo Signed-off-by: Gary Guo Co-developed-by: Fabien Parent Signed-off-by: Fabien Parent Signed-off-by: Danilo Krummrich --- MAINTAINERS | 1 + rust/kernel/device_id.rs | 165 +++++++++++++++++++++++++++++++++++++++ rust/kernel/lib.rs | 6 ++ 3 files changed, 172 insertions(+) create mode 100644 rust/kernel/device_id.rs diff --git a/MAINTAINERS b/MAINTAINERS index 2ad58ed40079..3cfb68650347 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -7033,6 +7033,7 @@ F: include/linux/kobj* F: include/linux/property.h F: lib/kobj* F: rust/kernel/device.rs +F: rust/kernel/device_id.rs F: rust/kernel/driver.rs DRIVERS FOR OMAP ADAPTIVE VOLTAGE SCALING (AVS) diff --git a/rust/kernel/device_id.rs b/rust/kernel/device_id.rs new file mode 100644 index 000000000000..e5859217a579 --- /dev/null +++ b/rust/kernel/device_id.rs @@ -0,0 +1,165 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Generic implementation of device IDs. +//! +//! Each bus / subsystem that matches device and driver through a bus / subsystem specific ID is +//! expected to implement [`RawDeviceId`]. + +use core::mem::MaybeUninit; + +/// Marker trait to indicate a Rust device ID type represents a corresponding C device ID type. +/// +/// This is meant to be implemented by buses/subsystems so that they can use [`IdTable`] to +/// guarantee (at compile-time) zero-termination of device id tables provided by drivers. +/// +/// # Safety +/// +/// 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. +/// +/// 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. + const DRIVER_DATA_OFFSET: usize; + + /// The index stored at `DRIVER_DATA_OFFSET` of the implementor of the [`RawDeviceId`] trait. + fn index(&self) -> usize; +} + +/// A zero-terminated device id array. +#[repr(C)] +pub struct RawIdArray { + ids: [T::RawType; N], + sentinel: MaybeUninit, +} + +impl RawIdArray { + #[doc(hidden)] + pub const fn size(&self) -> usize { + core::mem::size_of::() + } +} + +/// A zero-terminated device id array, followed by context data. +#[repr(C)] +pub struct IdArray { + raw_ids: RawIdArray, + id_infos: [U; N], +} + +impl IdArray { + /// 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 { + let mut raw_ids = [const { MaybeUninit::::uninit() }; N]; + let mut infos = [const { MaybeUninit::uninit() }; N]; + + let mut i = 0usize; + while i < 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::() + .write(i); + } + + // SAFETY: this is effectively a move: `infos[i] = ids[i].1`. We make a copy here but + // later forget `ids`. + infos[i] = MaybeUninit::new(unsafe { core::ptr::read(&ids[i].1) }); + i += 1; + } + + core::mem::forget(ids); + + Self { + raw_ids: RawIdArray { + // SAFETY: this is effectively `array_assume_init`, which is unstable, so we use + // `transmute_copy` instead. We have initialized all elements of `raw_ids` so this + // `array_assume_init` is safe. + ids: unsafe { core::mem::transmute_copy(&raw_ids) }, + sentinel: MaybeUninit::zeroed(), + }, + // SAFETY: We have initialized all elements of `infos` so this `array_assume_init` is + // safe. + id_infos: unsafe { core::mem::transmute_copy(&infos) }, + } + } + + /// Reference to the contained [`RawIdArray`]. + pub const fn raw_ids(&self) -> &RawIdArray { + &self.raw_ids + } +} + +/// A device id table. +/// +/// This trait is only implemented by `IdArray`. +/// +/// The purpose of this trait is to allow `&'static dyn IdArray` to be in context when `N` in +/// `IdArray` doesn't matter. +pub trait IdTable { + /// Obtain the pointer to the ID table. + fn as_ptr(&self) -> *const T::RawType; + + /// Obtain the pointer to the bus specific device ID from an index. + fn id(&self, index: usize) -> &T::RawType; + + /// Obtain the pointer to the driver-specific information from an index. + fn info(&self, index: usize) -> &U; +} + +impl IdTable for IdArray { + fn as_ptr(&self) -> *const T::RawType { + // This cannot be `self.ids.as_ptr()`, as the return pointer must have correct provenance + // to access the sentinel. + (self as *const Self).cast() + } + + fn id(&self, index: usize) -> &T::RawType { + &self.raw_ids.ids[index] + } + + fn info(&self, index: usize) -> &U { + &self.id_infos[index] + } +} + +/// Create device table alias for modpost. +#[macro_export] +macro_rules! module_device_table { + ($table_type: literal, $module_table_name:ident, $table_name:ident) => { + #[rustfmt::skip] + #[export_name = + concat!("__mod_device_table__", $table_type, + "__", module_path!(), + "_", line!(), + "_", stringify!($table_name)) + ] + static $module_table_name: [core::mem::MaybeUninit; $table_name.raw_ids().size()] = + unsafe { core::mem::transmute_copy($table_name.raw_ids()) }; + }; +} diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 7818407f9aac..66149ac5c0c9 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -18,6 +18,11 @@ #![feature(inline_const)] #![feature(lint_reasons)] #![feature(unsize)] +// Stable in Rust 1.83 +#![feature(const_maybe_uninit_as_mut_ptr)] +#![feature(const_mut_refs)] +#![feature(const_ptr_write)] +#![feature(const_refs_to_cell)] // Ensure conditional compilation based on the kernel configuration works; // otherwise we may silently break things like initcall handling. @@ -35,6 +40,7 @@ mod build_assert; pub mod cred; pub mod device; +pub mod device_id; pub mod driver; pub mod error; #[cfg(CONFIG_RUST_FW_LOADER_ABSTRACTIONS)]