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Message-ID: <aKVFVO3wbzClcLwg@archiso>
Date: Wed, 20 Aug 2025 03:48:10 +0000
From: Elle Rhumsaa <elle@...thered-steel.dev>
To: John Hubbard <jhubbard@...dia.com>
Cc: Danilo Krummrich <dakr@...nel.org>,
Alexandre Courbot <acourbot@...dia.com>,
Joel Fernandes <joelagnelf@...dia.com>,
Timur Tabi <ttabi@...dia.com>, Alistair Popple <apopple@...dia.com>,
David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
Bjorn Helgaas <bhelgaas@...gle.com>,
Krzysztof Wilczyński <kwilczynski@...nel.org>,
Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>,
Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
Benno Lossin <lossin@...nel.org>,
Andreas Hindborg <a.hindborg@...nel.org>,
Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
nouveau@...ts.freedesktop.org, linux-pci@...r.kernel.org,
rust-for-linux@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/3] rust: pci: provide access to PCI Class, subclass,
implementation values
On Sun, Aug 17, 2025 at 06:33:03PM -0700, John Hubbard wrote:
> Allow callers to write Class::STORAGE_SCSI instead of
> bindings::PCI_CLASS_STORAGE_SCSI, for example.
>
> New APIs:
> Class::STORAGE_SCSI, Class::NETWORK_ETHERNET, etc.
> Class::from_u32(), as_u32()
> Class::MASK_FULL, MASK_CLASS_SUBCLASS
> DeviceId::from_class_and_vendor()
> Device::class_code_raw(), class_enum()
>
> Cc: Danilo Krummrich <dakr@...nel.org>
> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> ---
> rust/kernel/pci.rs | 202 +++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 202 insertions(+)
>
> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
> index 887ee611b553..9caa1d342d52 100644
> --- a/rust/kernel/pci.rs
> +++ b/rust/kernel/pci.rs
> @@ -23,6 +23,179 @@
> };
> use kernel::prelude::*;
>
> +macro_rules! define_all_pci_classes {
> + (
> + $($variant:ident = $binding:expr,)+
> + ) => {
> + /// Converts a PCI class constant to 24-bit format.
> + ///
> + /// Many device drivers use only the upper 16 bits (base class and subclass), but some
> + /// use the full 24 bits. In order to support both cases, store the class code as a 24-bit
> + /// value, where 16-bit values are shifted up 8 bits.
> + const fn to_24bit_class(val: u32) -> u32 {
> + if val > 0xFFFF { val } else { val << 8 }
> + }
> +
> + /// PCI device class codes.
> + ///
> + /// Each entry contains the full 24-bit PCI class code (base class in bits 23-16, subclass
> + /// in bits 15-8, programming interface in bits 7-0).
> + ///
> + #[derive(Debug, Clone, Copy, PartialEq, Eq)]
> + #[repr(transparent)]
> + pub struct Class(u32);
> +
> + impl Class {
> + $(
> + #[allow(missing_docs)]
> + pub const $variant: Self = Self(to_24bit_class($binding));
> + )+
> +
> + /// Match the full class code.
> + pub const MASK_FULL: u32 = 0xffffff;
> +
> + /// Match the upper 16 bits of the class code (base class and subclass only).
> + pub const MASK_CLASS_SUBCLASS: u32 = 0xffff00;
> +
> + /// Create a `Class` from the raw class code value, or `None` if the value doesn't
> + /// match any known class.
> + pub fn from_u32(value: u32) -> Option<Self> {
> + match value {
> + $(x if x == Self::$variant.0 => Some(Self::$variant),)+
> + _ => None,
> + }
> + }
> +
> + /// Get the raw 24-bit class code value.
> + pub const fn as_u32(self) -> u32 {
> + self.0
> + }
> + }
> + };
> +}
> +
> +define_all_pci_classes! {
> + NOT_DEFINED = bindings::PCI_CLASS_NOT_DEFINED, // 0x000000
> +
> + ...
> +
> + OTHERS = bindings::PCI_CLASS_OTHERS, // 0xff0000
> +}
> +
> /// An adapter for the registration of PCI drivers.
> pub struct Adapter<T: Driver>(T);
>
> @@ -157,6 +330,23 @@ pub const fn from_class(class: u32, class_mask: u32) -> Self {
> override_only: 0,
> })
> }
> +
> + /// Create a new `pci::DeviceId` from a class number, mask, and specific vendor.
> + ///
> + /// This is more targeted than [`DeviceId::from_class`]: in addition to matching by Vendor, it
> + /// also matches the PCI Class (up to the entire 24 bits, depending on the mask).
> + pub const fn from_class_and_vendor(class: Class, class_mask: u32, vendor: u32) -> Self {
> + Self(bindings::pci_device_id {
> + vendor,
> + device: DeviceId::PCI_ANY_ID,
> + subvendor: DeviceId::PCI_ANY_ID,
> + subdevice: DeviceId::PCI_ANY_ID,
> + class: class.as_u32(),
> + class_mask,
> + driver_data: 0,
> + override_only: 0,
> + })
> + }
> }
>
> // SAFETY: `DeviceId` is a `#[repr(transparent)]` wrapper of `pci_device_id` and does not add
> @@ -410,6 +600,18 @@ pub fn resource_len(&self, bar: u32) -> Result<bindings::resource_size_t> {
> // - by its type invariant `self.as_raw` is always a valid pointer to a `struct pci_dev`.
> Ok(unsafe { bindings::pci_resource_len(self.as_raw(), bar.try_into()?) })
> }
> +
> + /// Returns the full 24-bit PCI class code as stored in hardware.
> + /// This includes base class, subclass, and programming interface.
> + pub fn class_code_raw(&self) -> u32 {
> + // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
> + unsafe { (*self.as_raw()).class }
> + }
> +
> + /// Returns the PCI class as a `Class` struct, or `None` if the class code is invalid.
> + pub fn class_enum(&self) -> Option<Class> {
> + Class::from_u32(self.class_code_raw())
> + }
> }
>
> impl Device<device::Bound> {
> --
> 2.50.1
All of the functions could probably be `#[inline]`ed, though I'm not
sure how much it affects the `const` functions, since they're already
evaluated at compile-time.
Reviewed-by: Elle Rhumsaa <elle@...thered-steel.dev>
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