linux-kernel - Re: [PATCH v7 2/6] rust: pci: provide access to PCI Vendor values

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Message-Id: <DCE3ENGCR4T7.25B37IKXHCC8O@nvidia.com>
Date: Thu, 28 Aug 2025 22:25:02 +0900
From: "Alexandre Courbot" <acourbot@...dia.com>
To: "John Hubbard" <jhubbard@...dia.com>, "Danilo Krummrich"
 <dakr@...nel.org>
Cc: "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>, "Elle Rhumsaa" <elle@...thered-steel.dev>
Subject: Re: [PATCH v7 2/6] rust: pci: provide access to PCI Vendor values

On Wed Aug 27, 2025 at 8:12 AM JST, John Hubbard wrote:
> This allows callers to write Vendor::SOME_COMPANY instead of
> bindings::PCI_VENDOR_ID_SOME_COMPANY.
>
> New APIs:
>     Vendor::SOME_COMPANY
>     Vendor::from_raw() -- Only accessible from the pci (parent) module.
>     Vendor::as_raw()
>     Vendor: fmt::Display for Vendor
>
> Cc: Danilo Krummrich <dakr@...nel.org>
> Cc: Alexandre Courbot <acourbot@...dia.com>
> Cc: Elle Rhumsaa <elle@...thered-steel.dev>
> Signed-off-by: John Hubbard <jhubbard@...dia.com>
> ---
>  rust/kernel/pci.rs    |   2 +-
>  rust/kernel/pci/id.rs | 349 +++++++++++++++++++++++++++++++++++++++++-
>  2 files changed, 349 insertions(+), 2 deletions(-)
>
> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
> index 212c4a6834fb..f15cfd0e76d9 100644
> --- a/rust/kernel/pci.rs
> +++ b/rust/kernel/pci.rs
> @@ -25,7 +25,7 @@
>  
>  mod id;
>  
> -pub use self::id::{Class, ClassMask};
> +pub use self::id::{Class, ClassMask, Vendor};
>  
>  /// An adapter for the registration of PCI drivers.
>  pub struct Adapter<T: Driver>(T);
> diff --git a/rust/kernel/pci/id.rs b/rust/kernel/pci/id.rs
> index 55d9cdcc6658..4b0ad8d4edc6 100644
> --- a/rust/kernel/pci/id.rs
> +++ b/rust/kernel/pci/id.rs
> @@ -2,7 +2,7 @@
>  
>  //! PCI device identifiers and related types.
>  //!
> -//! This module contains PCI class codes and supporting types.
> +//! This module contains PCI class codes, Vendor IDs, and supporting types.
>  
>  use crate::{bindings, error::code::EINVAL, error::Error, prelude::*};
>  use core::fmt;
> @@ -109,6 +109,69 @@ fn try_from(value: u32) -> Result<Self, Self::Error> {
>      }
>  }
>  
> +/// PCI vendor IDs.
> +///
> +/// Each entry contains the 16-bit PCI vendor ID as assigned by the PCI SIG.
> +///
> +/// # Examples
> +///
> +/// ```
> +/// # use kernel::{device::Core, pci::{self, Vendor}, prelude::*};
> +/// fn log_device_info(pdev: &pci::Device<Core>) -> Result<()> {
> +///     // Compare raw vendor ID with known vendor constant
> +///     let vendor_id = pdev.vendor_id();
> +///     if vendor_id == Vendor::NVIDIA.as_raw() {
> +///         dev_info!(
> +///             pdev.as_ref(),
> +///             "Found NVIDIA device: 0x{:x}\n",
> +///             pdev.device_id()
> +///         );
> +///     }
> +///     Ok(())
> +/// }
> +/// ```
> +#[derive(Debug, Clone, Copy, PartialEq, Eq)]
> +#[repr(transparent)]
> +pub struct Vendor(u16);
> +
> +macro_rules! define_all_pci_vendors {
> +    (
> +        $($variant:ident = $binding:expr,)+
> +    ) => {
> +
> +        impl Vendor {

Why the blank line here? (same for the `define_all_pci_classes` in the
previous patch).

> +            $(
> +                #[allow(missing_docs)]
> +                pub const $variant: Self = Self($binding as u16);
> +            )+
> +        }
> +    };
> +}
> +
> +/// Once constructed, a `Vendor` contains a valid PCI Vendor ID.
> +impl Vendor {
> +    /// Create a Vendor from a raw 16-bit vendor ID.
> +    /// Only accessible from the parent pci module.
> +    #[expect(dead_code)]
> +    #[inline]
> +    pub(super) fn from_raw(vendor_id: u16) -> Self {
> +        Self(vendor_id)
> +    }
> +
> +    /// Get the raw 16-bit vendor ID value.
> +    #[inline]
> +    pub const fn as_raw(self) -> u16 {
> +        self.0
> +    }
> +}
> +
> +impl fmt::Display for Vendor {
> +    #[inline]
> +    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
> +        write!(f, "0x{:04x}", self.0)
> +    }
> +}

Possibly an exercice for a future patch, but do we want to display the
vendor name if it is defined, rather than its hex code (which is more
the job of `Debug`)? We could leverage the macro above to do that. The
same should be doable for the PCI classes.

I suspect strings for all the names already exist on the C side, in
which case we would want to reuse them instead of defining new ones.

Note that I don't think this needs to be done for this series - it's
just a thought as I was looking at this `Display` implementation that
looks more like a `Debug` one.