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

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Message-Id: <DCE5LAQ8XWRQ.30YBZAIE63ECO@kernel.org>
Date: Thu, 28 Aug 2025 17:07:45 +0200
From: "Danilo Krummrich" <dakr@...nel.org>
To: "Alexandre Courbot" <acourbot@...dia.com>
Cc: "John Hubbard" <jhubbard@...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>,
 "Elle Rhumsaa" <elle@...thered-steel.dev>
Subject: Re: [PATCH v7 2/6] rust: pci: provide access to PCI Vendor values

On Thu Aug 28, 2025 at 3:25 PM CEST, Alexandre Courbot wrote:
> 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.

Yeah, this can be addressed subsequently; it might make sense to align Display
and Debug though. Currently, Vendor simply derives Debug, resulting in the
decimal value to be printed.