Re: [PATCH v4 1/3] rust: pci: provide access to PCI Class and Class-related items

["Danilo Krummrich" <dakr@kernel.org>]

On Wed Aug 20, 2025 at 5:08 AM CEST, 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::as_raw()
>     Class: TryFrom<u32> for Class
>     ClassMask: Full, ClassSubclass
>     DeviceId::from_class_and_vendor()
>     Device::pci_class()
>
> Cc: Danilo Krummrich <dakr@kernel.org>
> Cc: Alexandre Courbot <acourbot@nvidia.com>
> Signed-off-by: John Hubbard <jhubbard@nvidia.com>
> +    /// Returns the PCI class as a `Class` struct.
> +    /// Returns an error if the class code is not recognized.
> +    pub fn pci_class(&self) -> Result<Class> {
> +        // SAFETY: `self.as_raw` is a valid pointer to a `struct pci_dev`.
> +        Class::new(unsafe { (*self.as_raw()).class })
> +    }

I think all this turned out very nice!

One thing to reconsider would be whether we really want this to be fallible.

It's probably better to define a pci::Class::UNKNOWN and implement

	impl From<u32> for Class {
	    fn from(value: u32) -> Self {
	        match value {
	            $(x if x == Self::$variant.0 => Self::$variant,)+
	            _ => Self::UNKNOWN,
	        }
	    }
	}

instead.