Re: [PATCH 1/2] rust: pci: add domain_nr() accessor

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential
issue to consider:
- [Medium] rust: pci: signature mismatch in rust_helper_pci_domain_nr()
  on ppc and s390
--

commit 40ebd2410b826b9813de5dae1bbe6075723a08bc
Author: John Hubbard <jhubbard@nvidia.com>

rust: pci: add domain_nr() accessor

This commit adds a domain_nr() accessor to pci::Device and a corresponding
rust_helper_pci_domain_nr() C helper to retrieve the PCI domain number.

> diff --git a/rust/helpers/pci.c b/rust/helpers/pci.c
> index a8540f90b13ce..49f2c089d2369 100644
> --- a/rust/helpers/pci.c
> +++ b/rust/helpers/pci.c
> @@ -7,6 +7,11 @@ __rust_helper u16 rust_helper_pci_dev_id(struct pci_dev *dev)
>  	return PCI_DEVID(dev->bus->number, dev->devfn);
>  }
>  
> +__rust_helper int rust_helper_pci_domain_nr(struct pci_dev *dev)
> +{
> +	return pci_domain_nr(dev->bus);
> +}
> +
>  __rust_helper resource_size_t
>  rust_helper_pci_resource_start(struct pci_dev *pdev, int bar)
>  {
> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
> index 769d01d234296..57718e48208d5 100644
> --- a/rust/kernel/pci.rs
> +++ b/rust/kernel/pci.rs
> @@ -408,6 +408,20 @@ pub fn dev_id(&self) -> u16 {
>          unsafe { bindings::pci_dev_id(self.as_raw()) }
>      }
>  
> +    /// Returns the PCI domain number of the bus that this device is on.
> +    #[inline]
> +    pub fn domain_nr(&self) -> u32 {
> +        // SAFETY: By its type invariant `self.as_raw` is always a valid pointer to a
> +        // `struct pci_dev`.
> +        let domain_nr = unsafe { bindings::pci_domain_nr(self.as_raw()) };

[Severity: Medium]
Does bindings::pci_domain_nr(self.as_raw()) fail to compile on PowerPC and
s390 due to a pointer type mismatch?

In rust/bindings/lib.rs, bindings_generated.rs is included after
pub use super::bindings_helper::*, so any non-inline C function emitted by
bindgen shadows a rust_helper_* wrapper of the same stripped name.  On PowerPC
(arch/powerpc/include/asm/pci.h) and s390 (arch/s390/include/asm/pci.h),
pci_domain_nr() is declared as a non-inline extern function taking
struct pci_bus * rather than a static inline function:

arch/powerpc/include/asm/pci.h:
extern int pci_domain_nr(struct pci_bus *bus);

On those architectures, bindings::pci_domain_nr resolves to the C declaration
expecting *mut bindings::pci_bus instead of the helper's
*mut bindings::pci_dev, breaking the build when CONFIG_RUST and CONFIG_PCI are
enabled.  Either rust_helper_pci_domain_nr() should take struct pci_bus *bus to
match the C signature (with domain_nr() passing (*self.as_raw()).bus), or the
helper should use a distinct name that does not collide with C pci_domain_nr().

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261110033655.148487-1-jhubbard@nvidia.com?part=1