Re: [PATCH] rust: io: mem: Fix exclusive MMIO region requests

[Kwanghoon Son <asdfkwang@gmail.com>]

On Wed, Oct 28, 2026 at 02:12:54AM +0000, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
> - [Low] rust: io: dead_code warning in Resource::iomem() when CONFIG_HAS_IOMEM=n
> - [Low] rust: io: missing #[inline] annotation on Resource::iomem()
> --
> 
> commit 87df13a505aabe5d12ec487bcf72bfc859780ac8
> Author: Kwanghoon Son <asdfkwang@gmail.com>
> 
> rust: io: mem: Fix exclusive MMIO region requests
> 
> This commit updates ExclusiveIoMem::ioremap() to request the MMIO region
> from the global iomem_resource root via a new Resource::iomem() helper
> rather than from the device's own resource.
> 
> > diff --git a/rust/kernel/io/resource.rs b/rust/kernel/io/resource.rs
> > index 758ce62b3cce3..c99a2530186fc 100644
> > --- a/rust/kernel/io/resource.rs
> > +++ b/rust/kernel/io/resource.rs
> > @@ -79,6 +79,12 @@ unsafe impl Sync for Region {}
> >  pub struct Resource(Opaque<bindings::resource>);
> >  
> >  impl Resource {
> > +    /// Returns the global I/O memory resource root.
> > +    pub(crate) fn iomem() -> &'static Self {
> > +        // SAFETY: iomem_resource is permanent; C serializes resource-tree updates.
> > +        unsafe { Self::from_raw(&raw mut bindings::iomem_resource) }
> > +    }
> 
> [Severity: Low]
> Will Resource::iomem() in rust/kernel/io/resource.rs trigger a dead_code
> warning (or a build failure with CONFIG_WERROR=y) when CONFIG_RUST=y and
> CONFIG_HAS_IOMEM=n (for example, on ARCH=um or s390 without CONFIG_PCI)?
> 
> In rust/kernel/io.rs, the mem module is gated on CONFIG_HAS_IOMEM while the
> resource module is compiled unconditionally:
> 
>     #[cfg(CONFIG_HAS_IOMEM)]
>     pub mod mem;
>     pub mod poll;
>     pub mod register;
>     pub mod resource;
> 
> Since the only caller of pub(crate) fn iomem() is ExclusiveIoMem::ioremap() in
> rust/kernel/io/mem.rs, should Resource::iomem() also be annotated with
> #[cfg(CONFIG_HAS_IOMEM)] (or made pub)?

I reproduced the dead_code warning.
I'll add #[cfg(CONFIG_HAS_IOMEM)] in v2, matching the condition on its only caller.

> 
> [Severity: Low]
> This isn't a bug, but should Resource::iomem() in rust/kernel/io/resource.rs
> also have an #[inline] attribute, matching the other small helper functions in
> the kernel crate abstractions?

I'd prefer to follow those and leave it without the attribute, unless
there is a specific reason to add it here.

I'll wait more reviews on this and send send v2!

Best regards,
Kwang.

> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/20261027-b4-rust-iomem-origin-master-fix-v1-1-16215ae197af@gmail.com?part=1