Re: [PATCH v11 1/4] rust: io: add resource abstraction

[Danilo Krummrich <dakr@kernel.org>]

On Wed, Jul 02, 2025 at 03:11:04PM -0300, Daniel Almeida wrote:
> Hi Danilo
> 
> > On 2 Jul 2025, at 07:21, Danilo Krummrich <dakr@kernel.org> wrote:
> > 
> >> +#[cfg(CONFIG_HAS_IOPORT)]
> >> +/// Returns a reference to the global `ioport_resource` variable.
> >> +pub fn ioport_resource() -> &'static Resource {
> >> +    // SAFETY: `bindings::ioport_resoure` has global lifetime and is of type Resource.
> >> +    unsafe { Resource::as_ref(&raw mut bindings::ioport_resource) }
> >> +}
> >> +
> >> +#[cfg(CONFIG_HAS_IOMEM)]
> >> +/// Returns a reference to the global `iomem_resource` variable.
> >> +pub fn iomem_resource() -> &'static Resource {
> >> +    // SAFETY: `bindings::iomem_resoure` has global lifetime and is of type Resource.
> >> +    unsafe { Resource::as_ref(&raw mut bindings::iomem_resource) }
> >> +}
> > 
> > This caught my attention, and I have a few questions:
> > 
> >  1) What do you need them for? I don't see any methods that would usually
> >     consume those.
> > 
> >  2) Why are they behind CONFIG_HAS_IOPORT and CONFIG_HAS_IOMEM, even though the
> >     C instances are not?
> > 
> >  3) What happens if we pass them to IoMem::new()? Is this really safe, or do we
> >     need them to be a special Resource type?
> > 
> 
> Good catch, actually.
> 
> I worked on this patch with Fiona and IIRC, she needed access to these two for
> her LED abstractions. This patch has seen a few iterations already and this may
> or may not be obsolete by now. I must say I've never used these before so I
> don't really know how they work nor do I need this at all.

They serve as parent / root resource instances, e.g. if you want to create new
resource regions yourself.

> Fiona, do you still need these two accessors?

I'd say let's drop them for now, we can easily add them later on in the context
of an actual user.