Re: [PATCH v4] rust: pci: reject IRQ vector indices that do not fit in u32

[Alexandre Courbot]

On Tue Sep 1, 2026 at 8:08 PM JST, Danilo Krummrich wrote:
> On Tue Sep 1, 2026 at 12:58 PM CEST, Alexandre Courbot wrote:
>> That makes me wonder, shouldn't we make `index` take a `u32` directly?
>> If that's what the C API expects, it does make sense to align to it
>> instead of forcing users to make a potential unneeded conversion if they
>> already have a u32.
>
> I intentionally did not do this, as the common type for an index is usize. Thus,
> I do not expect anyone to already have a u32, but to already have a usize, e.g.
> from some iterator.
>
> The fact that the C API did pick unsigned int as index type is an implementation
> detail the abstraction should bother with.

Thanks for the clarification (and Miguel for elaborating - I wasn't
completely aware of it!). In that case this patch looks correct to me.

Note that there is another `as` right after, in the same method:

  if irq < 0 {
      return Err(Error::from_errno(irq));
  }

  // SAFETY: `irq` is a valid IRQ number for `self.dev`, resolved from this registration.
  Ok(unsafe { IrqVector::new(IrqRequest::new(self.dev.as_ref(), irq as u32), self) })


We could get rid of it by replacing the `if irq < 0` test with:

  let irq = u32::try_from(irq).map_err(|_| Error::from_errno(irq))?;

Sophon, if you feel like doing it I think this could improve the patch
further.