[PATCH 1/3] rust: add `num` module with `PowerOfTwo` type

[Alexandre Courbot]

On Mon Aug 4, 2025 at 12:15 AM JST, Miguel Ojeda wrote:
> On Sun, Aug 3, 2025 at 3:13 PM Alexandre Courbot <acourbot at nvidia.com> wrote:
>>
>> We got some interesting feedback on the ACP already. I have been pointed
>> to `checked_ilog2` as an equivalent of `last_set_bit`, and it *does*
>> indeed work well as a replacement - with the caveat that the name is
>> not very natural to me (or anyone familiar with the C interface). Is
>> this something we can live with? If we decide to go with the existing
>> standard library method, how can we make sure that folks looking for an
>> equivalent of `fls` find `checked_ilog2`?
>
> One option is using the `doc(alias = ...)` attribute, which makes it
> appear in the search in the rendered docs, and would show easily in
> greps too.
>
> Another option is simply wrapping it in an `inline(always)`, I guess,
> but I think we can just use the upstream ones, unless we want slightly
> different semantics.

That would be useful - let's see what the Rust lib folks say, as you
brought up that question on the ACP as well.

In any case, since we have reasonable alternatives for both `fls`
(`checked_ilog2`) and `ffs` (`NonZero::trailing_zeros`), I guess this
means we want to use these directly in the kernel and can drop patch
2 of this series?