Re: [PATCH] rust: bindings: derive Zeroable for bindgen's opaque array wrappers

[Alice Ryhl]

On Sat, Oct 31, 2026 at 5:29 PM Sasha Levin <sashal@xxxxxxxxxx> wrote:
>
> On Sat, Oct 31, 2026 at 05:17:46PM +0100, Alice Ryhl wrote:
> >Is it possible to instead fix this by adding the impl of Zeroable in
> >rust/bindings/lib.rs, similar to this piece of code that we already
> >have:
> >
> >unsafe impl<Storage> Zeroable for __BindgenBitfieldUnit<Storage> where
> >Storage: Zeroable {}
>
> I looked at doing it that way, but the wrapper types don't always exist,
> so a fixed impl in lib.rs won't build everywhere:
>
>  - bindgen 0.71 and 0.72 (we still support 0.71.1) don't generate them
>    at all, the blob is a plain array there.
>
>  - 0.73 only emits the alignments a config actually needs. On x86_64,
>    allmodconfig gets __BindgenOpaqueArray, __BindgenOpaqueArray8,
>    __BindgenOpaqueArray64 and __BindgenOpaqueArray4096, but defconfig
>    with Rust enabled has no __BindgenOpaqueArray4096, so an impl for it
>    would break the build there.
>
> __BindgenBitfieldUnit works because it's always generated. We could do it
> in lib.rs with a Kconfig symbol for the bindgen version plus some way to
> know which alignments a config ends up with, but tagging the wrappers
> right after bindgen runs seemed simpler.

Fair enough!

Reviewed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>