Re: [PATCH] drm/tyr: suppress unread field warnings

[Alice Ryhl <aliceryhl@google.com>]

On Fri, Jan 23, 2026 at 04:01:42PM +0100, Miguel Ojeda wrote:
> On Thu, Jan 22, 2026 at 8:46 PM Danilo Krummrich <dakr@kernel.org> wrote:
> >
> > If I run 1.85.0, I *instead* see the following ones from clippy:
> >
> >   CLIPPY [M] drivers/gpu/drm/tyr/tyr.o
> > warning: operator precedence can trip the unwary
> >   --> drivers/gpu/drm/tyr/gpu.rs:51:13
> >    |
> > 51 |             shader_present | u64::from(regs::GPU_SHADER_PRESENT_HI.read(dev, iomem)?) << 32;
> >    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: consider parenthesizing your expression: `shader_present | (u64::from(regs::GPU_SHADER_PRESENT_HI.read(dev, iomem)?) << 32)`
> >    |
> >    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#precedence
> >    = note: `-W clippy::precedence` implied by `-W clippy::all`
> >    = help: to override `-W clippy::all` add `#[allow(clippy::precedence)]`
> 
> I took a look at this --  Rust 1.85.0 extended the `precedence` lint
> to catch these, and then because it was too much, they split part of
> it into a new one called `precedence_bits` which is not enabled by
> default, which landed in Rust 1.86.0 (and is not in Rust 1.85.1,
> sadly).
> 
>     https://github.com/rust-lang/rust-clippy/pull/13743
>     https://github.com/rust-lang/rust-clippy/issues/14097
>     https://github.com/rust-lang/rust-clippy/pull/14115
> 
> I see others in the kernel have written similar expressions with
> parenthesis, e.g. for Rust in `ioctl.rs`, and I see a ton of those in
> C files too.
> 
> Personally, I don't mind seeing the parenthesis, but I know others may
> feel like it is obvious.
> 
> Now, seeing quite a bunch of parenthesis for this in C files, from
> kernel devs and crypto stuff and all over drivers and so on and so
> forth, means others definitely do not find it obvious or prefer to be
> explicit for extra clarity.
> 
> So we can just clean this one up and later enable `precedence_bits`
> for newer versions. Or if we decided it is too much, then I guess I
> could allow `precedence` on Rust 1.85.0 only.
> 
> Cc'ing others in case they want to give their opinion.

Having a lint that happens on just one random version is inconvenient,
so I think we should take at least one of these two actions:

1. Disable clippy::precedence on 1.85.0 only.
2. Enable the clippy::precedence_bits lint.

But I am ok with enabling clippy::precedence_bits.

Alice