Re: [PATCH v2 4/5] rust: enable `clippy::as_ptr_cast_mut` lint

[Benno Lossin]

On Sun Mar 9, 2025 at 5:00 PM CET, Tamir Duberstein wrote:
> In Rust 1.66.0, Clippy introduced the `as_ptr_cast_mut` lint [1]:
>
>> Since `as_ptr` takes a `&self`, the pointer won’t have write
>> permissions unless interior mutability is used, making it unlikely
>> that having it as a mutable pointer is correct.
>
> There is only one affected callsite, and the change amounts to replacing
> `as _` with `.cast_mut().cast()`. This doesn't change the semantics, but
> is more descriptive of what's going on.
>
> Apply this change and enable the lint -- no functional change intended.
>
> Link: https://rust-lang.github.io/rust-clippy/master/index.html#as_ptr_cast_mut [1]
> Signed-off-by: Tamir Duberstein <tamird@xxxxxxxxx>

Reviewed-by: Benno Lossin <benno.lossin@xxxxxxxxx>

---
Cheers,
Benno

> ---
>  Makefile              | 1 +
>  rust/kernel/devres.rs | 2 +-
>  2 files changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/Makefile b/Makefile
> index c62bae2b107b..bb15b86182a3 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -477,6 +477,7 @@ export rust_common_flags := --edition=2021 \
>  			    -Wrust_2018_idioms \
>  			    -Wunreachable_pub \
>  			    -Wclippy::all \
> +			    -Wclippy::as_ptr_cast_mut \
>  			    -Wclippy::ignored_unit_patterns \
>  			    -Wclippy::mut_mut \
>  			    -Wclippy::needless_bitwise_bool \
> diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs
> index 3a9d998ec371..598001157293 100644
> --- a/rust/kernel/devres.rs
> +++ b/rust/kernel/devres.rs
> @@ -143,7 +143,7 @@ fn remove_action(this: &Arc<Self>) {
>              bindings::devm_remove_action_nowarn(
>                  this.dev.as_raw(),
>                  Some(this.callback),
> -                this.as_ptr() as _,
> +                this.as_ptr().cast_mut().cast(),
>              )
>          };
>