linux-kernel - Re: [PATCH v9 3/6] rust: enable `clippy::as_ptr_cast

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Message-ID: <680136c9.d40a0220.3a40bc.0bd0@mx.google.com>
Date: Thu, 17 Apr 2025 10:13:42 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Tamir Duberstein <tamird@...il.com>
Cc: Masahiro Yamada <masahiroy@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
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Subject: Re: [PATCH v9 3/6] rust: enable `clippy::as_ptr_cast_mut` lint

On Wed, Apr 16, 2025 at 01:36:07PM -0400, 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]
> Reviewed-by: Benno Lossin <benno.lossin@...ton.me>
> Signed-off-by: Tamir Duberstein <tamird@...il.com>

Reviewed-by: Boqun Feng <boqun.feng@...il.com>

Regards,
Boqun

> ---
>  Makefile              | 1 +
>  rust/kernel/devres.rs | 2 +-
>  2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/Makefile b/Makefile
> index 7b85b2a8d371..04a5246171f9 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -474,6 +474,7 @@ 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 9e649d70716a..f7e8f5f53622 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(),
>              )
>          };
>  
> 
> -- 
> 2.49.0
>