linux-kernel - Re: [PATCH v2 4/5] rust: enable `clippy::as_ptr_cast

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Message-ID: <D8DGL6WY04GZ.207MFVQMKY35G@proton.me>
Date: Tue, 11 Mar 2025 13:08:19 +0000
From: Benno Lossin <benno.lossin@...ton.me>
To: Tamir Duberstein <tamird@...il.com>, Masahiro Yamada <masahiroy@...nel.org>, Nathan Chancellor <nathan@...nel.org>, Nicolas Schier <nicolas@...sle.eu>, Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, Andreas Hindborg <a.hindborg@...nel.org>, Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, Danilo Krummrich <dakr@...nel.org>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>, "Rafael J. Wysocki" <rafael@...nel.org>, Brendan Higgins <brendan.higgins@...ux.dev>, David Gow <davidgow@...gle.com>, Rae Moar <rmoar@...gle.com>, Bjorn Helgaas <bhelgaas@...gle.com>, Luis Chamberlain <mcgrof@...nel.org>, Russ Weight <russ.weight@...ux.dev>, Rob Herring <robh@...nel.org>, Saravana Kannan <saravanak@...gle.com>
Cc: linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org, linux-kselftest@...r.kernel.org, kunit-dev@...glegroups.com, linux-pci@...r.kernel.org, linux-block@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v2 4/5] rust: enable `clippy::as_ptr_cast_mut` lint

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@...il.com>

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

---
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(),
>              )
>          };
>