linux-kernel - Re: [PATCH v9 2/5] rust: add bindings for bitops.h

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Message-ID: <6835eaa4.c80a0220.2baf57.d14b@mx.google.com>
Date: Tue, 27 May 2025 09:38:58 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Burak Emir <bqe@...gle.com>
Cc: Yury Norov <yury.norov@...il.com>, Kees Cook <kees@...nel.org>,
	Rasmus Villemoes <linux@...musvillemoes.dk>,
	Viresh Kumar <viresh.kumar@...aro.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>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	"Gustavo A . R . Silva" <gustavoars@...nel.org>,
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH v9 2/5] rust: add bindings for bitops.h

On Mon, May 26, 2025 at 03:01:31PM +0000, Burak Emir wrote:
> Makes atomic set_bit and clear_bit inline functions as well as the
> non-atomic variants __set_bit and __clear_bit available to Rust.
> Adds a new MAINTAINERS section BITOPS API BINDINGS [RUST].
> 
> Suggested-by: Alice Ryhl <aliceryhl@...gle.com>
> Suggested-by: Yury Norov <yury.norov@...il.com>
> Signed-off-by: Burak Emir <bqe@...gle.com>
> Acked-by: Yury Norov [NVIDIA] <yury.norov@...il.com>
> ---
>  MAINTAINERS            |  5 +++++
>  rust/helpers/bitops.c  | 23 +++++++++++++++++++++++
>  rust/helpers/helpers.c |  1 +
>  3 files changed, 29 insertions(+)
>  create mode 100644 rust/helpers/bitops.c
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 86cae0ca5287..04d6727e944c 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -4141,6 +4141,11 @@ F:	include/linux/bitops.h
>  F:	lib/test_bitops.c
>  F:	tools/*/bitops*
>  
> +BITOPS API BINDINGS [RUST]
> +M:	Yury Norov <yury.norov@...il.com>
> +S:	Maintained
> +F:	rust/helpers/bitops.c
> +
>  BLINKM RGB LED DRIVER
>  M:	Jan-Simon Moeller <jansimon.moeller@....de>
>  S:	Maintained
> diff --git a/rust/helpers/bitops.c b/rust/helpers/bitops.c
> new file mode 100644
> index 000000000000..1fe9e3b23a39
> --- /dev/null
> +++ b/rust/helpers/bitops.c
> @@ -0,0 +1,23 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/bitops.h>
> +
> +void rust_helper___set_bit(unsigned int nr, unsigned long *addr)

Why "unsigned int" instead of "unsigned long"? The C API uses
"unsigned long" and in the Rust API, you uses "usize" for `nbits` and
`index`s, therefore using "unsigned int" only introduces unnecessary "as
u32" casting IMO, am I missing something here?

Regards,
Boqun

> +{
> +	__set_bit(nr, addr);
> +}
> +
> +void rust_helper___clear_bit(unsigned int nr, unsigned long *addr)
> +{
> +	__clear_bit(nr, addr);
> +}
> +
> +void rust_helper_set_bit(unsigned int nr, volatile unsigned long *addr)
> +{
> +	set_bit(nr, addr);
> +}
> +
> +void rust_helper_clear_bit(unsigned int nr, volatile unsigned long *addr)
> +{
> +	clear_bit(nr, addr);
> +}
> diff --git a/rust/helpers/helpers.c b/rust/helpers/helpers.c
> index 92721d165e35..4de8ac390241 100644
> --- a/rust/helpers/helpers.c
> +++ b/rust/helpers/helpers.c
> @@ -8,6 +8,7 @@
>   */
>  
>  #include "bitmap.c"
> +#include "bitops.c"
>  #include "blk.c"
>  #include "bug.c"
>  #include "build_assert.c"
> -- 
> 2.49.0.1151.ga128411c76-goog
>