[v9] rust: adds Bitmap API, ID pool and bindings

[PATCH v9 2/5] rust: add bindings for bitops.h

Posted by Burak Emir 6 months, 3 weeks ago

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@google.com>
Suggested-by: Yury Norov <yury.norov@gmail.com>
Signed-off-by: Burak Emir <bqe@google.com>
Acked-by: Yury Norov [NVIDIA] <yury.norov@gmail.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@gmail.com>
+S:	Maintained
+F:	rust/helpers/bitops.c
+
 BLINKM RGB LED DRIVER
 M:	Jan-Simon Moeller <jansimon.moeller@gmx.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)
+{
+	__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

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

Posted by Boqun Feng 6 months, 3 weeks ago

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@google.com>
> Suggested-by: Yury Norov <yury.norov@gmail.com>
> Signed-off-by: Burak Emir <bqe@google.com>
> Acked-by: Yury Norov [NVIDIA] <yury.norov@gmail.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@gmail.com>
> +S:	Maintained
> +F:	rust/helpers/bitops.c
> +
>  BLINKM RGB LED DRIVER
>  M:	Jan-Simon Moeller <jansimon.moeller@gmx.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
>

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

Posted by Burak Emir 6 months, 2 weeks ago

On Tue, May 27, 2025 at 6:39 PM Boqun Feng <boqun.feng@gmail.com> wrote:
>
> On Mon, May 26, 2025 at 03:01:31PM +0000, Burak Emir wrote:
> > --- /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?

This is certainly a bit confusing to me.

As Jann points out here [1] the expand to asm macros arch___set_bit,
where `nr` is indeed unsigned long.

There is also the constraint that a bitmap's length must be shorter
than INT32_MAX bits, but that does not matter.

Being consistent with the C API, including parameter names, is what we
should do, so fixing this.
I found the underlying C API is just hard to find for these macros.
Thanks for catching.

cheers
- Burak

[1] https://lore.kernel.org/rust-for-linux/CAG48ez1NM7B8Vk7GOwhsitCipmfHi9eK6JNb3ve8aR4m8Cj0gA@mail.gmail.com/