Re: [PATCH net-next v2 1/6] rust: sizes: add commonly used constants

[Alice Ryhl <aliceryhl@google.com>]

On Wed, Jul 31, 2024 at 2:17 PM Andrew Lunn <andrew@lunn.ch> wrote:
>
> On Wed, Jul 31, 2024 at 01:21:31PM +0900, FUJITA Tomonori wrote:
> > Add rust equivalent to include/linux/sizes.h, makes code more
> > readable. This adds only SZ_*K, which mostly used.
> >
> > Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
> > ---
> >  rust/kernel/lib.rs   |  1 +
> >  rust/kernel/sizes.rs | 26 ++++++++++++++++++++++++++
> >  2 files changed, 27 insertions(+)
> >  create mode 100644 rust/kernel/sizes.rs
> >
> > diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> > index e6b7d3a80bbc..ba2ba996678d 100644
> > --- a/rust/kernel/lib.rs
> > +++ b/rust/kernel/lib.rs
> > @@ -42,6 +42,7 @@
> >  pub mod net;
> >  pub mod prelude;
> >  pub mod print;
> > +pub mod sizes;
> >  mod static_assert;
> >  #[doc(hidden)]
> >  pub mod std_vendor;
> > diff --git a/rust/kernel/sizes.rs b/rust/kernel/sizes.rs
> > new file mode 100644
> > index 000000000000..834c343e4170
> > --- /dev/null
> > +++ b/rust/kernel/sizes.rs
> > @@ -0,0 +1,26 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +//! Commonly used sizes.
> > +//!
> > +//! C headers: [`include/linux/sizes.h`](srctree/include/linux/sizes.h).
> > +
> > +/// 0x00000400
> > +pub const SZ_1K: usize = bindings::SZ_1K as usize;
>
> 1K is 1K, independent of it being C 1K or Rust 1K. In this case, does
> it makes sense to actually use the C header? I don't know? But the
> Rust people seems to think this is O.K.

Shrug. I don't think it really matters.

If using the C header required adding constants in
rust/bindings/bindings_helper.h to actually make the constants usable
from Rust, then I would say we should just set the constants from the
Rust side. But in this case using the C header just works so I don't
think it's an issue.

Alice