Re: [PATCH v3 1/3] rust: num: add cv! macro to create values from constant expressions

[Gary Guo]

On Wed Sep 2, 2026 at 10:16 AM BST, Eliot Courtney wrote:
> Currently, using NonZero/Bounded constants is quite verbose. It's
> unfortunate because it disincentivizes using it in interface boundaries.
> Introduce a macro to make it nicer to use. The macro `cv!` (for constant
> value) takes a const integer expression and widens it to i128 (at build
> time only) before passing it as a const generic value to a new trait
> `FromConst`. The value is then converted and appears in the
> associated constant `FromConst::VALUE`. The trait is implemented by
> NonZero, Bounded, and Alignment and lets values of each be constructed
> from constants without a verbose turbofish syntax.
> For example, `const { NonZero::new(1).unwrap() }` can be written as
> `cv!(1)`.
>
> Suggested-by: Gary Guo <gary@xxxxxxxxxxx>
> Signed-off-by: Eliot Courtney <ecourtney@xxxxxxxxxx>

Reviewed-by: Gary Guo <gary@xxxxxxxxxxx>

> ---
>  rust/kernel/num.rs         | 138 +++++++++++++++++++++++++++++++++++++++++++++
>  rust/kernel/num/bounded.rs |  19 +++++++
>  rust/kernel/ptr.rs         |  14 +++++
>  3 files changed, 171 insertions(+)
>
> diff --git a/rust/kernel/num.rs b/rust/kernel/num.rs
> index dbe848e30efe..9435459376a4 100644
> --- a/rust/kernel/num.rs
> +++ b/rust/kernel/num.rs
> @@ -2,6 +2,7 @@
>  
>  //! Additional numerical features for the kernel.
>  
> +use crate::const_assert;
>  use core::ops;

nit: commonly Rust code uses core/std -> dependency -> crate/super import
order (known as std/extern/crate order), so this would be

    use core::ops;

    use crate::const_assert;

under that order. But I don't think we require that (so no need to resend).

Best,
Gary