On Mon Aug 4, 2025 at 11:37 PM JST, Daniel Almeida wrote: > Hi Alex, > >> On 4 Aug 2025, at 08:45, Alexandre Courbot <acour...@nvidia.com> wrote: >> >> Rust provides traits for standard arithmetic and logic operations, but >> in the context of the kernel we often need to consider overflows. The >> checked Rust arithmetic methods are unfortunately not behind a trait, >> which makes them unavailable to generic code. >> >> As a start, add the `CheckedAdd` trait providing the `checked_add` >> operation and implement it for all integer types. Its name and location >> are inspired by the user-space `num` crate. >> >> This trait is to be first used by the `Alignment` type. >> >> Signed-off-by: Alexandre Courbot <acour...@nvidia.com> >> --- >> rust/kernel/lib.rs | 1 + >> rust/kernel/num.rs | 28 ++++++++++++++++++++++++++++ >> 2 files changed, 29 insertions(+) >> >> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs >> index >> 6b4774b2b1c37f4da1866e993be6230bc6715841..2955f65da1278dd4cba1e4272ff178b8211a892c >> 100644 >> --- a/rust/kernel/lib.rs >> +++ b/rust/kernel/lib.rs >> @@ -89,6 +89,7 @@ >> pub mod mm; >> #[cfg(CONFIG_NET)] >> pub mod net; >> +pub mod num; >> pub mod of; >> #[cfg(CONFIG_PM_OPP)] >> pub mod opp; >> diff --git a/rust/kernel/num.rs b/rust/kernel/num.rs >> new file mode 100644 >> index >> 0000000000000000000000000000000000000000..c81bb046078b70c321dd52aa9c2b5518be49d249 >> --- /dev/null >> +++ b/rust/kernel/num.rs >> @@ -0,0 +1,28 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> + >> +//! Numerical and binary utilities for primitive types. >> + >> +use core::ops::Add; >> + >> +/// Trait for performing a checked addition that returns `None` if the >> operation would overflow. > > nit: this can be [`None`] instead, which will let users click on it in the > docs. > > This is of course pretty frivolous.
... but correct. Thanks. > >> +/// >> +/// This trait exists in order to represent scalar types already having a >> `checked_add` method in >> +/// generic code. > > Maybe “scalar types that already have a `checked_add` method? > > But overall I feel like the whole sentence is a bit hard to parse, JFYI. Let me rephrase this as "This trait exists to model scalar types with a `checked_add` method in generic code." (provided this trait survives the next revision).
