linux-kernel - Re: [PATCH v1] rust: time: Add examples with doctest for Delta

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Message-ID: <874ivvvvjw.fsf@kernel.org>
Date: Wed, 02 Jul 2025 10:36:19 +0200
From: Andreas Hindborg <a.hindborg@...nel.org>
To: "FUJITA Tomonori" <fujita.tomonori@...il.com>
Cc: <alex.gaynor@...il.com>,  <ojeda@...nel.org>,  <aliceryhl@...gle.com>,
  <anna-maria@...utronix.de>,  <bjorn3_gh@...tonmail.com>,
  <boqun.feng@...il.com>,  <dakr@...nel.org>,  <frederic@...nel.org>,
  <gary@...yguo.net>,  <jstultz@...gle.com>,
  <linux-kernel@...r.kernel.org>,  <lossin@...nel.org>,
  <lyude@...hat.com>,  <rust-for-linux@...r.kernel.org>,
  <sboyd@...nel.org>,  <tglx@...utronix.de>,  <tmgross@...ch.edu>
Subject: Re: [PATCH v1] rust: time: Add examples with doctest for Delta

"FUJITA Tomonori" <fujita.tomonori@...il.com> writes:

> Add examples with doctest for Delta methods and associated
> functions. These examples explicitly test overflow and saturation
> behavior.
>
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@...il.com>
> ---
>  rust/kernel/time.rs | 67 +++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 67 insertions(+)
>
> diff --git a/rust/kernel/time.rs b/rust/kernel/time.rs
> index 64c8dcf548d6..c6322275115a 100644
> --- a/rust/kernel/time.rs
> +++ b/rust/kernel/time.rs
> @@ -228,11 +228,34 @@ impl Delta {
>      /// A span of time equal to zero.
>      pub const ZERO: Self = Self { nanos: 0 };
>
> +    /// Create a new [`Delta`] from a number of nanoseconds.
> +    ///
> +    /// The `nanos` can range from [`i64::MIN`] to [`i64::MAX`].
> +    #[inline]
> +    pub const fn from_nanos(nanos: i64) -> Self {
> +        Self { nanos }
> +    }
> +
>      /// Create a new [`Delta`] from a number of microseconds.
>      ///
>      /// The `micros` can range from -9_223_372_036_854_775 to 9_223_372_036_854_775.
>      /// If `micros` is outside this range, `i64::MIN` is used for negative values,
>      /// and `i64::MAX` is used for positive values due to saturation.
> +    ///
> +    /// # Examples
> +    ///
> +    /// ```
> +    /// let delta = kernel::time::Delta::from_micros(5);
> +    /// assert_eq!(delta.as_nanos(), 5_000);
> +    /// let delta = kernel::time::Delta::from_micros(9_223_372_036_854_775);
> +    /// assert_eq!(delta.as_nanos(), 9_223_372_036_854_775_000);
> +    /// let delta = kernel::time::Delta::from_micros(9_223_372_036_854_776);
> +    /// assert_eq!(delta.as_nanos(), i64::MAX);
> +    /// let delta = kernel::time::Delta::from_micros(-9_223_372_036_854_775);
> +    /// assert_eq!(delta.as_nanos(), -9_223_372_036_854_775_000);
> +    /// let delta = kernel::time::Delta::from_micros(-9_223_372_036_854_776);
> +    /// assert_eq!(delta.as_nanos(), i64::MIN);
> +    /// ```


I think this kind of test would be better suited for the new `#[test]`
macro. Would you agree?


Best regards,
Andreas Hindborg