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

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Message-Id: <20250704.093618.1554080777023438310.fujita.tomonori@gmail.com>
Date: Fri, 04 Jul 2025 09:36:18 +0900 (JST)
From: FUJITA Tomonori <fujita.tomonori@...il.com>
To: miguel.ojeda.sandonis@...il.com, a.hindborg@...nel.org
Cc: fujita.tomonori@...il.com, 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

On Wed, 2 Jul 2025 14:22:48 +0200
Miguel Ojeda <miguel.ojeda.sandonis@...il.com> wrote:

> On Wed, Jul 2, 2025 at 10:36 AM Andreas Hindborg <a.hindborg@...nel.org> wrote:
>>
>> I think this kind of test would be better suited for the new `#[test]`
>> macro. Would you agree?
> 
> I don't mind seeing the edge cases, since the behavior is mentioned in
> the docs, just like sometimes we show e.g. the `Err`/`None` cases in
> other functions etc., and it may help to further highlight that this
> can actually return possibly unexpected values.
> 
> It is also what the standard library does, at least in some similar cases, e.g.
> 
>     https://doc.rust-lang.org/std/primitive.i64.html#method.saturating_add
> 
> Maybe instead we can help making it a bit more readable, e.g. avoiding
> the intermediate variable to have a single line plus using a `# use
> Delta` to further reduce the line length?
> 
> Also adding a newline between the "normal" case and the saturation
> cases would probably help too.

I've updated from_micros() based on the above suggestion - looks
better to me. What do you think?

/// # Examples
///
/// ```
/// use kernel::time::Delta;
///
/// assert_eq!(Delta::from_micros(5).as_nanos(), 5_000);
/// assert_eq!(Delta::from_micros(9_223_372_036_854_775).as_nanos(), 9_223_372_036_854_775_000);
/// assert_eq!(Delta::from_micros(-9_223_372_036_854_775).as_nanos(), -9_223_372_036_854_775_000);
///
/// assert_eq!(Delta::from_micros(9_223_372_036_854_776).as_nanos(), i64::MAX);
/// assert_eq!(Delta::from_micros(-9_223_372_036_854_776).as_nanos(), i64::MIN);
/// ```
#[inline]
pub const fn from_micros(micros: i64) -> Self {
    Self {
        nanos: micros.saturating_mul(NSEC_PER_USEC),
    }
}