netdev - Re: [PATCH v8 2/7] rust: time: Introduce Delta type

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Message-ID: <CAH5fLghAfovcm0ZJBByswXRSM4dRQY4ht7N7YGscWOaT+fN9OA@mail.gmail.com>
Date: Thu, 16 Jan 2025 10:36:07 +0100
From: Alice Ryhl <aliceryhl@...gle.com>
To: FUJITA Tomonori <fujita.tomonori@...il.com>
Cc: linux-kernel@...r.kernel.org, Andrew Lunn <andrew@...n.ch>, 
	rust-for-linux@...r.kernel.org, netdev@...r.kernel.org, hkallweit1@...il.com, 
	tmgross@...ch.edu, ojeda@...nel.org, alex.gaynor@...il.com, gary@...yguo.net, 
	bjorn3_gh@...tonmail.com, benno.lossin@...ton.me, a.hindborg@...sung.com, 
	anna-maria@...utronix.de, frederic@...nel.org, tglx@...utronix.de, 
	arnd@...db.de, jstultz@...gle.com, sboyd@...nel.org, mingo@...hat.com, 
	peterz@...radead.org, juri.lelli@...hat.com, vincent.guittot@...aro.org, 
	dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com, 
	mgorman@...e.de, vschneid@...hat.com
Subject: Re: [PATCH v8 2/7] rust: time: Introduce Delta type

On Thu, Jan 16, 2025 at 5:42 AM FUJITA Tomonori
<fujita.tomonori@...il.com> wrote:
>
> Introduce a type representing a span of time. Define our own type
> because `core::time::Duration` is large and could panic during
> creation.
>
> time::Ktime could be also used for time duration but timestamp and
> timedelta are different so better to use a new type.
>
> i64 is used instead of u64 to represent a span of time; some C drivers
> uses negative Deltas and i64 is more compatible with Ktime using i64
> too (e.g., ktime_[us|ms]_delta() APIs return i64 so we create Delta
> object without type conversion.
>
> i64 is used instead of bindings::ktime_t because when the ktime_t
> type is used as timestamp, it represents values from 0 to
> KTIME_MAX, which different from Delta.
>
> Delta::from_[millis|secs] APIs take i64. When a span of time
> overflows, i64::MAX is used.
>
> Reviewed-by: Andrew Lunn <andrew@...n.ch>
> Signed-off-by: FUJITA Tomonori <fujita.tomonori@...il.com>

One nit below, otherwise LGTM

Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>

> +    /// Return the number of nanoseconds in the `Delta`.
> +    #[inline]
> +    pub fn as_nanos(self) -> i64 {
> +        self.nanos
> +    }

I added the ktime_ms_delta() function because I was going to use it.
Can you add an `as_millis()` function too? That way I can use
start_time.elapsed().as_millis() for my use-case.

Alice