Re: [PATCH v3 2/2] rust: use Delta and a Jiffies newtype for timeouts and delays

On Tue, Jul 21, 2026 at 2:57 AM FUJITA Tomonori <[email protected]> wrote:
> On Mon, 20 Jul 2026 11:16:06 -0700
> John Stultz <[email protected]> wrote:
>
> > On Mon, Jul 20, 2026 at 2:48 AM FUJITA Tomonori <[email protected]> wrote:
> >> On Sat, 18 Jul 2026 16:20:10 +0100
> >> "Gary Guo" <[email protected]> wrote:
> >> > I wonder if we should have time types being generic over units. So you can have
> >> > `Delta<Nsec>` and `Delta<Jiffy>` and `Instant<Nsec>`, `Instant<Jiffy>`, with the
> >> > generic default being set to `Nsec`.
> >> >
> >> >     Delta::new(42) // Delta<Nsec>
> >> >     Delta::new_jiffies(42) // Delta<Jiffy>
> >> >
> >> > Thoughts?
> >>
> >> I think making Delta generic over the time unit makes sense; Delta
> >> <Nsec> and Delta<Jiffy>.
> >>
> >> However, I don't think making Instant generic over the time unit is a
> >> good idea, even though it clearly is for Delta.
> >>
> >> Instant is already generic over ClockSource, and jiffies is not a
> >> clock source: it has no clockid_t, it is read via get_jiffies_64()
> >> rather than ktime_get(), and it cannot be armed through hrtimer. That
> >> leaves two ways to force a jiffies Instant, both looks wrong:
> >
> > I read the above and thought, "but jiffies is a clocksource":
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/kernel/time/jiffies.c#n21
> >
> > And then I realized there has been some unfortunate naming overlap,
> > where it seems the rust ClockSource seems to map to the clockid_t, not
> > to the clocksource concept that Linux uses to abstract the hardware
> > counter used as a source of time (for the majority of the clockids).
> >
> > Very much a bikeshed request, but is it too late to rename this to
> > ClockID or something? So there is maybe less confusion when reading
> > across C and Rust code?
>
> Ah, I misunderstood. Thanks for the pointer!
>
> You're right; the trait carries the clockid_t, not the hardware
> clocksource. It's not too late at all; I'll rename ClockSource to
> ClockId.

Sounds good. Thank you for the consideration!
-john