Re: [PATCH v6 05/14] rust: hrtimer: allow timer restart from timer handler

[Tamir Duberstein]

On Wed, Jan 15, 2025 at 6:21 AM Andreas Hindborg <a.hindborg@xxxxxxxxxx> wrote:
>
> "Tamir Duberstein" <tamird@xxxxxxxxx> writes:
>
> > On Fri, Jan 10, 2025 at 3:17 PM Andreas Hindborg <a.hindborg@xxxxxxxxxx> wrote:
> >>
> >> This patch allows timer handlers to report that they want a timer to be
> >> restarted after the timer handler has finished executing.
> >>
> >> Also update the `hrtimer` documentation to showcase the new feature.
> >>
> >> Signed-off-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx>
> >> ---
> >>  rust/kernel/time/hrtimer.rs     | 37 ++++++++++++++++++++++++++++++++++++-
> >>  rust/kernel/time/hrtimer/arc.rs |  4 +---
> >>  2 files changed, 37 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
> >> index d0842c7c4c6ddffeef9a79cbf9727819060e4333..50e8c23578b5cf7196893ac88d9547fc027f1f04 100644
> >> --- a/rust/kernel/time/hrtimer.rs
> >> +++ b/rust/kernel/time/hrtimer.rs
> >> @@ -167,7 +167,7 @@ pub trait HrTimerCallback {
> >>      type CallbackTargetParameter<'a>;
> >>
> >>      /// Called by the timer logic when the timer fires.
> >> -    fn run(this: Self::CallbackTargetParameter<'_>)
> >> +    fn run(this: Self::CallbackTargetParameter<'_>) -> HrTimerRestart
> >>      where
> >>          Self: Sized;
> >>  }
> >> @@ -262,6 +262,41 @@ unsafe fn start(self_ptr: *const Self, expires: Ktime) {
> >>      }
> >>  }
> >>
> >> +/// Restart policy for timers.
> >> +pub enum HrTimerRestart {
> >> +    /// Timer should not be restarted.
> >> +    NoRestart,
> >> +    /// Timer should be restarted.
> >> +    Restart,
> >> +}
> >> +
> >> +impl From<u32> for HrTimerRestart {
> >> +    fn from(value: u32) -> Self {
> >> +        match value {
> >> +            0 => Self::NoRestart,
> >> +            _ => Self::Restart,
> >> +        }
> >> +    }
> >> +}
> >> +
> >> +impl From<i32> for HrTimerRestart {
> >> +    fn from(value: i32) -> Self {
> >> +        match value {
> >> +            0 => Self::NoRestart,
> >> +            _ => Self::Restart,
> >> +        }
> >> +    }
> >> +}
> >
> > These are for converting from bindings to our enum, right? Why do we
> > need both signed and unsigned,
>
> Depending on kernel (target arch) configuration, the enum type will be
> either signed or unsigned on C side.
>
> I guess I could try to figure out what kernel configs effect the change
> and then do conditional compilation on Rust side, but it seems overkill.

The bindings seem to contain a type alias:

pub const hrtimer_restart_HRTIMER_NORESTART: hrtimer_restart = 0;
pub const hrtimer_restart_HRTIMER_RESTART: hrtimer_restart = 1;
pub type hrtimer_restart = ffi::c_uint;

Perhaps you could impl `From<bindings:: hrtimer_restart>` instead?

Tamir