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

[Andreas Hindborg <a.hindborg@kernel.org>]

"Tamir Duberstein" <tamird@gmail.com> writes:

> On Wed, Jan 15, 2025 at 6:21 AM Andreas Hindborg <a.hindborg@kernel.org> wrote:
>>
>> "Tamir Duberstein" <tamird@gmail.com> writes:
>>
>> > On Fri, Jan 10, 2025 at 3:17 PM Andreas Hindborg <a.hindborg@kernel.org> 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@kernel.org>
>> >> ---
>> >>  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?

Yes - good idea!


Best regards,
Andreas Hindborg