linux-kernel - Re: [PATCH v8 05/14] rust: hrtimer: allow timer restart from timer handler

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Message-ID: <7536dcf0-ed86-48ab-af35-bf86fcdc5601@proton.me>
Date: Fri, 21 Feb 2025 10:15:16 +0000
From: Benno Lossin <benno.lossin@...ton.me>
To: Andreas Hindborg <a.hindborg@...nel.org>
Cc: Miguel Ojeda <ojeda@...nel.org>, Anna-Maria Behnsen <anna-maria@...utronix.de>, Frederic Weisbecker <frederic@...nel.org>, Thomas Gleixner <tglx@...utronix.de>, Danilo Krummrich <dakr@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, Björn Roy Baron <bjorn3_gh@...tonmail.com>, Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, Lyude Paul <lyude@...hat.com>, Guangbo Cui <2407018371@...com>, Dirk Behme <dirk.behme@...il.com>, Daniel Almeida <daniel.almeida@...labora.com>, Tamir Duberstein <tamird@...il.com>, rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v8 05/14] rust: hrtimer: allow timer restart from timer handler

On 21.02.25 10:09, Andreas Hindborg wrote:
> "Benno Lossin" <benno.lossin@...ton.me> writes:
> 
>> On 18.02.25 14:27, Andreas Hindborg 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@...nel.org>
>>> ---
>>>  rust/kernel/time/hrtimer.rs     | 28 +++++++++++++++++++++++++++-
>>>  rust/kernel/time/hrtimer/arc.rs |  4 +---
>>>  2 files changed, 28 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/rust/kernel/time/hrtimer.rs b/rust/kernel/time/hrtimer.rs
>>> index b2a3130bc21d7..e342193f985eb 100644
>>> --- a/rust/kernel/time/hrtimer.rs
>>> +++ b/rust/kernel/time/hrtimer.rs
>>> @@ -183,7 +183,7 @@ 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;
>>>  }
>>> @@ -278,6 +278,32 @@ 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<bindings::hrtimer_restart> for HrTimerRestart {
>>> +    fn from(value: u32) -> Self {
>>> +        match value {
>>> +            bindings::hrtimer_restart_HRTIMER_NORESTART => Self::NoRestart,
>>> +            _ => Self::Restart,
>>> +        }
>>> +    }
>>> +}
>>> +
>>> +impl From<HrTimerRestart> for bindings::hrtimer_restart {
>>> +    fn from(value: HrTimerRestart) -> Self {
>>> +        match value {
>>> +            HrTimerRestart::NoRestart => bindings::hrtimer_restart_HRTIMER_NORESTART,
>>> +            HrTimerRestart::Restart => bindings::hrtimer_restart_HRTIMER_RESTART,
>>> +        }
>>> +    }
>>> +}
>>
>> Do drivers need these impls? If no, I would prefer a private conversion
>> function just for the abstraction.
> 
> No, drivers would not need these. I can hide them.

Sounds good, you can add:

Reviewed-by: Benno Lossin <benno.lossin@...ton.me>

---
Cheers,
Benno