Re: [PATCH v8 02/14] rust: hrtimer: introduce hrtimer support

[Benno Lossin <benno.lossin@proton.me>]

On 21.02.25 11:15, Andreas Hindborg wrote:
> Andreas Hindborg <a.hindborg@kernel.org> writes:
> 
>> "Benno Lossin" <benno.lossin@proton.me> writes:
>>
>>> On 18.02.25 14:27, Andreas Hindborg wrote:
>>>> +pub trait HrTimerCallback {
>>>> +    /// The type whose [`RawHrTimerCallback::run`] method will be invoked when
>>>> +    /// the timer expires.
>>>> +    type CallbackTarget<'a>: RawHrTimerCallback;
>>>> +
>>>> +    /// This type is passed to the timer callback function. It may be a borrow
>>>> +    /// of [`Self::CallbackTarget`], or it may be `Self::CallbackTarget` if the
>>>> +    /// implementation can guarantee exclusive access to the target during timer
>>>
>>> Technically "exclusive" access is correct if the `CallbackTarget` is
>>> `Pin<&Self>`, since you will get exclusive access to a `Pin<&Self>`, but
>>> it might confuse people, because there can be multiple `Pin<&Self>`. So
>>> I would just drop the word "exclusive" here.
>>
>> Yes, maybe it should be "shared or exclusive access, depending on the type"?
>>
>>>
>>>> +    /// handler execution.
>>>> +    type CallbackTargetParameter<'a>;
>>>
>>> Also why can't this type be an associated type of `HrTimerPointer`?
>>> Since this seems to always be constrained in the impls of
>>> `RawHrTimerCallback`.
>>
>> That might be a nice improvement, I'll try that out.
> 
> Looking closer at this, I don't see how to achieve this. We need access
> to the type here, because it is used in the signature of `run`.
> `HrTimerCallback` has no bounds on it, and that is nice. If we want to
> move these associated types, we have to introduce a bound here.
> 
> We need to be generic over the type of the parameter to `run`, and by
> the time the user implements this trait, the type must be known and so
> the user has to specify somehow.

I think if you put the associated type on the `RawHrTimerCallback`
trait, it should work.

---
Cheers,
Benno