pin.rs

  1// SPDX-License-Identifier: GPL-2.0
  2
  3use super::HasHrTimer;
  4use super::HrTimer;
  5use super::HrTimerCallback;
  6use super::HrTimerCallbackContext;
  7use super::HrTimerHandle;
  8use super::HrTimerMode;
  9use super::RawHrTimerCallback;
 10use super::UnsafeHrTimerPointer;
 11use core::pin::Pin;
 12
 13/// A handle for a `Pin<&HasHrTimer>`. When the handle exists, the timer might be
 14/// running.
 15pub struct PinHrTimerHandle<'a, T>
 16where
 17    T: HasHrTimer<T>,
 18{
 19    pub(crate) inner: Pin<&'a T>,
 20}
 21
 22// SAFETY: We cancel the timer when the handle is dropped. The implementation of
 23// the `cancel` method will block if the timer handler is running.
 24unsafe impl<'a, T> HrTimerHandle for PinHrTimerHandle<'a, T>
 25where
 26    T: HasHrTimer<T>,
 27{
 28    fn cancel(&mut self) -> bool {
 29        let self_ptr: *const T = self.inner.get_ref();
 30
 31        // SAFETY: As we got `self_ptr` from a reference above, it must point to
 32        // a valid `T`.
 33        let timer_ptr = unsafe { <T as HasHrTimer<T>>::raw_get_timer(self_ptr) };
 34
 35        // SAFETY: As `timer_ptr` is derived from a reference, it must point to
 36        // a valid and initialized `HrTimer`.
 37        unsafe { HrTimer::<T>::raw_cancel(timer_ptr) }
 38    }
 39}
 40
 41impl<'a, T> Drop for PinHrTimerHandle<'a, T>
 42where
 43    T: HasHrTimer<T>,
 44{
 45    fn drop(&mut self) {
 46        self.cancel();
 47    }
 48}
 49
 50// SAFETY: We capture the lifetime of `Self` when we create a `PinHrTimerHandle`,
 51// so `Self` will outlive the handle.
 52unsafe impl<'a, T> UnsafeHrTimerPointer for Pin<&'a T>
 53where
 54    T: Send + Sync,
 55    T: HasHrTimer<T>,
 56    T: HrTimerCallback<Pointer<'a> = Self>,
 57{
 58    type TimerMode = <T as HasHrTimer<T>>::TimerMode;
 59    type TimerHandle = PinHrTimerHandle<'a, T>;
 60
 61    unsafe fn start(
 62        self,
 63        expires: <<T as HasHrTimer<T>>::TimerMode as HrTimerMode>::Expires,
 64    ) -> Self::TimerHandle {
 65        // Cast to pointer
 66        let self_ptr: *const T = self.get_ref();
 67
 68        // SAFETY:
 69        //  - As we derive `self_ptr` from a reference above, it must point to a
 70        //    valid `T`.
 71        //  - We keep `self` alive by wrapping it in a handle below.
 72        unsafe { T::start(self_ptr, expires) };
 73
 74        PinHrTimerHandle { inner: self }
 75    }
 76}
 77
 78impl<'a, T> RawHrTimerCallback for Pin<&'a T>
 79where
 80    T: HasHrTimer<T>,
 81    T: HrTimerCallback<Pointer<'a> = Self>,
 82{
 83    type CallbackTarget<'b> = Self;
 84
 85    unsafe extern "C" fn run(ptr: *mut bindings::hrtimer) -> bindings::hrtimer_restart {
 86        // `HrTimer` is `repr(C)`
 87        let timer_ptr = ptr.cast::<HrTimer<T>>();
 88
 89        // SAFETY: By the safety requirement of this function, `timer_ptr`
 90        // points to a `HrTimer<T>` contained in an `T`.
 91        let receiver_ptr = unsafe { T::timer_container_of(timer_ptr) };
 92
 93        // SAFETY:
 94        //  - By the safety requirement of this function, `timer_ptr`
 95        //    points to a `HrTimer<T>` contained in an `T`.
 96        //  - As per the safety requirements of the trait `HrTimerHandle`, the
 97        //    `PinHrTimerHandle` associated with this timer is guaranteed to
 98        //    be alive until this method returns. That handle borrows the `T`
 99        //    behind `receiver_ptr`, thus guaranteeing the validity of
100        //    the reference created below.
101        let receiver_ref = unsafe { &*receiver_ptr };
102
103        // SAFETY: `receiver_ref` only exists as pinned, so it is safe to pin it
104        // here.
105        let receiver_pin = unsafe { Pin::new_unchecked(receiver_ref) };
106
107        // SAFETY:
108        // - By C API contract `timer_ptr` is the pointer that we passed when queuing the timer, so
109        //   it is a valid pointer to a `HrTimer<T>` embedded in a `T`.
110        // - We are within `RawHrTimerCallback::run`
111        let context = unsafe { HrTimerCallbackContext::from_raw(timer_ptr) };
112
113        T::run(receiver_pin, context).into_c()
114    }
115}