116 lines
3.7 KiB
Rust
116 lines
3.7 KiB
Rust
use core::cell::UnsafeCell;
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use core::marker::{PhantomData, PhantomPinned};
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use core::pin::Pin;
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use core::ptr;
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use embassy::interrupt::{Interrupt, InterruptExt};
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/// A version of `PeripheralState` without the `'static` bound,
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/// for cases where the compiler can't statically make sure
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/// that `on_interrupt` doesn't reference anything which might be invalidated.
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///
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/// # Safety
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/// When types implementing this trait are used with `PeripheralMutex`,
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/// no fields referenced by `on_interrupt`'s lifetimes must end without first calling `Drop` on the `PeripheralMutex`.
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pub unsafe trait PeripheralStateUnchecked: Send {
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type Interrupt: Interrupt;
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fn on_interrupt(&mut self);
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}
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/// A type which can be used as state with `PeripheralMutex`.
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///
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/// It needs to be `Send` because `&mut` references are sent back and forth between the 'thread' which owns the `PeripheralMutex` and the interrupt,
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/// and `&mut T` is `Send` where `T: Send`.
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///
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/// It also requires `'static`, because although `Pin` guarantees that the memory of the state won't be invalidated,
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/// it doesn't guarantee that the lifetime will last.
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pub trait PeripheralState: Send + 'static {
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type Interrupt: Interrupt;
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fn on_interrupt(&mut self);
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}
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// SAFETY: `T` has to live for `'static` to implement `PeripheralState`, thus its lifetime cannot end.
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unsafe impl<T> PeripheralStateUnchecked for T
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where
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T: PeripheralState,
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{
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type Interrupt = T::Interrupt;
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fn on_interrupt(&mut self) {
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self.on_interrupt()
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}
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}
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pub struct PeripheralMutex<S: PeripheralStateUnchecked> {
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state: UnsafeCell<S>,
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irq_setup_done: bool,
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irq: S::Interrupt,
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_not_send: PhantomData<*mut ()>,
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_pinned: PhantomPinned,
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}
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impl<S: PeripheralStateUnchecked> PeripheralMutex<S> {
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pub fn new(state: S, irq: S::Interrupt) -> Self {
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Self {
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irq,
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irq_setup_done: false,
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state: UnsafeCell::new(state),
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_not_send: PhantomData,
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_pinned: PhantomPinned,
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}
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}
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pub fn register_interrupt(self: Pin<&mut Self>) {
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let this = unsafe { self.get_unchecked_mut() };
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if this.irq_setup_done {
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return;
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}
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this.irq.disable();
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this.irq.set_handler(|p| {
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critical_section::with(|_| {
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if p.is_null() {
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// The state was dropped, so we can't operate on it.
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return;
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}
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// Safety: it's OK to get a &mut to the state, since
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// - We're in a critical section, no one can preempt us (and call with())
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// - We can't have preempted a with() call because the irq is disabled during it.
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let state = unsafe { &mut *(p as *mut S) };
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state.on_interrupt();
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})
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});
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this.irq
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.set_handler_context((&mut this.state) as *mut _ as *mut ());
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this.irq.enable();
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this.irq_setup_done = true;
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}
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pub fn with<R>(self: Pin<&mut Self>, f: impl FnOnce(&mut S, &mut S::Interrupt) -> R) -> R {
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let this = unsafe { self.get_unchecked_mut() };
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this.irq.disable();
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// Safety: it's OK to get a &mut to the state, since the irq is disabled.
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let state = unsafe { &mut *this.state.get() };
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let r = f(state, &mut this.irq);
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this.irq.enable();
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r
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}
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}
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impl<S: PeripheralStateUnchecked> Drop for PeripheralMutex<S> {
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fn drop(&mut self) {
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self.irq.disable();
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self.irq.remove_handler();
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// Set the context to null so that the interrupt will know we're dropped
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// if we pre-empted it before it entered a critical section.
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self.irq.set_handler_context(ptr::null_mut());
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}
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}
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