time: allow storing state inside the driver struct.

embassy-nrf/src/time_driver.rs

@@ -82,7 +82,7 @@ impl AlarmState {
 
 const ALARM_COUNT: usize = 3;
 
-struct State {
+struct RtcDriver {
     /// Number of 2^23 periods elapsed since boot.
     period: AtomicU32,
     alarm_count: AtomicU8,
@@ -91,13 +91,13 @@ struct State {
 }
 
 const ALARM_STATE_NEW: AlarmState = AlarmState::new();
-static STATE: State = State {
+embassy::time_driver_impl!(static DRIVER: RtcDriver = RtcDriver {
     period: AtomicU32::new(0),
     alarm_count: AtomicU8::new(0),
     alarms: Mutex::new([ALARM_STATE_NEW; ALARM_COUNT]),
-};
+});
 
-impl State {
+impl RtcDriver {
     fn init(&'static self, irq_prio: crate::interrupt::Priority) {
         let r = rtc();
         r.cc[3].write(|w| unsafe { w.bits(0x800000) });
@@ -159,14 +159,6 @@ impl State {
         })
     }
 
-    fn now(&self) -> u64 {
-        // `period` MUST be read before `counter`, see comment at the top for details.
-        let period = self.period.load(Ordering::Relaxed);
-        compiler_fence(Ordering::Acquire);
-        let counter = rtc().counter.read().bits();
-        calc_now(period, counter)
-    }
-
     fn get_alarm<'a>(&'a self, cs: CriticalSection<'a>, alarm: AlarmHandle) -> &'a AlarmState {
         // safety: we're allowed to assume the AlarmState is created by us, and
         // we never create one that's out of bounds.
@@ -188,8 +180,18 @@ impl State {
         let f: fn(*mut ()) = unsafe { mem::transmute(alarm.callback.get()) };
         f(alarm.ctx.get());
     }
+}
 
-    fn allocate_alarm(&self) -> Option<AlarmHandle> {
+impl Driver for RtcDriver {
+    fn now(&self) -> u64 {
+        // `period` MUST be read before `counter`, see comment at the top for details.
+        let period = self.period.load(Ordering::Relaxed);
+        compiler_fence(Ordering::Acquire);
+        let counter = rtc().counter.read().bits();
+        calc_now(period, counter)
+    }
+
+    unsafe fn allocate_alarm(&self) -> Option<AlarmHandle> {
         let id = self
             .alarm_count
             .fetch_update(Ordering::AcqRel, Ordering::Acquire, |x| {
@@ -201,7 +203,7 @@ impl State {
             });
 
         match id {
-            Ok(id) => Some(unsafe { AlarmHandle::new(id) }),
+            Ok(id) => Some(AlarmHandle::new(id)),
             Err(_) => None,
         }
     }
@@ -263,32 +265,11 @@ impl State {
     }
 }
 
-struct RtcDriver;
-embassy::time_driver_impl!(RtcDriver);
-
-impl Driver for RtcDriver {
-    fn now() -> u64 {
-        STATE.now()
-    }
-
-    unsafe fn allocate_alarm() -> Option<AlarmHandle> {
-        STATE.allocate_alarm()
-    }
-
-    fn set_alarm_callback(alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ()) {
-        STATE.set_alarm_callback(alarm, callback, ctx)
-    }
-
-    fn set_alarm(alarm: AlarmHandle, timestamp: u64) {
-        STATE.set_alarm(alarm, timestamp)
-    }
-}
-
 #[interrupt]
 fn RTC1() {
-    STATE.on_interrupt()
+    DRIVER.on_interrupt()
 }
 
 pub(crate) fn init(irq_prio: crate::interrupt::Priority) {
-    STATE.init(irq_prio)
+    DRIVER.init(irq_prio)
 }

embassy-rp/src/timer.rs

@@ -19,10 +19,18 @@ const DUMMY_ALARM: AlarmState = AlarmState {
     callback: Cell::new(None),
 };
 
-static ALARMS: Mutex<[AlarmState; ALARM_COUNT]> = Mutex::new([DUMMY_ALARM; ALARM_COUNT]);
+struct TimerDriver {
-static NEXT_ALARM: AtomicU8 = AtomicU8::new(0);
+    alarms: Mutex<[AlarmState; ALARM_COUNT]>,
+    next_alarm: AtomicU8,
+}
 
-fn now() -> u64 {
+embassy::time_driver_impl!(static DRIVER: TimerDriver = TimerDriver{
+    alarms:  Mutex::new([DUMMY_ALARM; ALARM_COUNT]),
+    next_alarm: AtomicU8::new(0),
+});
+
+impl Driver for TimerDriver {
+    fn now(&self) -> u64 {
         loop {
             unsafe {
                 let hi = pac::TIMER.timerawh().read();
@@ -33,18 +41,12 @@ fn now() -> u64 {
                 }
             }
         }
-}
-
-struct TimerDriver;
-embassy::time_driver_impl!(TimerDriver);
-
-impl Driver for TimerDriver {
-    fn now() -> u64 {
-        now()
     }
 
-    unsafe fn allocate_alarm() -> Option<AlarmHandle> {
+    unsafe fn allocate_alarm(&self) -> Option<AlarmHandle> {
-        let id = NEXT_ALARM.fetch_update(Ordering::AcqRel, Ordering::Acquire, |x| {
+        let id = self
+            .next_alarm
+            .fetch_update(Ordering::AcqRel, Ordering::Acquire, |x| {
                 if x < ALARM_COUNT as u8 {
                     Some(x + 1)
                 } else {
@@ -58,18 +60,18 @@ impl Driver for TimerDriver {
         }
     }
 
-    fn set_alarm_callback(alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ()) {
+    fn set_alarm_callback(&self, alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ()) {
         let n = alarm.id() as usize;
         critical_section::with(|cs| {
-            let alarm = &ALARMS.borrow(cs)[n];
+            let alarm = &self.alarms.borrow(cs)[n];
             alarm.callback.set(Some((callback, ctx)));
         })
     }
 
-    fn set_alarm(alarm: AlarmHandle, timestamp: u64) {
+    fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) {
         let n = alarm.id() as usize;
         critical_section::with(|cs| {
-            let alarm = &ALARMS.borrow(cs)[n];
+            let alarm = &self.alarms.borrow(cs)[n];
             alarm.timestamp.set(timestamp);
 
             // Arm it.
@@ -78,23 +80,24 @@ impl Driver for TimerDriver {
             // it is checked if the alarm time has passed.
             unsafe { pac::TIMER.alarm(n).write_value(timestamp as u32) };
 
-            let now = now();
+            let now = self.now();
 
             // If alarm timestamp has passed, trigger it instantly.
             // This disarms it.
             if timestamp <= now {
-                trigger_alarm(n, cs);
+                self.trigger_alarm(n, cs);
             }
         })
     }
 }
 
-fn check_alarm(n: usize) {
+impl TimerDriver {
+    fn check_alarm(&self, n: usize) {
         critical_section::with(|cs| {
-        let alarm = &ALARMS.borrow(cs)[n];
+            let alarm = &self.alarms.borrow(cs)[n];
             let timestamp = alarm.timestamp.get();
-        if timestamp <= now() {
+            if timestamp <= self.now() {
-            trigger_alarm(n, cs)
+                self.trigger_alarm(n, cs)
             } else {
                 // Not elapsed, arm it again.
                 // This can happen if it was set more than 2^32 us in the future.
@@ -104,26 +107,27 @@ fn check_alarm(n: usize) {
 
         // clear the irq
         unsafe { pac::TIMER.intr().write(|w| w.set_alarm(n, true)) }
-}
+    }
 
-fn trigger_alarm(n: usize, cs: CriticalSection) {
+    fn trigger_alarm(&self, n: usize, cs: CriticalSection) {
         // disarm
         unsafe { pac::TIMER.armed().write(|w| w.set_armed(1 << n)) }
 
-    let alarm = &ALARMS.borrow(cs)[n];
+        let alarm = &self.alarms.borrow(cs)[n];
         alarm.timestamp.set(u64::MAX);
 
         // Call after clearing alarm, so the callback can set another alarm.
         if let Some((f, ctx)) = alarm.callback.get() {
             f(ctx);
         }
+    }
 }
 
 /// safety: must be called exactly once at bootup
 pub unsafe fn init() {
     // init alarms
     critical_section::with(|cs| {
-        let alarms = ALARMS.borrow(cs);
+        let alarms = DRIVER.alarms.borrow(cs);
         for a in alarms {
             a.timestamp.set(u64::MAX);
         }
@@ -144,20 +148,20 @@ pub unsafe fn init() {
 
 #[interrupt]
 unsafe fn TIMER_IRQ_0() {
-    check_alarm(0)
+    DRIVER.check_alarm(0)
 }
 
 #[interrupt]
 unsafe fn TIMER_IRQ_1() {
-    check_alarm(1)
+    DRIVER.check_alarm(1)
 }
 
 #[interrupt]
 unsafe fn TIMER_IRQ_2() {
-    check_alarm(2)
+    DRIVER.check_alarm(2)
 }
 
 #[interrupt]
 unsafe fn TIMER_IRQ_3() {
-    check_alarm(3)
+    DRIVER.check_alarm(3)
 }

embassy-stm32/src/time_driver.rs

@@ -26,12 +26,12 @@ type T = peripherals::TIM3;
 #[cfg(feature = "time-driver-tim2")]
 #[interrupt]
 fn TIM2() {
-    STATE.on_interrupt()
+    DRIVER.on_interrupt()
 }
 #[cfg(feature = "time-driver-tim3")]
 #[interrupt]
 fn TIM3() {
-    STATE.on_interrupt()
+    DRIVER.on_interrupt()
 }
 
 // Clock timekeeping works with something we call "periods", which are time intervals
@@ -76,7 +76,7 @@ impl AlarmState {
     }
 }
 
-struct State {
+struct RtcDriver {
     /// Number of 2^15 periods elapsed since boot.
     period: AtomicU32,
     alarm_count: AtomicU8,
@@ -85,13 +85,14 @@ struct State {
 }
 
 const ALARM_STATE_NEW: AlarmState = AlarmState::new();
-static STATE: State = State {
+
+embassy::time_driver_impl!(static DRIVER: RtcDriver = RtcDriver {
     period: AtomicU32::new(0),
     alarm_count: AtomicU8::new(0),
     alarms: Mutex::new([ALARM_STATE_NEW; ALARM_COUNT]),
-};
+});
 
-impl State {
+impl RtcDriver {
     fn init(&'static self) {
         let r = T::regs();
 
@@ -185,16 +186,6 @@ impl State {
         })
     }
 
-    fn now(&self) -> u64 {
-        let r = T::regs();
-
-        let period = self.period.load(Ordering::Relaxed);
-        compiler_fence(Ordering::Acquire);
-        // NOTE(unsafe) Atomic read with no side-effects
-        let counter = unsafe { r.cnt().read().cnt() };
-        calc_now(period, counter)
-    }
-
     fn get_alarm<'a>(&'a self, cs: CriticalSection<'a>, alarm: AlarmHandle) -> &'a AlarmState {
         // safety: we're allowed to assume the AlarmState is created by us, and
         // we never create one that's out of bounds.
@@ -213,8 +204,20 @@ impl State {
         let f: fn(*mut ()) = unsafe { mem::transmute(alarm.callback.get()) };
         f(alarm.ctx.get());
     }
+}
 
-    fn allocate_alarm(&self) -> Option<AlarmHandle> {
+impl Driver for RtcDriver {
+    fn now(&self) -> u64 {
+        let r = T::regs();
+
+        let period = self.period.load(Ordering::Relaxed);
+        compiler_fence(Ordering::Acquire);
+        // NOTE(unsafe) Atomic read with no side-effects
+        let counter = unsafe { r.cnt().read().cnt() };
+        calc_now(period, counter)
+    }
+
+    unsafe fn allocate_alarm(&self) -> Option<AlarmHandle> {
         let id = self
             .alarm_count
             .fetch_update(Ordering::AcqRel, Ordering::Acquire, |x| {
@@ -226,7 +229,7 @@ impl State {
             });
 
         match id {
-            Ok(id) => Some(unsafe { AlarmHandle::new(id) }),
+            Ok(id) => Some(AlarmHandle::new(id)),
             Err(_) => None,
         }
     }
@@ -269,29 +272,8 @@ impl State {
     }
 }
 
-struct RtcDriver;
-embassy::time_driver_impl!(RtcDriver);
-
-impl Driver for RtcDriver {
-    fn now() -> u64 {
-        STATE.now()
-    }
-
-    unsafe fn allocate_alarm() -> Option<AlarmHandle> {
-        STATE.allocate_alarm()
-    }
-
-    fn set_alarm_callback(alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ()) {
-        STATE.set_alarm_callback(alarm, callback, ctx)
-    }
-
-    fn set_alarm(alarm: AlarmHandle, timestamp: u64) {
-        STATE.set_alarm(alarm, timestamp)
-    }
-}
-
 pub(crate) fn init() {
-    STATE.init()
+    DRIVER.init()
 }
 
 // ------------------------------------------------------

embassy/src/executor/arch/std.rs

@@ -0,0 +1,67 @@
+use std::marker::PhantomData;
+use std::sync::{Condvar, Mutex};
+
+use super::{raw, Spawner};
+
+pub struct Executor {
+    inner: raw::Executor,
+    not_send: PhantomData<*mut ()>,
+    signaler: &'static Signaler,
+}
+
+impl Executor {
+    pub fn new() -> Self {
+        let signaler = &*Box::leak(Box::new(Signaler::new()));
+        Self {
+            inner: raw::Executor::new(
+                |p| unsafe {
+                    let s = &*(p as *const () as *const Signaler);
+                    s.signal()
+                },
+                signaler as *const _ as _,
+            ),
+            not_send: PhantomData,
+            signaler,
+        }
+    }
+
+    /// Runs the executor.
+    ///
+    /// This function never returns.
+    pub fn run(&'static mut self, init: impl FnOnce(Spawner)) -> ! {
+        init(unsafe { self.inner.spawner() });
+
+        loop {
+            unsafe { self.inner.run_queued() };
+            self.signaler.wait()
+        }
+    }
+}
+
+struct Signaler {
+    mutex: Mutex<bool>,
+    condvar: Condvar,
+}
+
+impl Signaler {
+    fn new() -> Self {
+        Self {
+            mutex: Mutex::new(false),
+            condvar: Condvar::new(),
+        }
+    }
+
+    fn wait(&self) {
+        let mut signaled = self.mutex.lock().unwrap();
+        while !*signaled {
+            signaled = self.condvar.wait(signaled).unwrap();
+        }
+        *signaled = false;
+    }
+
+    fn signal(&self) {
+        let mut signaled = self.mutex.lock().unwrap();
+        *signaled = true;
+        self.condvar.notify_one();
+    }
+}

embassy/src/time/driver.rs

@@ -26,32 +26,34 @@
 //! This method has a few key advantages for something as foundational as timekeeping:
 //!
 //! - The time driver is available everywhere easily, without having to thread the implementation
-//~   through generic parameters. This is especially helpful for libraries.
+//!   through generic parameters. This is especially helpful for libraries.
 //! - It means comparing `Instant`s will always make sense: if there were multiple drivers
 //!   active, one could compare an `Instant` from driver A to an `Instant` from driver B, which
 //!   would yield incorrect results.
 //!
-/// # Example
+//! # Example
-///
+//!
-/// ```
+//! ```
-/// struct MyDriver; // not public!
+//! use embassy::time::driver::{Driver, AlarmHandle};
-/// embassy::time_driver_impl!(MyDriver);
+//!
-///
+//! struct MyDriver{}; // not public!
-/// unsafe impl embassy::time::driver::Driver for MyDriver {
+//! embassy::time_driver_impl!(static DRIVER: MyDriver = MyDriver{});
-///     fn now() -> u64 {
+//!
-///         todo!()
+//! impl Driver for MyDriver {
-///     }
+//!     fn now(&self) -> u64 {
-///     unsafe fn allocate_alarm() -> Option<AlarmHandle> {
+//!         todo!()
-///         todo!()
+//!     }
-///     }
+//!     unsafe fn allocate_alarm(&self) -> Option<AlarmHandle> {
-///     fn set_alarm_callback(alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ()) {
+//!         todo!()
-///         todo!()
+//!     }
-///     }
+//!     fn set_alarm_callback(&self, alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ()) {
-///     fn set_alarm(alarm: AlarmHandle, timestamp: u64) {
+//!         todo!()
-///         todo!()
+//!     }
-///     }
+//!     fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64) {
-/// }
+//!         todo!()
-/// ```
+//!     }
+//! }
+//! ```
 
 /// Alarm handle, assigned by the driver.
 #[derive(Clone, Copy)]
@@ -76,22 +78,22 @@ impl AlarmHandle {
 }
 
 /// Time driver
-pub trait Driver {
+pub trait Driver: Send + Sync + 'static {
     /// Return the current timestamp in ticks.
     /// This is guaranteed to be monotonic, i.e. a call to now() will always return
     /// a greater or equal value than earler calls.
-    fn now() -> u64;
+    fn now(&self) -> u64;
 
     /// Try allocating an alarm handle. Returns None if no alarms left.
     /// Initially the alarm has no callback set, and a null `ctx` pointer.
     ///
     /// # Safety
     /// It is UB to make the alarm fire before setting a callback.
-    unsafe fn allocate_alarm() -> Option<AlarmHandle>;
+    unsafe fn allocate_alarm(&self) -> Option<AlarmHandle>;
 
     /// Sets the callback function to be called when the alarm triggers.
     /// The callback may be called from any context (interrupt or thread mode).
-    fn set_alarm_callback(alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ());
+    fn set_alarm_callback(&self, alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ());
 
     /// Sets an alarm at the given timestamp. When the current timestamp reaches that
     /// timestamp, the provided callback funcion will be called.
@@ -99,7 +101,7 @@ pub trait Driver {
     /// When callback is called, it is guaranteed that now() will return a value greater or equal than timestamp.
     ///
     /// Only one alarm can be active at a time. This overwrites any previously-set alarm if any.
-    fn set_alarm(alarm: AlarmHandle, timestamp: u64);
+    fn set_alarm(&self, alarm: AlarmHandle, timestamp: u64);
 }
 
 extern "Rust" {
@@ -125,49 +127,34 @@ pub(crate) fn set_alarm(alarm: AlarmHandle, timestamp: u64) {
 
 /// Set the time Driver implementation.
 ///
-/// # Example
+/// See the module documentation for an example.
-///
-/// ```
-/// struct MyDriver; // not public!
-/// embassy::time_driver_impl!(MyDriver);
-///
-/// unsafe impl embassy::time::driver::Driver for MyDriver {
-///     fn now() -> u64 {
-///         todo!()
-///     }
-///     unsafe fn allocate_alarm() -> Option<AlarmHandle> {
-///         todo!()
-///     }
-///     fn set_alarm_callback(alarm: AlarmHandle, callback: fn(*mut ()), ctx: *mut ()) {
-///         todo!()
-///     }
-///     fn set_alarm(alarm: AlarmHandle, timestamp: u64) {
-///         todo!()
-///     }
-/// }
-/// ```
 #[macro_export]
 macro_rules! time_driver_impl {
-    ($t: ty) => {
+    (static $name:ident: $t: ty = $val:expr) => {
+        static $name: $t = $val;
+
         #[no_mangle]
         fn _embassy_time_now() -> u64 {
-            <$t as $crate::time::driver::Driver>::now()
+            <$t as $crate::time::driver::Driver>::now(&$name)
         }
+
         #[no_mangle]
-        unsafe fn _embassy_time_allocate_alarm() -> Option<AlarmHandle> {
+        unsafe fn _embassy_time_allocate_alarm() -> Option<$crate::time::driver::AlarmHandle> {
-            <$t as $crate::time::driver::Driver>::allocate_alarm()
+            <$t as $crate::time::driver::Driver>::allocate_alarm(&$name)
         }
+
         #[no_mangle]
         fn _embassy_time_set_alarm_callback(
-            alarm: AlarmHandle,
+            alarm: $crate::time::driver::AlarmHandle,
             callback: fn(*mut ()),
             ctx: *mut (),
         ) {
-            <$t as $crate::time::driver::Driver>::set_alarm_callback(alarm, callback, ctx)
+            <$t as $crate::time::driver::Driver>::set_alarm_callback(&$name, alarm, callback, ctx)
         }
+
         #[no_mangle]
-        fn _embassy_time_set_alarm(alarm: AlarmHandle, timestamp: u64) {
+        fn _embassy_time_set_alarm(alarm: $crate::time::driver::AlarmHandle, timestamp: u64) {
-            <$t as $crate::time::driver::Driver>::set_alarm(alarm, timestamp)
+            <$t as $crate::time::driver::Driver>::set_alarm(&$name, alarm, timestamp)
         }
     };
 }