Merge #613

613: Rust stable support r=Dirbaio a=Dirbaio

This PR adds (limited) stable Rust support!

The drawbacks are: 

- No `#[embassy::task]`, `#[embassy::main]`. (requires `type_alias_impl_trait`). You have to manually allocate the tasks somewhere they'll live forever. See [example](https://github.com/embassy-rs/embassy/blob/master/examples/nrf/src/bin/raw_spawn.rs)
- No async trait impls (requires GATs). Note that the full API surface of HALs is still available through inherent methods: #552 #581 
- Some stuff is not constructible in const (requires `const_fn_trait_bound`), although there's an (ugly) workaround for the generic `Mutex`.

So it's not that bad in the end, it's fully usable for shipping production-ready firmwares. We'll still recommend nightly as the default, until GATs and `type_alias_impl_trait` are stable.

Co-authored-by: Dario Nieuwenhuis <dirbaio@dirbaio.net>

embassy-nrf/src/gpiote.rs

@@ -463,7 +463,6 @@ mod eh02 {
 #[cfg(feature = "unstable-traits")]
 mod eh1 {
     use super::*;
-    use futures::FutureExt;
 
     impl<'d, C: Channel, T: GpioPin> embedded_hal_1::digital::ErrorType for InputChannel<'d, C, T> {
         type Error = Infallible;
@@ -480,6 +479,12 @@ mod eh1 {
             self.pin.is_low()
         }
     }
+}
+
+#[cfg(all(feature = "unstable-traits", feature = "nightly"))]
+mod eh1a {
+    use super::*;
+    use futures::FutureExt;
 
     impl<'d, T: GpioPin> embedded_hal_async::digital::Wait for Input<'d, T> {
         type WaitForHighFuture<'a>

embassy-nrf/src/lib.rs

@@ -1,6 +1,8 @@
 #![no_std]
-#![feature(generic_associated_types)]
-#![feature(type_alias_impl_trait)]
+#![cfg_attr(
+    feature = "nightly",
+    feature(generic_associated_types, type_alias_impl_trait)
+)]
 
 #[cfg(not(any(
     feature = "nrf51",

embassy-nrf/src/spim.rs

@@ -374,7 +374,6 @@ mod eh02 {
 #[cfg(feature = "unstable-traits")]
 mod eh1 {
     use super::*;
-    use core::future::Future;
 
     impl embedded_hal_1::spi::Error for Error {
         fn kind(&self) -> embedded_hal_1::spi::ErrorKind {
@@ -437,7 +436,7 @@ mod eh1 {
 
         fn transaction<'a>(
             &mut self,
-            operations: &mut [embedded_hal_async::spi::Operation<'a, u8>],
+            operations: &mut [embedded_hal_1::spi::blocking::Operation<'a, u8>],
         ) -> Result<(), Self::Error> {
             use embedded_hal_1::spi::blocking::Operation;
             for o in operations {
@@ -451,6 +450,12 @@ mod eh1 {
             Ok(())
         }
     }
+}
+
+#[cfg(all(feature = "unstable-traits", feature = "nightly"))]
+mod eh1a {
+    use super::*;
+    use core::future::Future;
 
     impl<'d, T: Instance> embedded_hal_async::spi::Read<u8> for Spim<'d, T> {
         type ReadFuture<'a>

embassy-nrf/src/time_driver.rs

@@ -2,6 +2,7 @@ use core::cell::Cell;
 use core::sync::atomic::{compiler_fence, AtomicU32, AtomicU8, Ordering};
 use core::{mem, ptr};
 use critical_section::CriticalSection;
+use embassy::blocking_mutex::raw::CriticalSectionRawMutex;
 use embassy::blocking_mutex::CriticalSectionMutex as Mutex;
 use embassy::interrupt::{Interrupt, InterruptExt};
 use embassy::time::driver::{AlarmHandle, Driver};
@@ -94,7 +95,7 @@ const ALARM_STATE_NEW: AlarmState = AlarmState::new();
 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]),
+    alarms: Mutex::const_new(CriticalSectionRawMutex::new(), [ALARM_STATE_NEW; ALARM_COUNT]),
 });
 
 impl RtcDriver {

embassy-nrf/src/twim.rs

@@ -679,7 +679,7 @@ mod eh1 {
         fn transaction<'a>(
             &mut self,
             _address: u8,
-            _operations: &mut [embedded_hal_async::i2c::Operation<'a>],
+            _operations: &mut [embedded_hal_1::i2c::blocking::Operation<'a>],
         ) -> Result<(), Self::Error> {
             todo!();
         }
@@ -690,58 +690,59 @@ mod eh1 {
             _operations: O,
         ) -> Result<(), Self::Error>
         where
-            O: IntoIterator<Item = embedded_hal_async::i2c::Operation<'a>>,
+            O: IntoIterator<Item = embedded_hal_1::i2c::blocking::Operation<'a>>,
         {
             todo!();
         }
     }
+}
 
-    impl<'d, T: Instance> embedded_hal_async::i2c::I2c for Twim<'d, T> {
-        type ReadFuture<'a>
-        where
-            Self: 'a,
-        = impl Future<Output = Result<(), Self::Error>> + 'a;
+#[cfg(all(feature = "unstable-traits", feature = "nightly"))]
+impl<'d, T: Instance> embedded_hal_async::i2c::I2c for Twim<'d, T> {
+    type ReadFuture<'a>
+    where
+        Self: 'a,
+    = impl Future<Output = Result<(), Self::Error>> + 'a;
 
-        fn read<'a>(&'a mut self, address: u8, buffer: &'a mut [u8]) -> Self::ReadFuture<'a> {
-            self.read(address, buffer)
-        }
+    fn read<'a>(&'a mut self, address: u8, buffer: &'a mut [u8]) -> Self::ReadFuture<'a> {
+        self.read(address, buffer)
+    }
 
-        type WriteFuture<'a>
-        where
-            Self: 'a,
-        = impl Future<Output = Result<(), Self::Error>> + 'a;
+    type WriteFuture<'a>
+    where
+        Self: 'a,
+    = impl Future<Output = Result<(), Self::Error>> + 'a;
 
-        fn write<'a>(&'a mut self, address: u8, bytes: &'a [u8]) -> Self::WriteFuture<'a> {
-            self.write(address, bytes)
-        }
+    fn write<'a>(&'a mut self, address: u8, bytes: &'a [u8]) -> Self::WriteFuture<'a> {
+        self.write(address, bytes)
+    }
 
-        type WriteReadFuture<'a>
-        where
-            Self: 'a,
-        = impl Future<Output = Result<(), Self::Error>> + 'a;
+    type WriteReadFuture<'a>
+    where
+        Self: 'a,
+    = impl Future<Output = Result<(), Self::Error>> + 'a;
 
-        fn write_read<'a>(
-            &'a mut self,
-            address: u8,
-            wr_buffer: &'a [u8],
-            rd_buffer: &'a mut [u8],
-        ) -> Self::WriteReadFuture<'a> {
-            self.write_read(address, wr_buffer, rd_buffer)
-        }
+    fn write_read<'a>(
+        &'a mut self,
+        address: u8,
+        wr_buffer: &'a [u8],
+        rd_buffer: &'a mut [u8],
+    ) -> Self::WriteReadFuture<'a> {
+        self.write_read(address, wr_buffer, rd_buffer)
+    }
 
-        type TransactionFuture<'a>
-        where
-            Self: 'a,
-        = impl Future<Output = Result<(), Self::Error>> + 'a;
+    type TransactionFuture<'a>
+    where
+        Self: 'a,
+    = impl Future<Output = Result<(), Self::Error>> + 'a;
 
-        fn transaction<'a>(
-            &'a mut self,
-            address: u8,
-            operations: &mut [embedded_hal_async::i2c::Operation<'a>],
-        ) -> Self::TransactionFuture<'a> {
-            let _ = address;
-            let _ = operations;
-            async move { todo!() }
-        }
+    fn transaction<'a>(
+        &'a mut self,
+        address: u8,
+        operations: &mut [embedded_hal_async::i2c::Operation<'a>],
+    ) -> Self::TransactionFuture<'a> {
+        let _ = address;
+        let _ = operations;
+        async move { todo!() }
     }
 }

embassy-nrf/src/uarte.rs

@@ -844,7 +844,6 @@ mod eh02 {
 #[cfg(feature = "unstable-traits")]
 mod eh1 {
     use super::*;
-    use core::future::Future;
 
     impl embedded_hal_1::serial::Error for Error {
         fn kind(&self) -> embedded_hal_1::serial::ErrorKind {
@@ -872,6 +871,36 @@ mod eh1 {
         }
     }
 
+    impl<'d, T: Instance> embedded_hal_1::serial::ErrorType for UarteTx<'d, T> {
+        type Error = Error;
+    }
+
+    impl<'d, T: Instance> embedded_hal_1::serial::blocking::Write for UarteTx<'d, T> {
+        fn write(&mut self, buffer: &[u8]) -> Result<(), Self::Error> {
+            self.blocking_write(buffer)
+        }
+
+        fn flush(&mut self) -> Result<(), Self::Error> {
+            Ok(())
+        }
+    }
+
+    impl<'d, T: Instance> embedded_hal_1::serial::ErrorType for UarteRx<'d, T> {
+        type Error = Error;
+    }
+
+    impl<'d, U: Instance, T: TimerInstance> embedded_hal_1::serial::ErrorType
+        for UarteWithIdle<'d, U, T>
+    {
+        type Error = Error;
+    }
+}
+
+#[cfg(all(feature = "unstable-traits", feature = "nightly"))]
+mod eh1a {
+    use super::*;
+    use core::future::Future;
+
     impl<'d, T: Instance> embedded_hal_async::serial::Read for Uarte<'d, T> {
         type ReadFuture<'a>
         where
@@ -903,22 +932,6 @@ mod eh1 {
         }
     }
 
-    // =====================
-
-    impl<'d, T: Instance> embedded_hal_1::serial::ErrorType for UarteTx<'d, T> {
-        type Error = Error;
-    }
-
-    impl<'d, T: Instance> embedded_hal_1::serial::blocking::Write for UarteTx<'d, T> {
-        fn write(&mut self, buffer: &[u8]) -> Result<(), Self::Error> {
-            self.blocking_write(buffer)
-        }
-
-        fn flush(&mut self) -> Result<(), Self::Error> {
-            Ok(())
-        }
-    }
-
     impl<'d, T: Instance> embedded_hal_async::serial::Write for UarteTx<'d, T> {
         type WriteFuture<'a>
         where
@@ -939,12 +952,6 @@ mod eh1 {
         }
     }
 
-    // =====================
-
-    impl<'d, T: Instance> embedded_hal_1::serial::ErrorType for UarteRx<'d, T> {
-        type Error = Error;
-    }
-
     impl<'d, T: Instance> embedded_hal_async::serial::Read for UarteRx<'d, T> {
         type ReadFuture<'a>
         where
@@ -956,14 +963,6 @@ mod eh1 {
         }
     }
 
-    // =====================
-
-    impl<'d, U: Instance, T: TimerInstance> embedded_hal_1::serial::ErrorType
-        for UarteWithIdle<'d, U, T>
-    {
-        type Error = Error;
-    }
-
     impl<'d, U: Instance, T: TimerInstance> embedded_hal_async::serial::Read
         for UarteWithIdle<'d, U, T>
     {