Merge #545

545: Add adapter for implementing async traits for blocking types r=lulf a=lulf

This allows writing drivers relying on async traits, while still
functioning with implementations that already implement the embedded-hal
traits.

Co-authored-by: Ulf Lilleengen <[email protected]>

2 files changed, 167 insertions, 0 deletions

diff --git a/embassy-traits/src/adapter.rs b/embassy-traits/src/adapter.rs
new file mode 100644
index 000000000..ce7dd411f
--- /dev/null
+++ b/embassy-traits/src/adapter.rs
@@ -0,0 +1,166 @@
+use core::future::Future;
+use embedded_hal::blocking;
+use embedded_hal::serial;
+
+/// BlockingAsync is a wrapper that implements async traits using blocking peripherals. This allows
+/// driver writers to depend on the async traits while still supporting embedded-hal peripheral implementations.
+///
+/// BlockingAsync will implement any async trait that maps to embedded-hal traits implemented for the wrapped driver.
+///
+/// Driver users are then free to choose which implementation that is available to them.
+pub struct BlockingAsync<T> {
+    wrapped: T,
+}
+
+impl<T> BlockingAsync<T> {
+    /// Create a new instance of a wrapper for a given peripheral.
+    pub fn new(wrapped: T) -> Self {
+        Self { wrapped }
+    }
+}
+
+//
+// I2C implementatinos
+//
+
+impl<T, E> crate::i2c::I2c for BlockingAsync<T>
+where
+    E: 'static,
+    T: blocking::i2c::WriteRead<Error = E>
+        + blocking::i2c::Read<Error = E>
+        + blocking::i2c::Write<Error = E>,
+{
+    type Error = E;
+
+    #[rustfmt::skip]
+    type WriteFuture<'a> where Self: 'a = impl Future<Output = Result<(), Self::Error>> + 'a;
+    #[rustfmt::skip]
+    type ReadFuture<'a> where Self: 'a = impl Future<Output = Result<(), Self::Error>> + 'a;
+    #[rustfmt::skip]
+    type WriteReadFuture<'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> {
+        async move { self.wrapped.read(address, buffer) }
+    }
+
+    fn write<'a>(&'a mut self, address: u8, bytes: &'a [u8]) -> Self::WriteFuture<'a> {
+        async move { self.wrapped.write(address, bytes) }
+    }
+
+    fn write_read<'a>(
+        &'a mut self,
+        address: u8,
+        bytes: &'a [u8],
+        buffer: &'a mut [u8],
+    ) -> Self::WriteReadFuture<'a> {
+        async move { self.wrapped.write_read(address, bytes, buffer) }
+    }
+}
+
+//
+// SPI implementatinos
+//
+
+impl<T, E, Word> crate::spi::Spi<Word> for BlockingAsync<T>
+where
+    T: blocking::spi::Write<Word, Error = E>,
+{
+    type Error = E;
+}
+
+impl<T, E, Word> crate::spi::FullDuplex<Word> for BlockingAsync<T>
+where
+    E: 'static,
+    Word: Clone,
+    T: blocking::spi::Transfer<Word, Error = E> + blocking::spi::Write<Word, Error = E>,
+{
+    #[rustfmt::skip]
+    type WriteReadFuture<'a> where Word: 'a, Self: 'a = impl Future<Output = Result<(), Self::Error>> + 'a;
+
+    fn read_write<'a>(
+        &'a mut self,
+        read: &'a mut [Word],
+        write: &'a [Word],
+    ) -> Self::WriteReadFuture<'a> {
+        async move {
+            // Ensure we write the expected bytes
+            for i in 0..core::cmp::min(read.len(), write.len()) {
+                read[i] = write[i].clone();
+            }
+            self.wrapped.transfer(read)?;
+            Ok(())
+        }
+    }
+}
+
+impl<T, E, Word> crate::spi::Write<Word> for BlockingAsync<T>
+where
+    E: 'static,
+    Word: Clone,
+    T: blocking::spi::Write<Word, Error = E>,
+{
+    #[rustfmt::skip]
+    type WriteFuture<'a> where Word: 'a, Self: 'a = impl Future<Output = Result<(), Self::Error>> + 'a;
+
+    fn write<'a>(&'a mut self, data: &'a [Word]) -> Self::WriteFuture<'a> {
+        async move { self.wrapped.write(data) }
+    }
+}
+
+impl<T, E, Word> crate::spi::Read<Word> for BlockingAsync<T>
+where
+    E: 'static,
+    Word: Clone,
+    T: blocking::spi::Transfer<Word, Error = E> + blocking::spi::Write<Word, Error = E>,
+{
+    #[rustfmt::skip]
+    type ReadFuture<'a> where Word: 'a, Self: 'a = impl Future<Output = Result<(), Self::Error>> + 'a;
+
+    fn read<'a>(&'a mut self, data: &'a mut [Word]) -> Self::ReadFuture<'a> {
+        async move {
+            self.wrapped.transfer(data)?;
+            Ok(())
+        }
+    }
+}
+
+// Uart implementatinos
+impl<T> crate::uart::Read for BlockingAsync<T>
+where
+    T: serial::Read<u8>,
+{
+    #[rustfmt::skip]
+    type ReadFuture<'a> where T: 'a = impl Future<Output = Result<(), crate::uart::Error>> + 'a;
+    fn read<'a>(&'a mut self, buf: &'a mut [u8]) -> Self::ReadFuture<'a> {
+        async move {
+            let mut pos = 0;
+            while pos < buf.len() {
+                match self.wrapped.read() {
+                    Err(nb::Error::WouldBlock) => {}
+                    Err(_) => return Err(crate::uart::Error::Other),
+                    Ok(b) => {
+                        buf[pos] = b;
+                        pos += 1;
+                    }
+                }
+            }
+            Ok(())
+        }
+    }
+}
+
+impl<T> crate::uart::Write for BlockingAsync<T>
+where
+    T: blocking::serial::Write<u8>,
+{
+    #[rustfmt::skip]
+    type WriteFuture<'a> where T: 'a = impl Future<Output = Result<(), crate::uart::Error>> + 'a;
+    fn write<'a>(&'a mut self, buf: &'a [u8]) -> Self::WriteFuture<'a> {
+        async move {
+            self.wrapped
+                .bwrite_all(buf)
+                .map_err(|_| crate::uart::Error::Other)?;
+            self.wrapped.bflush().map_err(|_| crate::uart::Error::Other)
+        }
+    }
+}
diff --git a/embassy-traits/src/lib.rs b/embassy-traits/src/lib.rs
index 65fb95bd4..a5342b77e 100644
--- a/embassy-traits/src/lib.rs
+++ b/embassy-traits/src/lib.rs
@@ -2,6 +2,7 @@
 #![feature(generic_associated_types)]
 #![feature(type_alias_impl_trait)]
 
+pub mod adapter;
 pub mod delay;
 pub mod flash;
 pub mod gpio;