feat(uart8250): implement embedded_hal serial traits

Author: qwandor

Cargo.lock

@@ -15,11 +15,11 @@ readme = "README.md"
 
 [dependencies]
 bitflags = "1"
-# embedded-hal = { version = "=1.0.0-alpha.4", optional = true }
-# nb = { version = "1", optional = true }
+embedded-hal = { version = "0.2.7", optional = true }
+nb = { version = "1.0.0", optional = true }
 volatile-register = "0.2"
 
 [features]
 default = []
-# embedded = ["embedded-hal", "nb"]
+embedded = ["embedded-hal", "nb"]
 fmt = []

uart8250/Cargo.toml

@@ -1,4 +1,6 @@
 use bitflags::bitflags;
+#[cfg(feature = "embedded")]
+use core::convert::Infallible;
 use core::fmt::{self, Display, Formatter};
 
 use crate::registers::Registers;
@@ -678,6 +680,34 @@ impl<'a> fmt::Write for MmioUart8250<'a> {
     }
 }
 
+#[cfg(feature = "embedded")]
+impl embedded_hal::serial::Read<u8> for MmioUart8250<'_> {
+    type Error = Infallible;
+
+    fn read(&mut self) -> nb::Result<u8, Self::Error> {
+        self.read_byte().ok_or(nb::Error::WouldBlock)
+    }
+}
+
+#[cfg(feature = "embedded")]
+impl embedded_hal::serial::Write<u8> for MmioUart8250<'_> {
+    type Error = Infallible;
+
+    fn write(&mut self, byte: u8) -> nb::Result<(), Self::Error> {
+        self.write_byte(byte).map_err(|e| match e {
+            TransmitError::BufferFull => nb::Error::WouldBlock,
+        })
+    }
+
+    fn flush(&mut self) -> nb::Result<(), Self::Error> {
+        if self.is_data_holding_registers_empty() {
+            Ok(())
+        } else {
+            Err(nb::Error::WouldBlock)
+        }
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;