Merge pull request #3451 from dvdsk/read_ready

stm32/uart impl ReadReady for RingbufferdUart

embassy-stm32/src/dma/ringbuffer/mod.rs

@@ -21,6 +21,10 @@ pub trait DmaCtrl {
 #[cfg_attr(feature = "defmt", derive(defmt::Format))]
 pub enum Error {
     Overrun,
+    /// the newly read DMA positions don't make sense compared to the previous
+    /// ones. This can usually only occur due to wrong Driver implementation, if
+    /// the driver author (or the user using raw metapac code) directly resets
+    /// the channel for instance.
     DmaUnsynced,
 }
 

embassy-stm32/src/usart/ringbuffered.rs

@@ -5,6 +5,7 @@ use core::task::Poll;
 
 use embassy_embedded_hal::SetConfig;
 use embassy_hal_internal::PeripheralRef;
+use embedded_io_async::ReadReady;
 use futures_util::future::{select, Either};
 
 use super::{clear_interrupt_flags, rdr, reconfigure, sr, Config, ConfigError, Error, Info, State, UartRx};
@@ -262,3 +263,20 @@ impl embedded_io_async::Read for RingBufferedUartRx<'_> {
         self.read(buf).await
     }
 }
+
+impl ReadReady for RingBufferedUartRx<'_> {
+    fn read_ready(&mut self) -> Result<bool, Self::Error> {
+        let len = self.ring_buf.len().map_err(|e| match e {
+            crate::dma::ringbuffer::Error::Overrun => Self::Error::Overrun,
+            crate::dma::ringbuffer::Error::DmaUnsynced => {
+                error!(
+                    "Ringbuffer error: DmaUNsynced, driver implementation is 
+                    probably bugged please open an issue"
+                );
+                // we report this as overrun since its recoverable in the same way
+                Self::Error::Overrun
+            }
+        })?;
+        Ok(len > 0)
+    }
+}