Add an is_done() poll method to DMA transfers

Implement it by forwarding to the DMA channel's existing is_done mehod.
Add the implementation to both SPI and I2S DMA transfer structs.

esp-hal-common/src/dma/mod.rs

@@ -846,13 +846,17 @@ where
 pub trait DmaTransfer<B, T>: Drop {
     /// Wait for the transfer to finish.
     fn wait(self) -> (B, T);
+    /// Check if the transfer is finished.
+    fn is_done(&self) -> bool;
 }
 
 /// Trait to be implemented for an in progress dma transfer.
 #[allow(drop_bounds)]
 pub trait DmaTransferRxTx<BR, BT, T>: Drop {
     /// Wait for the transfer to finish.
     fn wait(self) -> (BR, BT, T);
+    /// Check if the transfer is finished.
+    fn is_done(&self) -> bool;
 }
 
 #[cfg(feature = "async")]

esp-hal-common/src/i2s.rs

@@ -326,6 +326,11 @@ where
             (buffer, payload)
         }
     }
+
+    /// Check if the DMA transfer is complete
+    fn is_done(&self) -> bool {
+        self.i2s_tx.tx_channel.is_done()
+    }
 }
 
 impl<'d, T, P, TX, BUFFER> Drop for I2sWriteDmaTransfer<T, P, TX, BUFFER>
@@ -451,6 +456,11 @@ where
             (buffer, payload)
         }
     }
+
+    /// Check if the DMA transfer is complete
+    fn is_done(&self) -> bool {
+        self.i2s_rx.rx_channel.is_done()
+    }
 }
 
 impl<T, P, RX, BUFFER> Drop for I2sReadDmaTransfer<T, P, RX, BUFFER>

esp-hal-common/src/spi.rs

@@ -861,6 +861,12 @@ pub mod dma {
                 (rbuffer, tbuffer, payload)
             }
         }
+
+        /// Check if the DMA transfer is complete
+        fn is_done(&self) -> bool {
+            let ch = &self.spi_dma.channel;
+            ch.tx.is_done() && ch.rx.is_done()
+        }
     }
 
     impl<'d, T, TX, RX, P, RXBUF, TXBUF, M> Drop
@@ -918,6 +924,12 @@ pub mod dma {
                 (buffer, payload)
             }
         }
+
+        /// Check if the DMA transfer is complete
+        fn is_done(&self) -> bool {
+            let ch = &self.spi_dma.channel;
+            ch.tx.is_done() && ch.rx.is_done()
+        }
     }
 
     impl<'d, T, TX, RX, P, BUFFER, M> Drop for SpiDmaTransfer<'d, T, TX, RX, P, BUFFER, M>