DMA: add a method to wait for transfer completion

Author: imihajlow

CHANGELOG.md

@@ -43,6 +43,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - example of using USB CDC with interrupts.
 - Added non-blocking I2C based on DMA [#534]
 - Added Transactional I2C API [#542]
+- Added wait method for DMA Transfer.
 
 [#481]: https://github.com/stm32-rs/stm32f4xx-hal/pull/481
 [#489]: https://github.com/stm32-rs/stm32f4xx-hal/pull/489

src/dma/mod.rs

@@ -1355,6 +1355,12 @@ where
         &mut self.stream
     }
 
+    /// Wait for the transfer to complete.
+    #[inline(always)]
+    pub fn wait(&self) {
+        while !STREAM::get_transfer_complete_flag() {}
+    }
+
     /// Applies all fields in DmaConfig.
     fn apply_config(stream: &mut STREAM, config: config::DmaConfig) {
         let msize = mem::size_of::<<PERIPHERAL as PeriAddress>::MemSize>() / 2;