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Merge pull request #1681 from alexferro/feature/stm32-dma-read-exact

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Add a STM32/DMARingBuffer::read_exact helper
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xoviat 2023-07-28 01:16:48 +00:00 committed by GitHub
commit 44c8db2911
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3 changed files with 91 additions and 15 deletions
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44
embassy-stm32/src/dma/bdma.rs
View file

@ -466,15 +466,53 @@ impl<'a, C: Channel, W: Word> RingBuffer<'a, C, W> {
self.ringbuf.clear(DmaCtrlImpl(self.channel.reborrow()));
}
/// Read bytes from the ring buffer
/// Read elements from the ring buffer
/// Return a tuple of the length read and the length remaining in the buffer
/// If not all of the bytes were read, then there will be some bytes in the buffer remaining
/// The length remaining is the capacity, ring_buf.len(), less the bytes remaining after the read
/// If not all of the elements were read, then there will be some elements in the buffer remaining
/// The length remaining is the capacity, ring_buf.len(), less the elements remaining after the read
/// OverrunError is returned if the portion to be read was overwritten by the DMA controller.
pub fn read(&mut self, buf: &mut [W]) -> Result<(usize, usize), OverrunError> {
self.ringbuf.read(DmaCtrlImpl(self.channel.reborrow()), buf)
}
/// Read an exact number of elements from the ringbuffer.
///
/// Returns the remaining number of elements available for immediate reading.
/// OverrunError is returned if the portion to be read was overwritten by the DMA controller.
///
/// Async/Wake Behavior:
/// The underlying DMA peripheral only can wake us when its buffer pointer has reached the halfway point,
/// and when it wraps around. This means that when called with a buffer of length 'M', when this
/// ring buffer was created with a buffer of size 'N':
/// - If M equals N/2 or N/2 divides evenly into M, this function will return every N/2 elements read on the DMA source.
/// - Otherwise, this function may need up to N/2 extra elements to arrive before returning.
pub async fn read_exact(&mut self, buffer: &mut [W]) -> Result<usize, OverrunError> {
use core::future::poll_fn;
use core::sync::atomic::compiler_fence;
let mut read_data = 0;
let buffer_len = buffer.len();
poll_fn(|cx| {
self.set_waker(cx.waker());
compiler_fence(Ordering::SeqCst);
match self.read(&mut buffer[read_data..buffer_len]) {
Ok((len, remaining)) => {
read_data += len;
if read_data == buffer_len {
Poll::Ready(Ok(remaining))
} else {
Poll::Pending
}
}
Err(e) => Poll::Ready(Err(e)),
}
})
.await
}
/// The capacity of the ringbuffer
pub fn cap(&self) -> usize {
self.ringbuf.cap()

44
embassy-stm32/src/dma/dma.rs
View file

@ -711,15 +711,53 @@ impl<'a, C: Channel, W: Word> RingBuffer<'a, C, W> {
self.ringbuf.clear(DmaCtrlImpl(self.channel.reborrow()));
}
/// Read bytes from the ring buffer
/// Read elements from the ring buffer
/// Return a tuple of the length read and the length remaining in the buffer
/// If not all of the bytes were read, then there will be some bytes in the buffer remaining
/// The length remaining is the capacity, ring_buf.len(), less the bytes remaining after the read
/// If not all of the elements were read, then there will be some elements in the buffer remaining
/// The length remaining is the capacity, ring_buf.len(), less the elements remaining after the read
/// OverrunError is returned if the portion to be read was overwritten by the DMA controller.
pub fn read(&mut self, buf: &mut [W]) -> Result<(usize, usize), OverrunError> {
self.ringbuf.read(DmaCtrlImpl(self.channel.reborrow()), buf)
}
/// Read an exact number of elements from the ringbuffer.
///
/// Returns the remaining number of elements available for immediate reading.
/// OverrunError is returned if the portion to be read was overwritten by the DMA controller.
///
/// Async/Wake Behavior:
/// The underlying DMA peripheral only can wake us when its buffer pointer has reached the halfway point,
/// and when it wraps around. This means that when called with a buffer of length 'M', when this
/// ring buffer was created with a buffer of size 'N':
/// - If M equals N/2 or N/2 divides evenly into M, this function will return every N/2 elements read on the DMA source.
/// - Otherwise, this function may need up to N/2 extra elements to arrive before returning.
pub async fn read_exact(&mut self, buffer: &mut [W]) -> Result<usize, OverrunError> {
use core::future::poll_fn;
use core::sync::atomic::compiler_fence;
let mut read_data = 0;
let buffer_len = buffer.len();
poll_fn(|cx| {
self.set_waker(cx.waker());
compiler_fence(Ordering::SeqCst);
match self.read(&mut buffer[read_data..buffer_len]) {
Ok((len, remaining)) => {
read_data += len;
if read_data == buffer_len {
Poll::Ready(Ok(remaining))
} else {
Poll::Pending
}
}
Err(e) => Poll::Ready(Err(e)),
}
})
.await
}
// The capacity of the ringbuffer
pub fn cap(&self) -> usize {
self.ringbuf.cap()

18
embassy-stm32/src/dma/ringbuffer.rs
View file

@ -72,10 +72,10 @@ impl<'a, W: Word> DmaRingBuffer<'a, W> {
self.cap() - remaining_transfers
}
/// Read bytes from the ring buffer
/// Read elements from the ring buffer
/// Return a tuple of the length read and the length remaining in the buffer
/// If not all of the bytes were read, then there will be some bytes in the buffer remaining
/// The length remaining is the capacity, ring_buf.len(), less the bytes remaining after the read
/// If not all of the elements were read, then there will be some elements in the buffer remaining
/// The length remaining is the capacity, ring_buf.len(), less the elements remaining after the read
/// OverrunError is returned if the portion to be read was overwritten by the DMA controller.
pub fn read(&mut self, mut dma: impl DmaCtrl, buf: &mut [W]) -> Result<(usize, usize), OverrunError> {
/*
@ -95,11 +95,11 @@ impl<'a, W: Word> DmaRingBuffer<'a, W> {
*/
let end = self.pos(dma.get_remaining_transfers());
if self.start == end && dma.get_complete_count() == 0 {
// No bytes are available in the buffer
// No elements are available in the buffer
Ok((0, self.cap()))
} else if self.start < end {
// The available, unread portion in the ring buffer DOES NOT wrap
// Copy out the bytes from the dma buffer
// Copy out the elements from the dma buffer
let len = self.copy_to(buf, self.start..end);
compiler_fence(Ordering::SeqCst);
@ -128,7 +128,7 @@ impl<'a, W: Word> DmaRingBuffer<'a, W> {
// The DMA writer has wrapped since we last read and is currently
// writing (or the next byte added will be) in the beginning of the ring buffer.
// The provided read buffer is not large enough to include all bytes from the tail of the dma buffer.
// The provided read buffer is not large enough to include all elements from the tail of the dma buffer.
// Copy out from the dma buffer
let len = self.copy_to(buf, self.start..self.cap());
@ -154,8 +154,8 @@ impl<'a, W: Word> DmaRingBuffer<'a, W> {
// The DMA writer has wrapped since we last read and is currently
// writing (or the next byte added will be) in the beginning of the ring buffer.
// The provided read buffer is large enough to include all bytes from the tail of the dma buffer,
// so the next read will not have any unread tail bytes in the ring buffer.
// The provided read buffer is large enough to include all elements from the tail of the dma buffer,
// so the next read will not have any unread tail elements in the ring buffer.
// Copy out from the dma buffer
let tail = self.copy_to(buf, self.start..self.cap());
@ -180,7 +180,7 @@ impl<'a, W: Word> DmaRingBuffer<'a, W> {
}
/// Copy from the dma buffer at `data_range` into `buf`
fn copy_to(&mut self, buf: &mut [W], data_range: Range<usize>) -> usize {
// Limit the number of bytes that can be copied
// Limit the number of elements that can be copied
let length = usize::min(data_range.len(), buf.len());
// Copy from dma buffer into read buffer