pcm: ioplug: Transfer all available data

The snd_pcm_mmap_begin() call returns the amount of contiguous data,
which is less than the total available if it wraps around the buffer
boundary.

If we don't handle this split we leave stale data in the buffer that
should have been overwritten, as well as unread data in the io_plugin
that gets transferred on a subsequent call at the wrong offset.

Signed-off-by: Rob Duncan <rduncan@teslamotors.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

src/pcm/pcm_ioplug.c

@@ -716,6 +716,8 @@ static snd_pcm_sframes_t snd_pcm_ioplug_avail_update(snd_pcm_t *pcm)
 	snd_pcm_ioplug_hw_ptr_update(pcm);
 	if (io->data->state == SND_PCM_STATE_XRUN)
 		return -EPIPE;
+
+	avail = snd_pcm_mmap_avail(pcm);
 	if (pcm->stream == SND_PCM_STREAM_CAPTURE &&
 	    pcm->access != SND_PCM_ACCESS_RW_INTERLEAVED &&
 	    pcm->access != SND_PCM_ACCESS_RW_NONINTERLEAVED) {
@@ -728,9 +730,19 @@ static snd_pcm_sframes_t snd_pcm_ioplug_avail_update(snd_pcm_t *pcm)
 			result = io->data->callback->transfer(io->data, areas, offset, size);
 			if (result < 0)
 				return result;
+
+			/* If the available data doesn't fit in the
+			   contiguous area at the end of the mmap we
+			   must transfer the remaining data to the
+			   beginning of the mmap. */
+			if (size < avail) {
+				result = io->data->callback->transfer(io->data, areas,
+								      0, avail - size);
+				if (result < 0)
+					return result;
+			}
 		}
 	}
-	avail = snd_pcm_mmap_avail(pcm);
 	if (avail > io->avail_max)
 		io->avail_max = avail;
 	return (snd_pcm_sframes_t)avail;