[alsa-devel] [PATCH 3/4] ALSA: compress: Don't allow drain operations on capture streams

[Charles Keepax]

Partial drain and next track are intended for gapless playback and
don't really have an obvious interpretation for a capture stream, so
makes sense to not allow those operations on capture streams. Drain
would make sense on a capture stream but currently the implementation
of drain involves the kernel waiting for the DSP to consume its
available data, whereas a capture drain would involve waiting for
user-space to consume the data available on the DSP. Disallow drain
on capture streams until that is implemented.

Signed-off-by: Charles Keepax <ckeepax at opensource.cirrus.com>
---
 sound/core/compress_offload.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/sound/core/compress_offload.c b/sound/core/compress_offload.c
index e1a216fd832f9..c7d56cee0d510 100644
--- a/sound/core/compress_offload.c
+++ b/sound/core/compress_offload.c
@@ -829,6 +829,10 @@ static int snd_compr_drain(struct snd_compr_stream *stream)
 		break;
 	}
 
+	/* drain not implemented for capture streams yet */
+	if (stream->direction == SND_COMPRESS_CAPTURE)
+		return -EPERM;
+
 	retval = stream->ops->trigger(stream, SND_COMPR_TRIGGER_DRAIN);
 	if (retval) {
 		pr_debug("SND_COMPR_TRIGGER_DRAIN failed %d\n", retval);
@@ -847,6 +851,10 @@ static int snd_compr_next_track(struct snd_compr_stream *stream)
 	if (stream->runtime->state != SNDRV_PCM_STATE_RUNNING)
 		return -EPERM;
 
+	/* next track doesn't have any meaning for capture streams */
+	if (stream->direction == SND_COMPRESS_CAPTURE)
+		return -EPERM;
+
 	/* you can signal next track if this is intended to be a gapless stream
 	 * and current track metadata is set
 	 */
@@ -874,6 +882,10 @@ static int snd_compr_partial_drain(struct snd_compr_stream *stream)
 		break;
 	}
 
+	/* partial drain doesn't have any meaning for capture streams */
+	if (stream->direction == SND_COMPRESS_CAPTURE)
+		return -EPERM;
+
 	/* stream can be drained only when next track has been signalled */
 	if (stream->next_track == false)
 		return -EPERM;
-- 
2.11.0