[alsa-devel] [PATCH - IOPLUG DRAIN 1/1] jack: Support snd_pcm_drain()

[twischer at de.adit-jv.com]

From: Timo Wischer <twischer at de.adit-jv.com>

Without this commit the JACK thread will be stopped
before the ALSA buffer was completely forwarded to
the JACK daemon.

Signed-off-by: Timo Wischer <twischer at de.adit-jv.com>

diff --git a/jack/pcm_jack.c b/jack/pcm_jack.c
index e3df4d2..5c4d0fc 100644
--- a/jack/pcm_jack.c
+++ b/jack/pcm_jack.c
@@ -85,7 +85,12 @@ static int pcm_poll_unblock_check(snd_pcm_ioplug_t *io)
 	snd_pcm_jack_t *jack = io->private_data;
 
 	avail = snd_pcm_avail_update(io->pcm);
-	if (avail < 0 || avail >= jack->min_avail) {
+	/* In draining state poll_fd is used to wait till all pending frames are
+	 * played. Therefore it has to be guarantee that a poll event is also
+	 * generated if the buffer contains less than min_avail frames.
+	 */
+	if (avail < 0 || avail >= jack->min_avail ||
+	    io->state == SND_PCM_STATE_DRAINING) {
 		write(jack->fd, &buf, 1);
 		return 1;
 	}
@@ -161,7 +166,8 @@ snd_pcm_jack_process_cb(jack_nframes_t nframes, snd_pcm_ioplug_t *io)
 		jack->areas[channel].step = jack->sample_bits;
 	}
 
-	if (io->state == SND_PCM_STATE_RUNNING) {
+	if (io->state == SND_PCM_STATE_RUNNING ||
+	    io->state == SND_PCM_STATE_DRAINING) {
 		snd_pcm_uframes_t hw_ptr = jack->hw_ptr;
 		const snd_pcm_uframes_t hw_avail = snd_pcm_ioplug_hw_avail(io, hw_ptr,
 									   io->appl_ptr);
@@ -307,6 +313,29 @@ static int snd_pcm_jack_start(snd_pcm_ioplug_t *io)
 	return 0;
 }
 
+static int snd_pcm_jack_drain(snd_pcm_ioplug_t *io)
+{
+	snd_pcm_jack_t *jack = io->private_data;
+
+	/* Immediately stop on capture device.
+	 * snd_pcm_jack_stop() will be automatically called
+	 * by snd_pcm_ioplug_drain()
+	 */
+	if (io->stream == SND_PCM_STREAM_CAPTURE)
+		return 0;
+
+	if (snd_pcm_ioplug_hw_avail(io, jack->hw_ptr, io->appl_ptr) <= 0) {
+		/* No data pending. Nothing to drain. */
+		return 0;
+	}
+
+	/* start device if not yet done */
+	if (!jack->activated)
+		snd_pcm_jack_start(io);
+
+	return -EAGAIN;
+}
+
 static int snd_pcm_jack_stop(snd_pcm_ioplug_t *io)
 {
 	snd_pcm_jack_t *jack = io->private_data;
@@ -333,6 +362,7 @@ static snd_pcm_ioplug_callback_t jack_pcm_callback = {
 	.stop = snd_pcm_jack_stop,
 	.pointer = snd_pcm_jack_pointer,
 	.prepare = snd_pcm_jack_prepare,
+	.drain = snd_pcm_jack_drain,
 	.poll_revents = snd_pcm_jack_poll_revents,
 };
 
-- 
2.7.4