do not use avail_min for ALSA drain

removes the possibility of a drain being affected by an application
changing avail_min.

src/asound/bluealsa-pcm.c

@@ -694,11 +694,6 @@ static int bluealsa_drain(snd_pcm_ioplug_t *io) {
 
 	bool aborted = false;
 
-	/* Temporarily set avail_min such that the IO thread does not wake us
-	 * until the buffer is empty. */
-	snd_pcm_uframes_t saved_avail_min = pcm->io_avail_min;
-	pcm->io_avail_min = io->buffer_size;
-
 	struct pollfd pfd = { pcm->event_fd, POLLIN, 0 };
 	snd_pcm_sframes_t hw_ptr;
 	int ret = 0;
@@ -757,9 +752,6 @@ static int bluealsa_drain(snd_pcm_ioplug_t *io) {
 
 	}
 
-	/* Restore the avail_min parameter */
-	pcm->io_avail_min = saved_avail_min;
-
 	if (io->state == SND_PCM_STATE_DRAINING && !aborted)
 		if (!bluealsa_dbus_pcm_ctrl_send_drain(pcm->ba_pcm_ctrl_fd, NULL)) {
 			bluealsa_stop(io);
@@ -1039,6 +1031,15 @@ static int bluealsa_poll_revents(snd_pcm_ioplug_t *io, struct pollfd *pfd,
 					*revents = 0;
 				}
 				break;
+			case SND_PCM_STATE_DRAINING:
+				/* BlueALSA does not drain capture PCMs. So this state only
+				 * occurs with playback PCMs. Do not wake the application until
+				 * the buffer is empty. */
+				if ((snd_pcm_uframes_t)avail < io->buffer_size) {
+					ready = false;
+					*revents = 0;
+				}
+				break;
 			case SND_PCM_STATE_XRUN:
 			case SND_PCM_STATE_PAUSED:
 			case SND_PCM_STATE_SUSPENDED: