pcm: improve handling for snd_pcm_wait()

The snd_pcm_wait() function is called also internally from
the various plugins to wait for the drain with -1 and from i/o
routines in pcm.c.

Define two special negative timeout values to distinguish the
drain and i/o wait and calculate the maximal timeout according
the wait place.

Fixes: https://github.com/alsa-project/alsa-lib/issues/228
Signed-off-by: Jaroslav Kysela <perex@perex.cz>

9 files changed, 55 insertions, 10 deletions

diff --git a/include/pcm.h b/include/pcm.h
index 966d6ffd..25cd12d1 100644
--- a/include/pcm.h
+++ b/include/pcm.h
@@ -498,6 +498,13 @@ typedef union _snd_pcm_sync_id {
 	unsigned int id32[4];
 } snd_pcm_sync_id_t;
 
+/** Infinite wait for snd_pcm_wait() */
+#define SND_PCM_WAIT_INFINITE		(-1)
+/** Wait for next i/o in snd_pcm_wait() */
+#define SND_PCM_WAIT_IO			(-10001)
+/** Wait for drain in snd_pcm_wait() */
+#define SND_PCM_WAIT_DRAIN		(-10002)
+
 /** #SND_PCM_TYPE_METER scope handle */
 typedef struct _snd_pcm_scope snd_pcm_scope_t;
 
diff --git a/src/pcm/pcm.c b/src/pcm/pcm.c
index 997a8a6a..01c624d3 100644
--- a/src/pcm/pcm.c
+++ b/src/pcm/pcm.c
@@ -2834,7 +2834,8 @@ int snd_pcm_open_named_slave(snd_pcm_t **pcmp, const char *name,
  * \brief Wait for a PCM to become ready
  * \param pcm PCM handle
  * \param timeout maximum time in milliseconds to wait,
- *        a negative value means infinity
+ *        a -1 value means infinity (SND_PCM_WAIT_INFINITE),
+ *	       see also SND_PCM_WAIT_IO and SND_PCM_WAIT_DRAIN
  * \return a positive value on success otherwise a negative error code
  *         (-EPIPE for the xrun and -ESTRPIPE for the suspended status,
  *          others for general errors) 
@@ -2869,6 +2870,37 @@ int __snd_pcm_wait_in_lock(snd_pcm_t *pcm, int timeout)
 	return snd_pcm_wait_nocheck(pcm, timeout);
 }
 
+static int __snd_pcm_wait_io_timeout(snd_pcm_t *pcm)
+{
+	int timeout;
+
+	/* period size is the time boundary */
+	timeout = (pcm->period_size * 1000ULL) / pcm->rate;
+	/* should not happen */
+	if (timeout < 0)
+		timeout = 0;
+	/* add extra time of 200 milliseconds */
+	timeout += 200;
+	return timeout;
+}
+
+static int __snd_pcm_wait_drain_timeout(snd_pcm_t *pcm)
+{
+	int timeout;
+
+	/* for capture, there's no reason to wait, just one iteration */
+	if (snd_pcm_stream(pcm) == SND_PCM_STREAM_CAPTURE)
+		return 0;
+	/* result is in milliseconds */
+	timeout = (snd_pcm_mmap_playback_delay(pcm) * 1000LL) / pcm->rate;
+	/* should not happen */
+	if (timeout < 0)
+		timeout = 0;
+	/* add extra time of 200 milliseconds */
+	timeout += 200;
+	return timeout;
+}
+
 /* 
  * like snd_pcm_wait() but doesn't check mmap_avail before calling poll()
  *
@@ -2895,6 +2927,12 @@ int snd_pcm_wait_nocheck(snd_pcm_t *pcm, int timeout)
 		SNDMSG("invalid poll descriptors %d\n", err);
 		return -EIO;
 	}
+	if (timeout == SND_PCM_WAIT_IO)
+		timeout = __snd_pcm_wait_io_timeout(pcm);
+	else if (timeout == SND_PCM_WAIT_DRAIN)
+		timeout = __snd_pcm_wait_drain_timeout(pcm);
+	else if (timeout < -1)
+		SNDMSG("invalid snd_pcm_wait timeout argument %d\n", timeout);
 	do {
 		__snd_pcm_unlock(pcm->fast_op_arg);
 		err_poll = poll(pfd, npfds, timeout);
@@ -7525,7 +7563,7 @@ snd_pcm_sframes_t snd_pcm_read_areas(snd_pcm_t *pcm, const snd_pcm_channel_area_
 				goto _end;
 			}
 
-			err = __snd_pcm_wait_in_lock(pcm, -1);
+			err = __snd_pcm_wait_in_lock(pcm, SND_PCM_WAIT_IO);
 			if (err < 0)
 				break;
 			goto _again;
@@ -7594,7 +7632,7 @@ snd_pcm_sframes_t snd_pcm_write_areas(snd_pcm_t *pcm, const snd_pcm_channel_area
 					goto _end;
 				}
 
-				err = snd_pcm_wait_nocheck(pcm, -1);
+				err = snd_pcm_wait_nocheck(pcm, SND_PCM_WAIT_IO);
 				if (err < 0)
 					break;
 				goto _again;
diff --git a/src/pcm/pcm_dmix.c b/src/pcm/pcm_dmix.c
index b93c955c..b0d0a43e 100644
--- a/src/pcm/pcm_dmix.c
+++ b/src/pcm/pcm_dmix.c
@@ -623,7 +623,7 @@ static int __snd_pcm_dmix_drain(snd_pcm_t *pcm)
 		if (dmix->state == SND_PCM_STATE_DRAINING) {
 			snd_pcm_dmix_sync_area(pcm);
 			if ((pcm->mode & SND_PCM_NONBLOCK) == 0) {
-				snd_pcm_wait_nocheck(pcm, -1);
+				snd_pcm_wait_nocheck(pcm, SND_PCM_WAIT_DRAIN);
 				snd_pcm_direct_clear_timer_queue(dmix); /* force poll to wait */
 			}
 
diff --git a/src/pcm/pcm_dshare.c b/src/pcm/pcm_dshare.c
index d7be8fbb..454b39a9 100644
--- a/src/pcm/pcm_dshare.c
+++ b/src/pcm/pcm_dshare.c
@@ -400,7 +400,7 @@ static int __snd_pcm_dshare_drain(snd_pcm_t *pcm)
 		}
 		if (dshare->state == SND_PCM_STATE_DRAINING) {
 			snd_pcm_dshare_sync_area(pcm);
-			snd_pcm_wait_nocheck(pcm, -1);
+			snd_pcm_wait_nocheck(pcm, SND_PCM_WAIT_DRAIN);
 			snd_pcm_direct_clear_timer_queue(dshare); /* force poll to wait */
 
 			switch (snd_pcm_state(dshare->spcm)) {
diff --git a/src/pcm/pcm_dsnoop.c b/src/pcm/pcm_dsnoop.c
index cb2eee32..d3ce300c 100644
--- a/src/pcm/pcm_dsnoop.c
+++ b/src/pcm/pcm_dsnoop.c
@@ -301,7 +301,7 @@ static int __snd_pcm_dsnoop_drain(snd_pcm_t *pcm)
 			break;
 		if (pcm->mode & SND_PCM_NONBLOCK)
 			return -EAGAIN;
-		__snd_pcm_wait_in_lock(pcm, -1);
+		__snd_pcm_wait_in_lock(pcm, SND_PCM_WAIT_DRAIN);
 	}
 	pcm->stop_threshold = stop_threshold;
 	return snd_pcm_dsnoop_drop(pcm);
diff --git a/src/pcm/pcm_ioplug.c b/src/pcm/pcm_ioplug.c
index 98184398..09454a29 100644
--- a/src/pcm/pcm_ioplug.c
+++ b/src/pcm/pcm_ioplug.c
@@ -522,7 +522,7 @@ static int ioplug_drain_via_poll(snd_pcm_t *pcm)
 		/* in non-blocking mode, let application to poll() by itself */
 		if (io->data->nonblock)
 			return -EAGAIN;
-		if (snd_pcm_wait_nocheck(pcm, -1) < 0)
+		if (snd_pcm_wait_nocheck(pcm, SND_PCM_WAIT_DRAIN) < 0)
 			break;
 	}
 
diff --git a/src/pcm/pcm_rate.c b/src/pcm/pcm_rate.c
index c8076859..44d7e760 100644
--- a/src/pcm/pcm_rate.c
+++ b/src/pcm/pcm_rate.c
@@ -1146,7 +1146,7 @@ static int snd_pcm_rate_drain(snd_pcm_t *pcm)
 			snd_pcm_uframes_t psize, spsize;
 			int err;
 
-			err = __snd_pcm_wait_in_lock(rate->gen.slave, -1);
+			err = __snd_pcm_wait_in_lock(rate->gen.slave, SND_PCM_WAIT_DRAIN);
 			if (err < 0)
 				break;
 			if (size > pcm->period_size) {
diff --git a/src/pcm/pcm_share.c b/src/pcm/pcm_share.c
index ac088472..677f4132 100644
--- a/src/pcm/pcm_share.c
+++ b/src/pcm/pcm_share.c
@@ -1194,7 +1194,7 @@ static int snd_pcm_share_drain(snd_pcm_t *pcm)
 			_snd_pcm_share_update(pcm);
 			Pthread_mutex_unlock(&slave->mutex);
 			if (!(pcm->mode & SND_PCM_NONBLOCK))
-				snd_pcm_wait(pcm, -1);
+				snd_pcm_wait(pcm, SND_PCM_WAIT_DRAIN);
 			return 0;
 		default:
 			assert(0);
diff --git a/src/pcm/pcm_shm.c b/src/pcm/pcm_shm.c
index 12828958..f0bfd934 100644
--- a/src/pcm/pcm_shm.c
+++ b/src/pcm/pcm_shm.c
@@ -495,7 +495,7 @@ static int snd_pcm_shm_drain(snd_pcm_t *pcm)
 	if (err < 0)
 		return err;
 	if (!(pcm->mode & SND_PCM_NONBLOCK))
-		snd_pcm_wait(pcm, -1);
+		snd_pcm_wait(pcm, SND_PCM_WAIT_DRAIN);
 	return err;
 }