[alsa-devel] [PATCH 3/9] pcm: handle negative values from snd_pcm_mmap_hw_avail

[Alexander E. Patrakov]

Such negative values can happen when an underrun happens and xrun
detection is disabled. Another situation is if the device updated the
pointer before alsa-lib has a chance to detect the xrun.

The problem is that these negative values could propagate to the
snd_pcm_rewindable return value, where it is specified that negative
returns must be interpreted as error codes and not as negative amount of
samples.

Signed-off-by: Alexander E. Patrakov <patrakov at gmail.com>
---
 src/pcm/pcm_dmix.c   |  2 +-
 src/pcm/pcm_dshare.c |  4 +---
 src/pcm/pcm_hw.c     |  2 +-
 src/pcm/pcm_ioplug.c |  2 +-
 src/pcm/pcm_local.h  | 18 ++++++++++++++++++
 src/pcm/pcm_plugin.c |  2 +-
 6 files changed, 23 insertions(+), 7 deletions(-)

diff --git a/src/pcm/pcm_dmix.c b/src/pcm/pcm_dmix.c
index ffde12a..babde6a 100644
--- a/src/pcm/pcm_dmix.c
+++ b/src/pcm/pcm_dmix.c
@@ -661,7 +661,7 @@ static int snd_pcm_dmix_pause(snd_pcm_t *pcm ATTRIBUTE_UNUSED, int enable ATTRIB
 
 static snd_pcm_sframes_t snd_pcm_dmix_rewindable(snd_pcm_t *pcm)
 {
-	return snd_pcm_mmap_hw_avail(pcm);
+	return snd_pcm_mmap_playback_hw_rewindable(pcm);
 }
 
 static snd_pcm_sframes_t snd_pcm_dmix_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t frames)
diff --git a/src/pcm/pcm_dshare.c b/src/pcm/pcm_dshare.c
index f1a1a1d..020e6f7 100644
--- a/src/pcm/pcm_dshare.c
+++ b/src/pcm/pcm_dshare.c
@@ -412,7 +412,7 @@ static int snd_pcm_dshare_pause(snd_pcm_t *pcm ATTRIBUTE_UNUSED, int enable ATTR
 
 static snd_pcm_sframes_t snd_pcm_dshare_rewindable(snd_pcm_t *pcm)
 {
-	return snd_pcm_mmap_playback_hw_avail(pcm);
+	return snd_pcm_mmap_playback_hw_rewindable(pcm);
 }
 
 static snd_pcm_sframes_t snd_pcm_dshare_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t frames)
@@ -420,8 +420,6 @@ static snd_pcm_sframes_t snd_pcm_dshare_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t
 	snd_pcm_sframes_t avail;
 
 	avail = snd_pcm_dshare_rewindable(pcm);
-	if (avail < 0)
-		return 0;
 	if (frames > (snd_pcm_uframes_t)avail)
 		frames = avail;
 	snd_pcm_mmap_appl_backward(pcm, frames);
diff --git a/src/pcm/pcm_hw.c b/src/pcm/pcm_hw.c
index 74cff67..c34b766 100644
--- a/src/pcm/pcm_hw.c
+++ b/src/pcm/pcm_hw.c
@@ -659,7 +659,7 @@ static int snd_pcm_hw_pause(snd_pcm_t *pcm, int enable)
 
 static snd_pcm_sframes_t snd_pcm_hw_rewindable(snd_pcm_t *pcm)
 {
-	return snd_pcm_mmap_hw_avail(pcm);
+	return snd_pcm_mmap_hw_rewindable(pcm);
 }
 
 static snd_pcm_sframes_t snd_pcm_hw_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t frames)
diff --git a/src/pcm/pcm_ioplug.c b/src/pcm/pcm_ioplug.c
index 85a8891..fe9347c 100644
--- a/src/pcm/pcm_ioplug.c
+++ b/src/pcm/pcm_ioplug.c
@@ -503,7 +503,7 @@ static int snd_pcm_ioplug_pause(snd_pcm_t *pcm, int enable)
 
 static snd_pcm_sframes_t snd_pcm_ioplug_rewindable(snd_pcm_t *pcm)
 {
-	return snd_pcm_mmap_hw_avail(pcm);
+	return snd_pcm_mmap_hw_rewindable(pcm);
 }
 
 static snd_pcm_sframes_t snd_pcm_ioplug_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t frames)
diff --git a/src/pcm/pcm_local.h b/src/pcm/pcm_local.h
index 74ebd60..394505f 100644
--- a/src/pcm/pcm_local.h
+++ b/src/pcm/pcm_local.h
@@ -464,6 +464,24 @@ static inline snd_pcm_sframes_t snd_pcm_mmap_hw_avail(snd_pcm_t *pcm)
 	return pcm->buffer_size - snd_pcm_mmap_avail(pcm);
 }
 
+static inline snd_pcm_sframes_t snd_pcm_mmap_playback_hw_rewindable(snd_pcm_t *pcm)
+{
+	snd_pcm_sframes_t ret = snd_pcm_mmap_playback_hw_avail(pcm);
+	return (ret >= 0) ? ret : 0;
+}
+
+static inline snd_pcm_sframes_t snd_pcm_mmap_capture_hw_rewindable(snd_pcm_t *pcm)
+{
+	snd_pcm_sframes_t ret = snd_pcm_mmap_capture_hw_avail(pcm);
+	return (ret >= 0) ? ret : 0;
+}
+
+static inline snd_pcm_uframes_t snd_pcm_mmap_hw_rewindable(snd_pcm_t *pcm)
+{
+	snd_pcm_sframes_t ret = snd_pcm_mmap_hw_avail(pcm);
+	return (ret >= 0) ? ret : 0;
+}
+
 static inline const snd_pcm_channel_area_t *snd_pcm_mmap_areas(snd_pcm_t *pcm)
 {
 	if (pcm->stopped_areas &&
diff --git a/src/pcm/pcm_plugin.c b/src/pcm/pcm_plugin.c
index a607ccf..c19e2f1 100644
--- a/src/pcm/pcm_plugin.c
+++ b/src/pcm/pcm_plugin.c
@@ -198,7 +198,7 @@ static int snd_pcm_plugin_reset(snd_pcm_t *pcm)
 
 static snd_pcm_sframes_t snd_pcm_plugin_rewindable(snd_pcm_t *pcm)
 {
-	return snd_pcm_mmap_hw_avail(pcm);
+	return snd_pcm_mmap_hw_rewindable(pcm);
 }
 
 snd_pcm_sframes_t snd_pcm_plugin_rewind(snd_pcm_t *pcm, snd_pcm_uframes_t frames)
-- 
2.1.0