[PATCH alsa-lib 4/4] pcm: hw: introduce SNDRV_PCM_HW_PARAMS_DRAIN_SILENCE

[Jaroslav Kysela <perex@xxxxxxxx>]

The application may not require to touch the sample stream
for the drain operation at all. Handle this situation
in alsa-lib.

Signed-off-by: Jaroslav Kysela <perex@xxxxxxxx>
---
 include/sound/uapi/asound.h |  3 +++
 src/pcm/pcm.c               | 32 ++++++++++++++++++++++++++++++++
 src/pcm/pcm_hw.c            |  3 ++-
 src/pcm/pcm_local.h         |  1 +
 4 files changed, 38 insertions(+), 1 deletion(-)

diff --git a/include/sound/uapi/asound.h b/include/sound/uapi/asound.h
index 0b8834f2..f970179e 100644
--- a/include/sound/uapi/asound.h
+++ b/include/sound/uapi/asound.h
@@ -390,6 +390,9 @@ typedef int snd_pcm_hw_param_t;
 #define SNDRV_PCM_HW_PARAMS_NORESAMPLE	(1<<0)	/* avoid rate resampling */
 #define SNDRV_PCM_HW_PARAMS_EXPORT_BUFFER	(1<<1)	/* export buffer */
 #define SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP	(1<<2)	/* disable period wakeups */
+#define SNDRV_PCM_HW_PARAMS_NO_DRAIN_SILENCE	(1<<3)	/* supress drain with the filling
+							 * of the silence samples
+							 */
 
 struct snd_interval {
 	unsigned int min, max;
diff --git a/src/pcm/pcm.c b/src/pcm/pcm.c
index 099d83ee..5872ee6f 100644
--- a/src/pcm/pcm.c
+++ b/src/pcm/pcm.c
@@ -4958,6 +4958,38 @@ int snd_pcm_hw_params_get_period_wakeup(snd_pcm_t *pcm, snd_pcm_hw_params_t *par
 	return 0;
 }
 
+/**
+ * \brief Restrict a configuration space to allow the drain with the filling of silence samples
+ * \param pcm PCM handle
+ * \param params Configuration space
+ * \param val 0 = disable, 1 = enable (default) drain with the filling of silence samples
+ * \return 0 otherwise a negative error code
+ */
+int snd_pcm_hw_params_set_drain_silence(snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int val)
+{
+	assert(pcm && params);
+	if (val)
+		params->flags &= ~SND_PCM_HW_PARAMS_NO_DRAIN_SILENCE;
+	else
+		params->flags |= SND_PCM_HW_PARAMS_NO_DRAIN_SILENCE;
+	params->rmask = ~0;
+	return snd_pcm_hw_refine(pcm, params);
+}
+
+/**
+ * \brief Extract drain with the filling of silence samples from a configuration space
+ * \param pcm PCM handle
+ * \param params Configuration space
+ * \param val 0 = disable, 1 = enable
+ * \return 0 otherwise a negative error code
+ */
+int snd_pcm_hw_params_get_drain_silence(snd_pcm_t *pcm, snd_pcm_hw_params_t *params, unsigned int *val)
+{
+	assert(pcm && params && val);
+	*val = params->flags & SND_PCM_HW_PARAMS_NO_DRAIN_SILENCE ? 0 : 1;
+	return 0;
+}
+
 /**
  * \brief Extract period time from a configuration space
  * \param params Configuration space
diff --git a/src/pcm/pcm_hw.c b/src/pcm/pcm_hw.c
index ea0c2ef2..90d5d07a 100644
--- a/src/pcm/pcm_hw.c
+++ b/src/pcm/pcm_hw.c
@@ -399,7 +399,8 @@ static int snd_pcm_hw_hw_params(snd_pcm_t *pcm, snd_pcm_hw_params_t * params)
 	params->info &= ~0xf0000000;
 	if (pcm->tstamp_type != SND_PCM_TSTAMP_TYPE_GETTIMEOFDAY)
 		params->info |= SND_PCM_INFO_MONOTONIC;
-	hw->perfect_drain = !!(params->info & SND_PCM_INFO_PERFECT_DRAIN);
+	hw->perfect_drain = !!(params->info & SND_PCM_INFO_PERFECT_DRAIN) ||
+			    !!(params->flags & SND_PCM_HW_PARAMS_NO_DRAIN_SILENCE);
 	return query_status_data(hw);
 }
 
diff --git a/src/pcm/pcm_local.h b/src/pcm/pcm_local.h
index b039dda0..abea6654 100644
--- a/src/pcm/pcm_local.h
+++ b/src/pcm/pcm_local.h
@@ -107,6 +107,7 @@
 #define SND_PCM_HW_PARAMS_NORESAMPLE SNDRV_PCM_HW_PARAMS_NORESAMPLE
 #define SND_PCM_HW_PARAMS_EXPORT_BUFFER SNDRV_PCM_HW_PARAMS_EXPORT_BUFFER
 #define SND_PCM_HW_PARAMS_NO_PERIOD_WAKEUP SNDRV_PCM_HW_PARAMS_NO_PERIOD_WAKEUP
+#define SND_PCM_HW_PARAMS_NO_DRAIN_SILENCE SNDRV_PCM_HW_PARAMS_NO_DRAIN_SILENCE
 
 #define SND_PCM_INFO_MONOTONIC	0x80000000
 
-- 
2.39.2