ALSA: pcm: add SNDRV_PCM_TRIGGER_DRAIN trigger

Add SNDRV_PCM_TRIGGER_DRAIN trigger for pcm drain.

Some audio devices require notification of drain events
in order to properly drain and shutdown an audio stream.
Signed-off-by: Libin Yang <libin.yang@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/pcm.h

@@ -106,6 +106,7 @@ struct snd_pcm_ops {
 #define SNDRV_PCM_TRIGGER_PAUSE_RELEASE	4
 #define SNDRV_PCM_TRIGGER_SUSPEND	5
 #define SNDRV_PCM_TRIGGER_RESUME	6
+#define SNDRV_PCM_TRIGGER_DRAIN		7
 
 #define SNDRV_PCM_POS_XRUN		((snd_pcm_uframes_t)-1)
 

include/uapi/sound/asound.h

@@ -268,6 +268,7 @@ typedef int __bitwise snd_pcm_subformat_t;
 #define SNDRV_PCM_INFO_SYNC_START	0x00400000	/* pcm support some kind of sync go */
 #define SNDRV_PCM_INFO_NO_PERIOD_WAKEUP	0x00800000	/* period wakeup can be disabled */
 #define SNDRV_PCM_INFO_HAS_WALL_CLOCK   0x01000000      /* has audio wall clock for audio/system time sync */
+#define SNDRV_PCM_INFO_DRAIN_TRIGGER	0x40000000		/* internal kernel flag - trigger in drain */
 #define SNDRV_PCM_INFO_FIFO_IN_FRAMES	0x80000000	/* internal kernel flag - FIFO size is in frames */
 
 typedef int __bitwise snd_pcm_state_t;

sound/core/pcm_native.c

@@ -420,7 +420,8 @@ int snd_pcm_hw_refine(struct snd_pcm_substream *substream,
 
 	hw = &substream->runtime->hw;
 	if (!params->info) {
-		params->info = hw->info & ~SNDRV_PCM_INFO_FIFO_IN_FRAMES;
+		params->info = hw->info & ~(SNDRV_PCM_INFO_FIFO_IN_FRAMES |
+					    SNDRV_PCM_INFO_DRAIN_TRIGGER);
 		if (!hw_support_mmap(substream))
 			params->info &= ~(SNDRV_PCM_INFO_MMAP |
 					  SNDRV_PCM_INFO_MMAP_VALID);
@@ -1566,6 +1567,13 @@ static int snd_pcm_do_drain_init(struct snd_pcm_substream *substream, int state)
 			snd_pcm_post_stop(substream, new_state);
 		}
 	}
+
+	if (runtime->status->state == SNDRV_PCM_STATE_DRAINING &&
+	    runtime->trigger_master == substream &&
+	    (runtime->hw.info & SNDRV_PCM_INFO_DRAIN_TRIGGER))
+		return substream->ops->trigger(substream,
+					       SNDRV_PCM_TRIGGER_DRAIN);
+
 	return 0;
 }