ALSA: Add extra delay count in PCM

Added runtime->delay field to adjust the delayed samples for snd_pcm_delay().
Typically a hardware FIFO length is stored in this field, so that the
extra delay between hwptr and applptr can be computed.
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/pcm.h

@@ -270,6 +270,7 @@ struct snd_pcm_runtime {
 	snd_pcm_uframes_t hw_ptr_base;	/* Position at buffer restart */
 	snd_pcm_uframes_t hw_ptr_interrupt; /* Position at interrupt time */
 	unsigned long hw_ptr_jiffies;	/* Time when hw_ptr is updated */
+	snd_pcm_sframes_t delay;	/* extra delay; typically FIFO size */
 
 	/* -- HW params -- */
 	snd_pcm_access_t access;	/* access mode */

sound/core/pcm_native.c

@@ -587,14 +587,15 @@ int snd_pcm_status(struct snd_pcm_substream *substream,
 	if (substream->stream == SNDRV_PCM_STREAM_PLAYBACK) {
 		status->avail = snd_pcm_playback_avail(runtime);
 		if (runtime->status->state == SNDRV_PCM_STATE_RUNNING ||
-		    runtime->status->state == SNDRV_PCM_STATE_DRAINING)
+		    runtime->status->state == SNDRV_PCM_STATE_DRAINING) {
 			status->delay = runtime->buffer_size - status->avail;
-		else
+			status->delay += runtime->delay;
+		} else
 			status->delay = 0;
 	} else {
 		status->avail = snd_pcm_capture_avail(runtime);
 		if (runtime->status->state == SNDRV_PCM_STATE_RUNNING)
-			status->delay = status->avail;
+			status->delay = status->avail + runtime->delay;
 		else
 			status->delay = 0;
 	}
@@ -2404,6 +2405,7 @@ static int snd_pcm_delay(struct snd_pcm_substream *substream,
 			n = snd_pcm_playback_hw_avail(runtime);
 		else
 			n = snd_pcm_capture_avail(runtime);
+		n += runtime->delay;
 		break;
 	case SNDRV_PCM_STATE_XRUN:
 		err = -EPIPE;