[alsa-devel] [RFC PATCH 2/4] ALSA: core: add .notify callback for pcm ops

[Pierre-Louis Bossart]

When appl_ptr is updated let low-level driver know.

This is only enabled when the NO_REWIND hardware flag is used,
so that the low-level driver/hardware to opportunistically pre-fetch
data.

FIXME: should we rely on .ack for this?
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart at linux.intel.com>
---
 include/sound/pcm.h     |  2 ++
 sound/core/pcm_native.c | 18 +++++++++++++++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index 25310b7..d5eff03 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -87,6 +87,8 @@ struct snd_pcm_ops {
 			     unsigned long offset);
 	int (*mmap)(struct snd_pcm_substream *substream, struct vm_area_struct *vma);
 	int (*ack)(struct snd_pcm_substream *substream);
+	int (*notify)(struct snd_pcm_substream *substream);
+	/* FIXME: what's the difference between ack and notify ? */
 };
 
 /*
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index a70e52d..dd519b8 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -2565,6 +2565,10 @@ static snd_pcm_sframes_t snd_pcm_playback_forward(struct snd_pcm_substream *subs
 		appl_ptr -= runtime->boundary;
 	runtime->control->appl_ptr = appl_ptr;
 	ret = frames;
+
+	if (runtime->no_rewinds && substream->ops->notify)
+		substream->ops->notify(substream);
+
  __end:
 	snd_pcm_stream_unlock_irq(substream);
 	return ret;
@@ -2614,6 +2618,10 @@ static snd_pcm_sframes_t snd_pcm_capture_forward(struct snd_pcm_substream *subst
 		appl_ptr -= runtime->boundary;
 	runtime->control->appl_ptr = appl_ptr;
 	ret = frames;
+
+	if (runtime->no_rewinds && substream->ops->notify)
+		substream->ops->notify(substream);
+
  __end:
 	snd_pcm_stream_unlock_irq(substream);
 	return ret;
@@ -2713,8 +2721,16 @@ static int snd_pcm_sync_ptr(struct snd_pcm_substream *substream,
 			return err;
 	}
 	snd_pcm_stream_lock_irq(substream);
-	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_APPL))
+	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_APPL)) {
+		/* FIXME: this code is used by mmap_commit, should it handle boundary
+		 *   wrap-around as done for read/write in pcm_lib.c
+		 */
+
 		control->appl_ptr = sync_ptr.c.control.appl_ptr;
+		/* if supported, let low-level driver know about appl_ptr change */
+		if (runtime->no_rewinds && substream->ops->notify)
+			substream->ops->notify(substream);
+	}
 	else
 		sync_ptr.c.control.appl_ptr = control->appl_ptr;
 	if (!(sync_ptr.flags & SNDRV_PCM_SYNC_PTR_AVAIL_MIN))
-- 
1.9.1