Gitweb:     http://git.kernel.org/linus/ae1ec5e1e97f67d41e641a73380129e5905e41cc
Commit:     ae1ec5e1e97f67d41e641a73380129e5905e41cc
Parent:     4bbe1ddf89a5ba3ec30fe5980912d8bda3a3cbb2
Author:     Takashi Iwai <tiwai@suse.de>
AuthorDate: Mon Oct 13 03:08:53 2008 +0200
Committer:  Takashi Iwai <tiwai@suse.de>
CommitDate: Tue May 5 14:47:21 2009 +0200

    ALSA: usbaudio - Add delay account
    
    Manage the PCM delay account based on the queued URBs.
    
    Signed-off-by: Takashi Iwai <tiwai@suse.de>
---
 sound/usb/usbaudio.c |   14 +++++++++++++-
 1 files changed, 13 insertions(+), 1 deletions(-)

diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index 823296d..6c25fa2 100644
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -627,6 +627,7 @@ static int prepare_playback_urb(struct snd_usb_substream *subs,
 	subs->hwptr_done += offs;
 	if (subs->hwptr_done >= runtime->buffer_size)
 		subs->hwptr_done -= runtime->buffer_size;
+	runtime->delay += offs;
 	spin_unlock_irqrestore(&subs->lock, flags);
 	urb->transfer_buffer_length = offs * stride;
 	if (period_elapsed)
@@ -636,12 +637,22 @@ static int prepare_playback_urb(struct snd_usb_substream *subs,
 
 /*
  * process after playback data complete
- * - nothing to do
+ * - decrease the delay count again
  */
 static int retire_playback_urb(struct snd_usb_substream *subs,
 			       struct snd_pcm_runtime *runtime,
 			       struct urb *urb)
 {
+	unsigned long flags;
+	int stride = runtime->frame_bits >> 3;
+	int processed = urb->transfer_buffer_length / stride;
+
+	spin_lock_irqsave(&subs->lock, flags);
+	if (processed > runtime->delay)
+		runtime->delay = 0;
+	else
+		runtime->delay -= processed;
+	spin_unlock_irqrestore(&subs->lock, flags);
 	return 0;
 }
 
@@ -1520,6 +1531,7 @@ static int snd_usb_pcm_prepare(struct snd_pcm_substream *substream)
 	subs->hwptr_done = 0;
 	subs->transfer_done = 0;
 	subs->phase = 0;
+	runtime->delay = 0;
 
 	/* clear urbs (to be sure) */
 	deactivate_urbs(subs, 0, 1);
--
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