We call ack callback whenever appl_ptr gets updated via
pcm_lib_apply_appl_ptr(). There are various code paths to call this
function. A part of them are for read/write/forward/rewind, where the
appl_ptr is always changed and thus the call of ack is mandatory.
OTOH, another part of code paths are from the explicit user call,
e.g. via SYNC_PTR ioctl. There, we may receive the same appl_ptr
value, and in such a case, calling ack is obviously superfluous.
This patch adds the check of the given appl_ptr value, and returns
immediately if it's no real update.
Signed-off-by: Takashi Iwai <tiwai@xxxxxxx>
---
sound/core/pcm_lib.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index e73b6e4135f6..75308ddc54ca 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -2112,6 +2112,9 @@ int pcm_lib_apply_appl_ptr(struct snd_pcm_substream *substream,
snd_pcm_uframes_t old_appl_ptr = runtime->control->appl_ptr;
int ret;
+ if (old_appl_ptr == appl_ptr)
+ return 0;
+
runtime->control->appl_ptr = appl_ptr;
if (substream->ops->ack) {
ret = substream->ops->ack(substream);
--
2.13.1
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