[PATCH] ALSA: pcm: fix incorrect hw_base increase

Brent Lu
2020-05-15T04:15:49Z

The hw_base will be increased by runtime->buffer_size frames
unconditionally if the runtime->status->hw_ptr is not updated for over
half of buffer time. As the hw_base increases, so does the
runtime->status->hw_ptr which could lead to invalid return value when
user space program calls snd_pcm_avail() function.

By updating runtime->hw_ptr_jiffies each time the HWSYNC is called,
the hw_base will keep the same when buffer stall happens, so does the
hw_ptr.

Signed-off-by: Brent Lu <brent.lu@intel.com>
---
sound/core/pcm_lib.c | 1 +
1 file changed, 1 insertion(+)

diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c
index 872a852..d531e1b 100644
--- a/sound/core/pcm_lib.c
+++ b/sound/core/pcm_lib.c
@@ -433,6 +433,7 @@ static int snd_pcm_update_hw_ptr0(struct snd_pcm_substream *substream,

no_delta_check:
if (runtime->status->hw_ptr == new_hw_ptr) {
+ runtime->hw_ptr_jiffies = curr_jiffies;
update_audio_tstamp(substream, &curr_tstamp, &audio_tstamp);
return 0;
}
--
2.7.4