From 932a81519572156a88dbc2349d183c603446f9c4 Mon Sep 17 00:00:00 2001 From: Ricardo Biehl Pasquali Date: Wed, 13 Feb 2019 00:57:51 -0200 Subject: [PATCH] ALSA: pcm: Comment why read blocks when PCM is not running This avoids bringing back the problem introduced by 62ba568f7aef ("ALSA: pcm: Return 0 when size < start_threshold in capture") and fixed in 00a399cad1a0 ("ALSA: pcm: Revert capture stream behavior change in blocking mode"), which prevented the user from starting capture from another thread. Signed-off-by: Ricardo Biehl Pasquali Signed-off-by: Takashi Iwai --- sound/core/pcm_lib.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/sound/core/pcm_lib.c b/sound/core/pcm_lib.c index bcb06bd3d81d..345ab1ab2cac 100644 --- a/sound/core/pcm_lib.c +++ b/sound/core/pcm_lib.c @@ -2176,6 +2176,10 @@ snd_pcm_sframes_t __snd_pcm_lib_xfer(struct snd_pcm_substream *substream, if (runtime->status->state == SNDRV_PCM_STATE_RUNNING) snd_pcm_update_hw_ptr(substream); + /* + * If size < start_threshold, wait indefinitely. Another + * thread may start capture + */ if (!is_playback && runtime->status->state == SNDRV_PCM_STATE_PREPARED && size >= runtime->start_threshold) { -- 2.30.2