Commit 932a8151 authored Feb 13, 2019 by Ricardo Biehl Pasquali Committed by Takashi Iwai Feb 13, 2019

ALSA: pcm: Comment why read blocks when PCM is not running



This avoids bringing back the problem introduced by
62ba568f ("ALSA: pcm: Return 0 when size <
start_threshold in capture") and fixed in 00a399ca
("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 <pasqualirb@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

parent 5a23f385

sound/core/pcm_lib.c

+4 −0

Original line number	Diff line number	Diff line
		@@ -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) {