The fix commit the commit e4ea77f8e53f ("ALSA: usb-audio: Always apply the hw constraints for implicit fb sync") tried to address the bug where an incorrect PCM parameter is chosen when two (implicit fb) streams are set up at the same time. This change had, however, some side effect: once when the sync endpoint is chosen and set up, this restriction is applied at the next hw params unless it's freed via hw free explicitly.
This patch is a workaround for the problem by relaxing the hw constraints a bit for the implicit fb sync. We still keep applying the hw constraints for implicit fb sync, but only when the matching sync EP is being used by other streams.
Fixes: e4ea77f8e53f ("ALSA: usb-audio: Always apply the hw constraints for implicit fb sync") Link: https://lore.kernel.org/r/4e509aea-e563-e592-e652-ba44af6733fe@veniogames.co... Signed-off-by: Takashi Iwai tiwai@suse.de --- sound/usb/pcm.c | 9 +++++++-- 1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/sound/usb/pcm.c b/sound/usb/pcm.c index 7fc95ae9b2f0..2fd4ecc1b25a 100644 --- a/sound/usb/pcm.c +++ b/sound/usb/pcm.c @@ -937,8 +937,13 @@ get_sync_ep_from_substream(struct snd_usb_substream *subs) continue; /* for the implicit fb, check the sync ep as well */ ep = snd_usb_get_endpoint(chip, fp->sync_ep); - if (ep && ep->cur_audiofmt) - return ep; + if (ep && ep->cur_audiofmt) { + /* ditto, if the sync (data) ep is used by others, + * this stream is restricted by the sync ep + */ + if (ep != subs->sync_endpoint || ep->opened > 1) + return ep; + } } return NULL; }