3.18-stable review patch. If anyone has any objections, please let me know. ------------------ From: Manuel Reinhardt <manuel.rhdt@xxxxxxxxx> commit 2bc16b9f3223d049b57202ee702fcb5b9b507019 upstream. The commit a60945fd08e4 ("ALSA: usb-audio: move implicit fb quirks to separate function") introduced an error in the handling of quirks for implicit feedback endpoints. This commit fixes this. If a quirk successfully sets up an implicit feedback endpoint, usb-audio no longer tries to find the implicit fb endpoint itself. Fixes: a60945fd08e4 ("ALSA: usb-audio: move implicit fb quirks to separate function") Signed-off-by: Manuel Reinhardt <manuel.rhdt@xxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Takashi Iwai <tiwai@xxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- sound/usb/pcm.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) --- a/sound/usb/pcm.c +++ b/sound/usb/pcm.c @@ -311,6 +311,9 @@ static int search_roland_implicit_fb(str return 0; } +/* Setup an implicit feedback endpoint from a quirk. Returns 0 if no quirk + * applies. Returns 1 if a quirk was found. + */ static int set_sync_ep_implicit_fb_quirk(struct snd_usb_substream *subs, struct usb_device *dev, struct usb_interface_descriptor *altsd, @@ -370,7 +373,7 @@ add_sync_ep: subs->data_endpoint->sync_master = subs->sync_endpoint; - return 0; + return 1; } static int set_sync_endpoint(struct snd_usb_substream *subs, @@ -395,6 +398,10 @@ static int set_sync_endpoint(struct snd_ if (err < 0) return err; + /* endpoint set by quirk */ + if (err > 0) + return 0; + if (altsd->bNumEndpoints < 2) return 0;