[PATCH] ALSA: usb-audio: disable implicit feedback sync for Behringer UFX1204 and UFX1604

[Geraldo Nascimento]

Hi Takashi,

Hopefully you will be able to apply this cleanly to branch master of your
sound.git.

Thanks!
Geraldo Nascimento

---

Behringer UFX1204 and UFX1604 have Synchronous endpoints to which
current ALSA code applies implicit feedback sync as if they were
Asynchronous endpoints. This breaks UAC compliance and is unneeded.

The commit 5e35dc0338d85ccebacf3f77eca1e5dea73155e8 and subsequent
1a15718b41df026cffd0e42cfdc38a1384ce19f9 were meant to clear up noise.

Unfortunately, noise persisted for those using higher sample rates and
this was only solved by commit d2e8f641257d0d3af6e45d6ac2d6f9d56b8ea964

Since there are no more reports of noise, let's get rid of the
implicit-fb quirks breaking UAC compliance.

Signed-off-by: Geraldo Nascimento <geraldogabriel at gmail.com>

diff --git a/sound/usb/implicit.c b/sound/usb/implicit.c
index 23767a14d126..70319c822c10 100644
--- a/sound/usb/implicit.c
+++ b/sound/usb/implicit.c
@@ -54,8 +54,6 @@ static const struct snd_usb_implicit_fb_match playback_implicit_fb_quirks[] = {
 
 	/* Fixed EP */
 	/* FIXME: check the availability of generic matching */
-	IMPLICIT_FB_FIXED_DEV(0x1397, 0x0001, 0x81, 1), /* Behringer UFX1604 */
-	IMPLICIT_FB_FIXED_DEV(0x1397, 0x0002, 0x81, 1), /* Behringer UFX1204 */
 	IMPLICIT_FB_FIXED_DEV(0x2466, 0x8010, 0x81, 2), /* Fractal Audio Axe-Fx III */
 	IMPLICIT_FB_FIXED_DEV(0x31e9, 0x0001, 0x81, 2), /* Solid State Logic SSL2 */
 	IMPLICIT_FB_FIXED_DEV(0x31e9, 0x0002, 0x81, 2), /* Solid State Logic SSL2+ */