ALSA: usb-audio: Avoid implicit feedback on Pioneer devices
For addressing the regression on Pioneer devices, we recently corrected the quirk code to enable the implicit feedback mode on those devices properly. However, the devices still showed problems with the full duplex operations with JACK, and after debug sessions, we figured out that the older kernels that had worked with JACK also didn't use the implicit feedback mode at all although they had the quirk code to enable it; instead, the old code worked just to skip the normal sync endpoint setup that would have been detected without it. IOW, what broke without the implicit-fb quirk in the past was the application of the normal sync endpoint that is actually the capture data endpoint on these devices. This patch covers the overseen piece: it modifies the quirk code again not to enable the implicit feedback mode but just to make the driver skipping the sync endpoint detection. This made the driver working with JACK full-duplex mode again. Still it's not quite clear why the implicit feedback doesn't work on those devices yet; maybe it's about some issues in the URB setup. But at least, with this patch, the driver should work in the level of the older kernels again. Fixes: 167c9dc8 ("ALSA: usb-audio: Fix implicit feedback sync setup for Pioneer devices") Link: https://lore.kernel.org/r/20210118075816.25068-4-tiwai@suse.de Signed-off-by:Takashi Iwai <tiwai@suse.de>
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