Re: [alsa-devel] ALSA:usb audio Higher sample rates on usb audio no longer working.
From: Pierre-Louis Bossart
Date: Fri Jan 04 2019 - 10:23:45 EST
[ Adding linux-usb ML to Cc, as it's a core USB issue ]
So the device seems incorrectly advertising as if it were supporting
UAC3 -- assuming the device is still not UAC3-capable.
IOW, it's a buggy firmware. We need some blacklisting, or revert the
commit for now, unless any real UAC3 device comes up to the market.
IIRC an UAC3-capable device is required to expose a backwards-compatible
configuration (either UAC1 or UAC2). Maybe an additional test can be
done to harden the detection so that UAC3 is only chosen if indeed a
second audio configuration is present as well.
I also vaguely recall there was talk about adding information in the BOS
descriptor, but I don't know if this was ever published.