4 Jan
2019
4 Jan
'19
4:23 p.m.
[ 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.
-Pierre