Re: [alsa-devel] ALSA:usb audio Higher sample rates on usb audio no longer working.

[Pierre-Louis Bossart]

On 1/4/19 10:52 AM, Gopal, Saranya wrote:
> > > [ 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
> The current detection logic is that UAC3 configuration is chosen only when a device has a configuration with audio interface supporting UAC3 protocol.
> Additionally, it already makes sure that UAC3 is selected only when there is more than one configuration.
What I meant if that the other configurations are not checked for UAC1 
or UAC2 capabilities, you only check that there is more than one 
configuration