How to annotate USB jacks without jack detection?

[Kai-Heng Feng]

Hi,

There are some UAC1 devices come with jacks, but without jack detection 
ability. And many USB/Thunderbolt docks are equipped with such USB 
device.

Userspace like PulseAudio automatically switch to USB audio when they 
gets plugged. However, auto-switching to UAC1 device can be problematic 
because it may not connected to any headset or speaker.

So I wonder what's the best way to let userspace know the USB device is 
a jack without jack detection ability? Through sysfs or dedicated UCM 
conf?

Kai-Heng