Re: [PATCH v23 32/32] ASoC: doc: Add documentation for SOC USB

[Pierre-Louis Bossart <pierre-louis.bossart@xxxxxxxxxxxxxxx>]

>> Just so I understand...is it really desired that userspace doesn't
>> have the flexibility to choose which USB device is offloaded?  I know
>> it complicates what needs to be done, but it could be just an
>> additional feature that can be added later on.  Again, by default, we
>> select the last USB headset plugged in to be enabled for offload by
>> default.
> 
> If it chooses endpoint by itself perhaps you can send patch set without
> controls first? This has added benefit of less patches in series, making
> it easier to review and it won't block whole patch set by discussion on
> controls feature. Controls can be added in followup series.

We do need read-only controls for userspace to know that offload is
possible and which card/device to use. That can be done in a first step
assuming there's a single device plugged-in.

Dealing with multiple devices and defining rules or configuration
options to select the offloaded device is a second-level problem.

In most cases the only thing that will be offloaded is a headset
anyways, so the selection could be rather static based on a
vendor/system ID, all other USB devices would be ignored.