The complete handling on the control interface is currently dead.
We return with EOPNOTSUPP for the caller to know that a response
to such requests is not valid. The host however may ask
control interface why these control requests were not available.
For this the UVC_VC_REQUEST_ERROR_CODE_CONTROL is used. As an overall
exception for the control interface we just always return 0x06 as
an response which is representing "not implemented".
This patch is a necessary feature to properly pass the UVC Functionality
Test of the USB3CV Compliance Software.
Fixes: 69c17461392d ('uvcgadget: Properly implement GET_INFO control responses')
Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/7524>
3b345568bc