I hope this is an acceptable place to ask this question. I've spend a
bit of time reverse-engineering the USB protocol for a subset of
Blackmagic Design video mixers and I have made a userspace
implementation to make these devices usable in Linux with libusb. This
is working great but the roadblock I have that I can't find a reasonable
solution for is that these devices also expose an UVC webcam.
While my control software is active it's not possible to use the UVC
webcam functionality of the device because with libusb I have to detach
the kernel from the interfaces to make my userspace access work. As far
as I can find documented online there's no way to have half a composite
device handled by kernel drivers and half with userspace drivers in
Linux. It seems to me the only solution is to make a kernel driver to
bind to the control interface and have that kernel driver pass-through
to userspace somehow with a custom protocol? If that is the case would
such a driver even be supported in Linux?
For reference the device I'm working has these looks like this:
USB 1-4 [1edb:be55] Blackmagic design Blackmagic Design [serial]
Class EF SubClass 02 Protocol 01
Interface 0 FF/03/00 Unknown <- Blackmagic USB configuration protocol
Interface 1 FF/02/00 Unknown <- Blackmagic USB control protocol
(I'm using this with libusb)
Interface 2 FF/04/00 Unknown <- Unknown
Interface 3 FE/01/01 Unknown <- DFU
Interface 4 0E/01/01 Blackmagic Design <- UVC camera
Interface 5 0E/02/01 Unknown <- UVC camera
Interface 6 01/01/00 Blackmagic Design <- ALSA
Interface 7 01/02/00 Unknown <- ALSA
If this is not the right place for this question, then where would the
right place be?
Greetings,
Martijn Braam
