There is also a debug mode that manufacturers can use to send arbitrary debug data connections on the usb-C connections. (manufacturers used to do this over microUSB as well)
Another potential issue here is that if using the Pi as a client with a C-C cable this could confuse the device at the other end meaning it wont connect as it thinks it is being charged (will be seeing if I can get this to occur over the weekend).
Have just run this test and it does appear to confuse some USB-C ports (my phone and 3.0 usb-C port on my laptop detect the pi gadget however the 3.1 usb-C port doesn't detect the gadget if the pi is powered by gpio).
