I’ve been looking at how Consumer Control keys are processed, and I’m wondering if I’ve found something vestigial, but I’m not sure. In key_defs.h, there are several constants defined that get included in the high byte of the Key objects in key_defs_consumerctl.h:
These don’t appear to be used anywhere; those bits get stripped by the CONSUMER() macro in the HID façade, and I haven’t seen any code that looks for those HID usage types. Also, the bits used overlap the IS_CONSUMER bit — though that should perhaps simply be moved from bit 4 to bit 6, which is otherwise unused, as far as I can see (as long as the RESERVED bit is not set).