[colejohnson66]

I sounds to me that it works like an interface. You call function `doFoo()` and if there's a foobar, the OS does foo. If there isn't a foobar, the method does nothing (but both return STATUS_FOO_SUCCESS).

For the touch bar, you aren't doing the actual rendering; the OS is. Only the OS knows if there's a touch bar, so without a kext or something, it seems there's no way for you to know if the touch bar exists.

[dom0]

Rendering and uploading something (or sending some messages to the touch bar controller; or queuing messages to the touch bar) probably takes a tiny bit longer than

    if(!touchbar) return MAKE_SUCCESS_GREAT_AGAIN;

But then again maybe the user space component just doesn't have that conditional.