This article describes the basics about USB protocol enough to overcome my usual fear of dappling into USB hacking. The author demonstrated the means to use libusb (user-space) to interact with an unsupported USB RGB light.

xDCI is a specification that includes features to allow programming a USB port to emulate a USB device. This article talks about kernel hardware support, BIOS flashing, PCH (Platform Controller Hub), PMC (Power Management Controller), NVRAM, efivars, and finally how to use the author's Raw Gadget tools to emulate USB devices.