Modern USB gadget on Linux and how to integrate it with systemd (Part 2)

After the descriptors and strings are written, FunctionFS creates appropriate number of ep files for you to use to implement the desired data streams between the host and the device. c The file also contains an example of how to specify USB descriptors and strings to be written to ep0 to make FunctionFS ready. And here the systemd’s lazy daemon start comes into play: the descriptors and strings are already passed to FunctionFS, so it becomes ready _but_ the daemon is _not_ started until some traffic directed at this FunctionFS instance happens on USB.

Source: www.collabora.com