Do you have any idea how it compares (performance-wise) to USBIP (http://usbip.sourceforge.net/ also in the Linux Kernel)?
No, we actually did no formal performance benchmarks, but we use it quite heavily for multiplayer emulation games, and so far everyone was very satisfied with latency, responsiveness and general controller-feel. Very interesting point though, I’d like to do that some time!
One feature that I imagine is hard to do with USBIP is filtering the input - since we don’t want people using their keyboard/mouse on the gaming rig, we filter for the gamepad axes and buttons, which works a treat!
In addition, we can use non-USB devices on the client (e.g. PS/2) and even non-devices (the repo contains the slightly out-of-date osc-xlater, which translates a set of OSC messages sent by eg. a smartphone into a gamepad emulation). I also believe our approach requires fewer privileges in comparison to USBIP, as we can run with user privileges for both components if configured correctly.