quoted

... Unfortunately, this means I screwed up the Wii U ProController
ABI. Anyhow, this just means we continue to have 0 compatible gamepad
drivers in the kernel. User-space needs to fix them up, anyway, as all
other gamepads are also incompatible.

I know it is not really relevant and you won't fix the kernel interface
anyway, but I was just curios: is there any known userspace using the
gamepad API?

SDL are talking about 'fixing things'.... just in-case we're breaking it
(again) for them
http://lists.libsdl.org/pipermail/sdl-libsdl.org/2013-November/091850.html

Simon