Hardware Using other controllers with PS3?

[retrospect]

I read somewhere that the PS3 has support for "non-PlayStation controllers" and they identify as such when connected. The PS4 controller did this for example when connected to a PS3.

Will the original Xbox controllers work if plugged in via USB?
Will the MayFlash Wii U Gamecube Adaptor work, since it doesn't need drivers on PC?
Will other Direct Input devices work?

Cheers