A patent by Valve has been unearthed showing off a controller that could be for their rumored "Steambox".
The image in the patent shows off what seems to be a gamepad with the usual buttons and sticks, with one twist: those can be swapped out and replaced with such controls like trackpads. The pad will automatically detect the new input/output of the new components and adjust accordingly.
The patent was filed in 2009 and published in 2011.
The current rumor is that Valve will be unveiling the "Steambox" either this week at Game Developers Conference or in June during E3 2012.