gamepads won't work at all

[Abion47]

If the pads are x-input pads (i.e. Xbox pads), then they should just work. Otherwise, it's very much a "your mileage may vary" situation, and you might need to use software to map them to either x-input or to keyboard controls.

Alternatively, you could just use the keyboard and mouse. SOMA isn't really a game that requires a controller to get the "full experience", and in some ways, I'd say it actually makes some things more difficult.