I was doing an experiment with my raspberry pi, and I needed a joystick of some sort for input. Only thing I had lying around was a ps4 controller. Plugged it in, used pygame for input, all was good but I couldn't figure out the touch pad.

Eventually I noticed that the mouse cursor was moving. Turns out that Linux automatically recognises the touch pad on that controller as hid mouse like device, with pushing for clicks and all. Immediately my life got easier, it's much better than a touchscreen.

I don't know why I hadn't heard of this, because it's awesome.