Another step forward! These are my controllers default calibration values:
jscal -s 18,1,0,112,142,5534751,5534751,1,0,112,142,5534751,5534751,1,0,112,142,5534751,5534751,1,0,112,142,5534751,5534751,1,0,112,142,5534751,5534751,1,0,112,142,5534751,5534751,1,0,0,0,536870912,536870912,1,0,0,0,536870912,536870912,1,255,-4208,3952,21931,21931,1,255,-4208,3952,21931,21931,1,255,-4208,3952,21931,21931,1,63,-1023,1023,87367,87367,1,63,-1023,1023,87367,87367,1,63,-1023,1023,87367,87367,1,0,0,0,0,0,1,0,960,960,559240,559240,1,0,471,471,1139853,1139853,1,0,32767,32767,16384,16384 /dev/input/js0
And this pacifies the gyroscope's axis. I don't need them and they cause endless events if not "deadzoned":
jscal -s 18,1,0,112,142,5534751,5534751,1,0,112,142,5534751,5534751,1,0,112,142,5534751,5534751,1,0,112,142,5534751,5534751,1,0,112,142,5534751,5534751,1,0,112,142,5534751,5534751,1,0,0,0,536870912,536870912,1,0,0,0,536870912,536870912,1,255,0,0,0,0,1,255,0,0,0,0,1,255,0,0,0,0,1,255,0,0,0,0,1,255,-0,0,0,0,1,255,0,0,0,0,1,0,0,0,0,0,1,0,960,960,559240,559240,1,0,471,471,1139853,1139853,1,0,32767,32767,16384,16384 /dev/input/js0
Unfortunately there is no way to calibrate /dev/iput/event0, but /dev/input/js0 (jstest /dev/input/js0) is completely silent now if the gamepad isn't in use. This should be good enough for me, as even SDL might be forced to use /dev/input/js0 (export SDL_JOYSTICK_DEVICE=/dev/input/js0).
Next step would be to recognize for how long /dev/input/js0 showed no action. Any ideas?