Source

configurations / 10-synaptics.conf

Section "InputClass"
        Identifier "touchpad catchall"
        Driver "synaptics"
        MatchIsTouchpad "on"
        MatchDevicePath "/dev/input/event*"
        Option "TouchpadOff" "1"
	Option "TapButton1" "1"
        Option "TapButton2" "2"
        Option "TapButton3" "3"
EndSection