How to know which file in /dev/input/event* represent for touch input device

Question

I have a raspberry pi3 and one 7" official lcd and have code to get data from touch input, but when I plug a keyboard into the RPI the touch device is event2, and event0 when keyboard is unplugged. So how do I determine which event is represent for touch?

Answer 1

Look at /dev/input/by-id and /dev/input/by-path, or check out the output of lsinput, or

udevadm info --query=property --name=/dev/input/eventX

Note that xinput seems to use its own IDs which don't always correspond to /dev/input/eventX.

Answer 2

install:

apt install input-utils

and issue

lsinput

this will list all your input devices along with some information about each device