Mouse ThinkPad X1 Mouse on /dev/input/event20
Move the device 250mm/10in or more along the x-axis.
Pause 3 seconds before movement to reset, Ctrl+C to exit.
Covered distance in device units:      462 at frequency 20000.0Hz 	\^C
Estimated sampling frequency: 20000Hz
To calculate resolution, measure physical distance covered
and look up the matching resolution in the table below
      29mm	    1.16in	     400dpi
      19mm	    0.77in	     600dpi
      14mm	    0.58in	     800dpi
      11mm	    0.46in	    1000dpi
       9mm	    0.39in	    1200dpi
       8mm	    0.33in	    1400dpi
       7mm	    0.29in	    1600dpi
       6mm	    0.26in	    1800dpi
       5mm	    0.23in	    2000dpi
       5mm	    0.21in	    2200dpi
       4mm	    0.19in	    2400dpi
If your resolution is not in the list, calculate it with:
	resolution=462/inches, or
	resolution=462 * 25.4/mm

Entry for hwdb match (replace XXX with the resolution in DPI):
mouse:bluetooth:v17efp6088:name:ThinkPad X1 Mouse:
 MOUSE_DPI=XXX@20000