Comment 105 for bug 549447

(In reply to comment #24)
> This fixes nothing for the Xorg driver situation which
> is currently not very good since evdev support for
> touchscreens is missing e.g. calibration

fwiw, man evdev(4)

Evdev Axis Calibration
              4 32-bit values, order min-x, max-x, min-y, max-y or 0
              values to disable run-time axis calibration. This feature
              is required for devices that need to scale to a different
              coordinate system than originally reported to the X
              server, such as touchscreens that require run-time cali-
              bration.

xinput --set-int-prop "My Device" "Evdev Axis Calibration" 32 0 10 20 30 for example calibrates your touchscreen at runtime if the actual range is 0-10 on x and 20-30 on y.