Comment 3 for bug 1715271

commit 293b915fd9bebf33cdc906516fb28d54649a25ac
Author: Oscar Campos <email address hidden>
Date: Tue Jul 18 17:20:36 2017 -0700

    Input: trackpoint - assume 3 buttons when buttons detection fails

    Trackpoint buttons detection fails on ThinkPad 570 and 470 series,
    this makes the middle button of the trackpoint to not being recogized.
    As I don't believe there is any trackpoint with less than 3 buttons this
    patch just assumes three buttons when the extended button information
    read fails.

    Signed-off-by: Oscar Campos <email address hidden>
    Acked-by: Peter Hutterer <email address hidden>
    Signed-off-by: Dmitry Torokhov <email address hidden>

This 2nd need to be merged to ubuntu kernel.