A dirty fix for non-stop drifting Trackpoint

The problem

[...] PROBLEM: The cursor always slowly moves to the lower left. One pixel every few seconds¹.[...]

I had the exact same issue²: painfully slowly drifting Trackpoint on my X250, never stopping. I'm aware of the Trackpoint self-calibration, I had that on the X200, on the T400, and on the T500, but this was different. If you have the pointer moving fast or just rarely on it's own, that is normal. In my case, it never stopped.

The really surprising thing was that this only happened under Debian Stretch (RC2) and not under Ubuntu 16.04, so I started looking around /sys:

Note: it's probably serio2, but could be 3, 4, etc., depending on module load order and number of input devices.

# ls /sys/devices/platform/i8042/serio1/serio3
bind_mode    driver       id       mindrag          protocol    resolution   speed      upthresh
description  drvctl       inertia  modalias         rate        resync_time  subsystem  ztime
draghys      ext_dev      input    power            reach       sensitivity  thresh
drift_time   firmware_id  jenks    press_to_select  resetafter  skipback     uevent

Most of these are pretty much undocumented and so far none of the GUI configuration managers supported them. The 3 interesting ones are drift_time, sensitivity, and speed in this case.

Despite this fix, this is most probably a hardware problem, so consider replacing the keyboard, especially if it's still under warranty, though if it doesn't happen under Windows, this will be near impossible to get through the service.

Temporary fix

Most will recommend to lower the sensitivity, but that doesn't always work or help.

echo 2 > /sys/devices/platform/i8042/serio1/serio2/drift_time
echo 180 > /sys/devices/platform/i8042/serio1/serio2/sensitivity
echo 50 > /sys/devices/platform/i8042/serio1/serio2/speed

Keep it after reboot

systemd-tmpfiles --prefix=/sys --create
sensible-editor /etc/tmpfiles.d/trackpoint.conf

w /sys/devices/platform/i8042/serio1/serio2/speed - - - - 50
w /sys/devices/platform/i8042/serio1/serio2/sensitivity - - - - 180
w /sys/devices/platform/i8042/serio1/serio2/drift_time - - - - 2

```

UPDATE (2019-02-14 20:12)

The path has changed:

w /sys/devices/rmi4-00/rmi4-00.fn03/serio3/speed - - - - 180
w /sys/devices/rmi4-00/rmi4-00.fn03/serio3/sensitivity - - - - 120
w /sys/devices/rmi4-00/rmi4-00.fn03/serio3/drift_time - - - - 2

(Oh, by the way: this entry was written by Peter Molnar, and originally posted on petermolnar dot net.)