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<title>Workaround for broken TrackPoint</title>
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<p><a href="/">Index</a></p>
<h1>Workaround for broken TrackPoint</h1>
<small><time>2022-12-05</time></small>
<p>
Sometimes, seemingly at random after clicking the dedicated left click
or right click buttons, the buttons and trackpoint on my Lenovo
Thinkpad T14s stops working. Instead of clicking, the three mouse
buttons just makes the pointer move a bit and the trackpoint makes the
pointer move in a random direction and seems to issue clicks.
</p>
<p>
When this happens, the kernel buffer is spammed with "<code>psmouse
serio1: elantech: discarding packet</code>". Searching the interwebs,
I found that more people seem to be experiencing similar weirdness with
the elantech trackpoint driver.
</p>
<p>
Rebooting the computer works, but it's annoying. Removing and re-adding
the misbehaving kernel module resolves the issue too fortunately. I
put the following in <code>~/bin/fixmouse</code>:
<pre><code>#!/bin/sh
doas rmmod psmouse
doas modprobe psmouse
</pre></code>
So now I can run <code>fixmouse</code> whenever the driver stops
working.
</p>
<hr>
<p><i>Update 2023-09-24:</i> If the psmose module is builtin, it can't be
unloaded, giving "<code>rmmod: ERROR: Module psmouse is builtin.</code>"
Fortunately, there's a better way of reloading the trackpad using a
method described in an
<a href="https://lwn.net/Articles/143397/">article on LWN</a> from 2005.
</p>
<p>The error in the kernel buffer indicates that the trackpad is called
<code>serio1</code>, but for posterity we can find devices using the
<code>psmouse</code> driver with <code>find</code>:
<pre><code>$ find /sys/bus -name psmouse
/sys/bus/serio/drivers/psmouse
$ ls -l /sys/bus/serio/drivers/psmouse
total 0
--w-------. 1 root root 4096 Sep 23 22:19 bind
-rw-r--r--. 1 root root 4096 Sep 23 22:19 bind_mode
-r--r--r--. 1 root root 4096 Sep 23 22:19 description
lrwxrwxrwx. 1 root root 0 Sep 24 10:42 serio1 -> ../../../../devices/platform/i8042/serio1
--w-------. 1 root root 4096 Sep 23 14:20 uevent
--w-------. 1 root root 4096 Sep 24 10:36 unbind
</pre></code>
As described in the article, we can unbind the touchpad with (as root)
<pre><code>echo -n "serio1" > /sys/bus/serio/drivers/psmouse/unbind</pre></code>
My touchpad rebinds automatically after a few seconds, but you should be
able to bind it manually using
<code>[...]/psmouse/bind</code>.
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