Dell Latitude 7480 pointingstick acceleration too fast

English Hardware
1

Hello

I installed OpenSuse Leap 15.0 on a Dell Latitude 7480. However, the pointingstick (the blue “dot” in the middle of the keyboard) has too high acceleration for any precise movements.

It appears that there is a file called /usr/lib/udev/hwdb.d/70-pointingstick.hwdb where the acceleration is tuned down for many laptops, however mine is not in the list. I tried to fix the issue on my own, but without any success. This is what I did:

I created a new file called 71-pointingstick-latitude.hwdb in the same directory with the following contents (i adapted the contents from 70-pointingstick.hwdb):

evdev:name:*DualPoint Stick:dmi:bvn*:bvr*:bd*:svnDellInc.:pnLatitude7480*:pvr*
 POINTINGSTICK_CONST_ACCEL=0.1

I got the device name (pnLatitude7480) by reading the modalias:

$ cat /sys/class/dmi/id/modalias        
dmi:bvnDellInc.:bvr1.10.1:bd05/28/2018:svnDellInc.:pnLatitude7480:pvr:rvnDellInc.:rn00F6D3:rvrA00:cvnDellInc.:ct10:cvr:

Afterwards I ran to following for updating:

sudo systemd-hwdb update
sudo udevadm trigger

However, like I said above, this did not solve the issue. What I am I doing wrong?
Thanks in advance!

2

Your desktop environment might reset it, From what I’ve read, setting the mouse speed should affect the pointing stick ( FWIW IMO a horrible invention ). My first thoughts btw would not go to udev, rather to some conf file in /etc/X11/xorg.conf.d

3

Some thoughts: Is the evdev name you used for matching correct? You could use ‘xinput’ or ‘sudo libinput list-devices’ to check that. Assuming that is ok, then I also wondered about experimenting with the POINTINGSTICK_SENSITIVITY variable as well. That can influence the speed greatly.

BTW, this is a good reference for libinput issues
https://wayland.freedesktop.org/libinput/doc/latest/
In particular, the FAQ section. It may also be necessary to post a bug report to get this resolved if you can’t do it as a user.

FWIW, I wanted to share this bug report not because it refers to your exact Dell model, but because it is a good illustration of quirks with pointing devices, and involves Peter Hutterer (libinput developer) so a very interesting, representative discussion on the subject.

4

As Knurpht mentioned, your DE may be influencing the device behaviour as well. Which DE are you using?

5

Thank you for your replies.

I am using KDE Plasma 5. And indeed, reducing the mouse acceleration in my DE seems to also reduce acceleration of the pointing stick, while also making my USB mouse unusable in the process.

While Googling I found this bug report: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1657553. The following command (taken from the the bug report) seems to slow the pointing stick down without influencing any other pointing device, so I can run the command on startup as a workaround. Also it probably proves Knurpht’s theory that the DE is resetting the acceleration.

xinput set-prop 'DualPoint Stick' 'libinput Accel Speed' 0.1

However, what seems to be the actual problem with making precise movements and becomes more visible with a lower acceleration, is that the cursor movements seem to be clipping to the X and Y axis while using the pointing stick. It is really visible while doing precise movements. For example, when I open a drawing program and try to draw a small circle, I end up with an almost perfect square, with perfectly straight sides. The effect is not that visible with less precise movements (like large circles for example). I did not have time to research this issue currently, but it looks like a bug in the driver (or somewhere around there) to me.

6

Yes, it would seem to be the case. A bug report is the only way forward here.

7

BTW, can you show us all the properties available for that pointing device?

xinput list-props 'DualPoint Stick'