Comment # 3 on bug 1200983 from Michael Hirmke

(In reply to Stefan Dirsch from comment #1)
> Hmm. Could you provide your Xserver logfile? Could be somewhere below
> ~/.local/share/sddm or alike. I'm afraid sddm no longer uses
> /var/log/Xorg.0.log. :-(

It is not sddm only. Sometimes the keyboard is working, so I can login. But in
plasma still the mouse does not work.
There are these error messages in Xorg.0.log:

[   125.027] (EE) Wacom HID 48EC Pen stylus: Invalid type 'cursor' for this
device.
[   125.027] (EE) Wacom HID 48EC Pen stylus: Invalid type 'touch' for this
device.
[   125.027] (EE) Wacom HID 48EC Pen stylus: Invalid type 'pad' for this
device.
...
[  5474.526] (EE) event4  - Fujitsu Siemens Computers SmartCard Keyboard USB
2A: client bug: event processing lagging behind by 22ms, your system is too
slow
...
[  7189.743] (EE) event4  - Fujitsu Siemens Computers SmartCard Keyboard USB
2A: WARNING: log rate limit exceeded (5 msgs per 60min). Discarding future
messages.