Problems between XServer and Displaylink Docking Station

[Adam Nielsen]

> Once I login, the screen goes black for a minute or two, until all of
> the sudden my wallet-manager pops up. Other than that nothing else in my
> desktop environment seems to start, and it also seems to be quite slow.
> The next step is then to switch to TTY and then reboot the laptop.

I'm not sure whether you mean you switch to a TTY and reboot
intentionally because the laptop is so slow, or whether this happens
on its own without you doing anything.

If it happens automatically, it sounds like it could be the X server
crashing.  Without the DisplayLink device connected (when everything is
working fine) you could try running `killall X` to terminate the X
server and see if the laptop reboots.

If so then that removes the reboot as part of the problem and will put
it down to the X server terminating unexpectedly.

If terminating the X server does not trigger a reboot, it would be
interesting to find out why the machine reboots at all.

> I currently use the following configs in my X11/xorg.conf.d/
> 
> Section "Device"
>   Identifier "DisplayLink"
>   Driver "modesetting"
>   Option "PageFlip" "false"
> EndSection

This tells the X server to use whatever devices the kernel has grabbed
with the modesetting driver.  I believe it's the default and probably
has little effect.  It will also match the default onboard display
device too, even though it's not DisplayLink.

If you only want it to match the DisplayLink output you will need
something else in here to tell X that this config only applies to a
specific device and not all display devices it can find.  For normal
graphic devices this would be the "BusID" parameter, but I'm not sure
what you'd put here to match a DisplayLink device.

> It has worked fine and without any issues over the past years, and the
> problems started to occur with the version xorg-server 1.20.6.x at some
> point.

Has the DisplayLink driver also been updated in this time?  If you're
using the modesetting driver then I believe X won't be talking direct
to the hardware (just to the kernel interface, and the kernel talks to
the hardware) so in this case it seems very unlikely that a change in
the X server would be the root cause of the problem.  More likely one
of the kernel drivers.  You could always try going back to an older
kernel temporarily to see whether anything changes, and this is probably
easier than downgrading all the Xorg packages to try the same thing on
the userspace side.

> I am happy to provide any specific log files that would help
> troubleshoot this problem (Xorg.log or dmesg output or anything else).

The end of the Xorg.log is probably the most useful, assuming the X
server is terminating on its own.  No need to post the whole thing
(yet), just have a look at the end of it and see if you can find
anything that might explain why it's suddenly terminating.

The trick will be getting the log after X terminates but before the
machine reboots and writes a new log, by the sound of it.  You might be
able to get the previous log after reboot as Xorg.0.log.old though.

Cheers,
Adam.