Bug 368746

Summary:	System does not allow to enable external monitor after plugging into dock and crashes after unplug
Product:	[Plasma] KScreen	Reporter:	andreas.huelsing
Component:	common	Assignee:	Sebastian Kügler <sebas>
Status:	RESOLVED FIXED
Severity:	major
Priority:	NOR
Version First Reported In:	5.5.5
Target Milestone:	---
Platform:	Kubuntu
OS:	Linux
Latest Commit:		Version Fixed In:
Sentry Crash Report:

Description andreas.huelsing 2016-09-13 12:20:16 UTC

OS: 
Linux (x86_64) release 4.4.0-36-generic
KUbuntu 16.04.1 LTS

System:
Lenovo ThinkPad X240, model 20AMS21B00 
(graphics chip: Haswell-ULT Integrated Graphics Controller, driver: i915) 
Lenovo ThinkPad Pro Dock Type 40A1

Error:

When I plug the running system into my docking station, the system seems to detect everything fine: External USB drive is auto-mounted, LAN interface works, external keyboard and mouse work. Also, xrandr & systemsettings detect the external monitor which is connected to the DVI port of the dock. However, the external screen is not activated. 

Trying to enable the second screen via systemsettings makes the application hang and it only recovers after reverting the settings using the "external screen key" on the key board. 

After restarting the system / logging off it suddenly works: I can activate the external screen via systemsettings. When I make it the primary  display, the kde-dock sometimes does not switch to the primary display but this works after changing the configuration a few times.

Strangely, when I plug-in a beamer on the VGA port of the laptop, I can activate it without logging out / restart.

However, if I unplug the beamer from the VGA port or unplug the laptop from the dock, it crashes and only manually powering off the system works. 

The issue occurs every time I do the above.

The same system configuration worked perfectly fine with KUbuntu 14.04 LTS 

Reproducible: Always

Comment 1 Sebastian Kügler 2016-09-13 14:28:39 UTC

Thanks for the report!

Can you try Plasma 5.8, for example through Neon git/unstable? We have fixed a number of bugs that could lead to this problem, so it's most likely already fixed upstream. (I have similar hardware here, which didn't work well before and now is just fine.)

If you can verify it against 5.8, please reopen this bugreport and attach the information as outlined on https://community.kde.org/Solid/Projects/ScreenManagement#Debugging_Information