Configuration: Laptop with Intel graphics, 24" monitor configured as primary display, laptop screen disabled, power button on laptop configured for shut down.
In most cases after initial power on part of the login screen will be displayed on the laptop LCD but the 24" monitor will remain blank. Login attempts will cause the laptop screen to go blank as desired but the external monitor won’t receive any display data - but it won’t display “no signal” either.
After shutdown of the laptop and subsequent restart (2x power button) in most cases the login will be displayed on both screens as expected and after login the laptop LCD will correctly be disabled. The other solution would be to unplugging and re-plugging the HDMI cable after a “blind” log in. Both solutions are most inconvenient. A software solution attempt by re-starting the display manager did not work.
So far I have used 2 different laptops, 3 different monitors and a bunch of HDMI cables without any success. Google suggests that this might be a kernel issue. This seems possible because the last working distro for me was Leap 42.2. I have decided to skip 42.3 due to the exact same problems hoping that Leap 15 might eventually get a fix.
I’d be most grateful for any advice how to avoid my double booting procedure.
Remarks: Favorite DE is KDE, but others (Mate, etc.) had the same problems. Win10 can handle all the 3 monitors tested without issues.
Do you always use this laptop with an external HDMI-connected monitor? Or is it just the case that you’d like to use it and disable the LVDS display when an external monitor is connected? You might be able to force the display and mode at boot with the ‘video=’ kernel parameter perhaps. For example (assuming HDMI-1 with monitor supporting 1920x1080)
Thanks for your advice regarding the “video=” parameter. Although it did not work it has lead me to an acceptable solution to avoid the double boot procedure:
I have configured grub2 for text display instead of graphics. After a few tries success rate was 100%, which means the graphical login screen will be displayed even on the external monitor. But I have no clue if grub2 or the kernels after Leap 42.2 are the culprits.
The only issue noticed in rare cases was that the wallpaper isn’t displayed after logging in so the background will stay black. But this is most likely not related to HDMI miscommunication. It suspiciously looks like one of those typical KDE/Plasma glitches.
To answer the question about my configuration:
I use laptops only because I don’t need the extra power of a desktop. The batteries are offering something like a UPS-like environment. The only display I am using is that of an external 24" monitor (1980x1200 as long as it can be bought).
Due to lack of time I’d leave it up to other users to file a bug if they are experiencing similar problems. The workaround mentioned above is sufficient for me.
As mentioned before, grub2 with text mode helps, but after several more boots success rate dropped slightly.
The whole thing strangely looks like uninitialized variables and/or registers.
Since the Redmonders lately appear to be more Linux friendly than ever they might eventually share their secret how to handle HDMI links properly >:)