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#1 2021-05-31 10:33:38

Registered: 2020-12-09
Posts: 1

Unable to hot-plug a second monitor, black screen


As the title says, I get a black screen and what seems to be a system crash when I try to plug any monitor on the HDMI port of my laptop when it’s turned on. I searched several times on the internet to see if this problem was known, but either I didn’t search with the right keywords, or I’m searching for something that has not been identified at the moment, the fact remains that I didn’t find any relevant solutions or problems.
I, then, did several tests to try to determine in which cases this problem exactly happens and if I could identify the source of the it. The blank black screen, as the system crashes, affect both monitors.

Here’s a short but probably relevant list of information about my laptop and Linux installation:
OS: Arch Linux x86_64
Host: VivoBook 12_ASUS Laptop E203MAS_E203MA 1.0
Kernel: 5.12.7-arch1-1
Resolution: 1366x768
DE: Plasma 5.21.5
WM: KWin
CPU: Intel Pentium Silver N5000 (4) @ 2.700GHz
GPU: Intel UHD Graphics 605

* I don’t have any of these problems on the same machine with Windows 10.
* I encounter this problem both on and Wayland.
* As I can’t switch to a new tty and can’t control anything, either with KdeConnect or ssh, and as when the screens becomes black, all audio streams (on speaker or jack line out) are stopped, I think we can consider that it’s not only a crash but a crash of almost the whole system.
* However, when my phone is connected with Bluetooth to my laptop, the system/bluez/KDE-with-bluedevil automatically routes the phone’s audio streams to the laptop’s audio output. This way, I found by accident that when the system crashes, the audio streams from my phone are still read on the laptop audio output used before the crash (e.g. plugging in headphones on the jack port stops the sound of the speakers but doesn’t switch to the headphones, and unplugging it restore the sound on speakers).
Maybe things are directly routed from BT device to the laptop’s BT chip to the laptop’sound chip then to the laptop’speakers/jack line, so nothing pass through the system and thus stops when it crashes…
* Going into the Kde’s display settings (or using another X/RandR configuration tool like LxRandR or aRandR) and disabling the external screen to enable it again is the equivalent of hot-plugging the screen,
* There is no problems when unplugging the monitor: the entire display switches to the laptop builtin monitor and I can continue using it as usual, without rebooting,
* it crashes too when I plug the monitor after the `Starting·Finished Load/Save Screen Backlight Brightness of backlight:intel_backlight` log line during boot is shown, BUT I can un·plug the screen in SDDM as many times I want, and SDDM will just choose the smallest resolution between the monitors and use it to render the display on both monitor (e.g. a 1920×1080 monitor will display at my laptop’s 1366×768 resolution, and a 1280×720 monitor will make my laptop’s render at the monitor’s resolution)
* I thought it was kscreen’s fault and that disabling it would solve things but in fact it didn’t changed a lot of things, and even made some things worse:
    — I still have to plug the monitor before the boot or in SDDM,
    — but when unplugging the external monitor, the screen layout’s auto-config is not made anymore: the display remains the same as with the external monitor plugged in, so windows and cursor still display on this second screen and I can move them… blindly :D
    — If I plug the monitor in SDDM when kscreen is disabled, the external monitor is not automatically enabled.
    — Next, if I enable kscreen again, it enables automatically the second monitor then the system crashes. However, when kscreen is disabled but I plug in the monitor before the boot, both monitor will display the same things (with the resolution of both screens being the one of the smaller screen, as already said in the upper brackets), and enabling kscreen will automatically and properly set the resolution and placement of both screens, according to the previously chosen settings, without any crash.

So the thing is that I just need to plug the screen at boot to not encounter any problems, but it is really not convenient, and the problem really seems to be when enabling a new monitor.

I really don’t know what logs of which programs or tool I can look at to investigate deeper, so I surely need the help from the Arch community to solve this.

Have a nice day,


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