SUMMARY External monitor on a Displaylink device is not recognized by Plasma-Wayland (but it does work with Plasma-Xorg) STEPS TO REPRODUCE 1. install and start the displaylink driver https://www.displaylink.com/downloads/file?id=1576 2. reboot 3. log-in selecting Plasma-Wayland 4. plug-in an external monitor on the Displaylink device OBSERVED RESULT Monitor is not recognized (neither by xrandr nor by Plasma Screen configuration) EXPECTED RESULT external monitor should be recognized, as it is with Plasma-Xorg SOFTWARE/OS VERSIONS Linux/KDE Plasma: Neon User Edition 5.19 KDE Plasma Version: 5.19.4 KDE Frameworks Version: 5.73.0 Qt Version: 5.14.2 ADDITIONAL INFORMATION Dell XPS 13 laptop with USB Displaylink extension (including audio, ethernet, and HDMI for external monitors)
With 5.21 we have multi-gpu support - as DisplayLink is AFAIK recognized as a GPU it might work now, as long as you have it connected on boot (hotplugging shouldn't be difficult but isn't implemented yet). So please test again :) Also, what does ls /dev/dri/ output, with and without the displaylink device being connected?
WOW! it works! Thanks! Now I can set different scalings to monitors with very different resolutions, and move a window from one to the other while the window appears more or less the same on both! (that is, not like twice smaller on one monitor). I've been waiting for this moment for soooo long ;) Here is the output of $ ls /dev/dri/ by-path card0 card1 card2 card3 card4 renderD128 (while monitor is connected). If I disconnect it, I have the same.
Cool! > Here is the output of $ ls /dev/dri/ >by-path card0 card1 card2 card3 card4 renderD128 >(while monitor is connected). If I disconnect it, I have the same. That's quite interesting, I don't assume you have 4 GPUs installed, so the driver apparently creates multiple devices... I also assumed that the card device would get dynamically added and removed by the kernel, apparently not so then. Did you try hot-unplugging? If it doesn't remove the cardX device then it most likely won't crash. Also, does hotplugging work if you don't plug it in at boot?
yes, the displaykink driver seems to give me 4 screens: $ ls /dev/dri/by-path/ pci-0000:00:02.0-card pci-0000:00:02.0-render platform-evdi.0-card platform-evdi.1-card platform-evdi.2-card platform-evdi.3-card
Thanks! I think them support for DisplayLink should be complete; if there are remaining issues then just open a new bug report