Does Linux support this? I am trying to connect my laptop to a monitor via USB C. The laptop has two Thunderbolt ports and the monitor has support for USB C DP alt mode. I have tested the same setup on my work laptop (windows 11) and it works fine but my laptop running arch does not work. My laptop detects the monitor correctly so it shows up in the KDE plasma display configuration but the monitor is not getting any input. As far as I could tell this is supported in the kernel. Am I wrong? Am I missing some important package?
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Works ootb on fedora kde wayland.
Is your usb c dp connected to a gpu other than the one the compositor running on? Does the screen show in display settings? Setting different configurations and refresh rate works?
It has to do with muxing for the dGPU. I have bashed my head against this what seems like endlessly. My suggestion is that you should enable only dedicated gpu mode in your bios. That has worked for me. It kind of sucks because you feel like you are leaving performance on the table, but I have found nothing that works properly on any DE in any configuration.
At the end of the day it is basically a hardware issue, and for your specific hardware it will not work. I’m my limited opinion.
What does dmesg say when you plug it in?
What’s the model, just for starters
Right sorry forgot to mention that. The laptop is an Asus Vivobook S14 K3402Z (not the OLED one in case that matters). The monitor is a Philips Evnia 49M2C8900
Do you have the bolt and plasma-thunderbolt packages installed? I believe I had to do that to use a thunderbolt SSD enclosure/docks with my laptop. I am not sure about DP alt mode, though.
Yes those are both installed
do you have evdi installed? and if not, does it work when you reboot with the cable connected?
No I don’t have that installed. Isn’t DisplayLink something completely different?
Rebooting while connected sorta worked, but not really. When I logged in the laptop monitor went black and the external monitor was black with a white underscore at the top left as if a terminal was open. So that’s something I guess but I could not use my computer at all in this state.
yeah displaylink is sort of a streaming feature, but evdi is a kernel module that makes the kernel aware of multiple monitors over usb (among other things), it’s required for display plug-n-play over usb in my experience.
It is not required for the displayport alternate mode of usb-c.
It is an alternative with limited performance that is built on top of usb and does not require hardware support on the PC side.
good to know, i’ve never managed to get it working without. what’s the recommended approach then?
If your monitor/docking station/adapter and the computer support the DP Alternate mode, then you should use that, it should be supported directly by the kernel. Problems may occur if the port is connected to the dedicated graphics and you use the internal graphics card. In my experience it worked perfectly so I do not know any good troubleshooting steps.
then, maybe it was added to the kernel after i first tried it and i’ve been working with old assumptions.
also that behavior is interesting because it means the display is detected and the computer is drawing to it but something in your environment is unstable. check the system log for previous boot to see what screwed up.
My laptop detects the monitor correctly so it shows up in the KDE plasma display configuration but the monitor is not getting any input.
So the system thinks it’s enabled? Can you move the mouse cursor to it?
Exactly. No I can’t move my mouse to the external monitor.
Works fine. I use it on my XPS 13 daily with Fedora 41
