DRM connector for external monitor has name card1-eDP-1

I recently received a ddcutil bug report that came down to the fact that an external DisplayPort connected monitor had DRM connector name card1-eDP-1 instead of something like card1-DP-1. I have been relying on "eDP" in the connector name to indicate that the display in question is an Embedded Display Port device, (almost?) always a laptop display, that does not support DDC. Is naming the connector for an external display in this way valid, or is it a bug?

motherboard: Acer Predator G3-605 PC CPU: Intel i7-4790 using integrated video motherboard video connectors: DP, HDMI, VGA monitor: AOC model 24G2W1G4, connected using DP

Interestingly, the primary video controller is reported as having vid:pid 8086:0412, which pci.ids interprets as "Xeon E3-1200 v3/4th Gen Core Processor Integrated Graphics Controller"

The monitor is known to support DDC.

Kernel: 6.7.6-arch1-1

There is no corresponding /boot/config file for this kernel.

I will ask the user who reported this problem to add themself to the CC list for this possible bug.

changed the description

I don't see a way to add myself, so i'm just writing this comment :D

Please boot with log_buf_len=4M drm.debug=0xe passed to kernel cmdline, and attach the resulting dmesg.

Also attach a copy of /sys/kernel/debug/dri/0/i915_vbt

added Community label

Here are the corresponding files
i915_vbt
dmesg.log

For whatever reason, the VBT says the device has an eDP port.

Presumably the biggest problem with this VBT is that if you boot without DP connected then the eDP connector will not be registered at all, and thus the DP port won't be usable.

What do you have in BIOS Boot Options menu for "Launch CSM" and "Launch Video OPROM"?

Can you try without CSM, without legacy Video OPROM?

If I boot without DP connected, then it shows DP-1 as available (and eDP-1 is not registered) and if I connect the cable, it now shows it at DP-1 instead of eDP-1. If I disable CSM and boot with the DP cable connected, it is now registered as DP-1 from the beginning, so I guess that solves this problem.

Huh. Sounds like the VBIOS modifies the VBT based on whether anything is connected or not. That is surprising. Can you attach a copy of the VBT when booted in legacy mode without DP connected?

But yeah legacy boot is known to be crap on many HSW+ machines. So if things work correctly in EFI mode then I guess we're pretty much done here.

Sure thing.

Here is the VBT with CSM enabled and DP disconnected: i915_vbt_csm_not_connected

For comparison, here is the VBT with CSM disabled: i915_vbt_no_csm

Also: the first time I restarted after enabling CSM, neither eDP-1 nor DP-1 got registered and when connecting the cable, nothing happened (the VBT file was identical with the one I posted earlier). After another reboot, I couldn't replicate it, maybe it had something to do with the timing of disconnecting the cable after enabling CSM and booting.

added feature: display/VBT label

added feature: display/DP feature: display/eDP labels

Thanks for the bug report @rockowitz and @d4ve10. I think we're just going to close this if it works by disabling CSM and going with EFI mode. CSM or legacy boot is just known to often be buggy and untested, and life's too short to debug issues in there.

Closing. Please don't hesitate to reopen or file new issues if the problem persists or you have new ones.

closed