Options for forcing display output?

tarian · 2023-05-29 06:27:15

Hi all,

First post here, give me feedback if needed.

I am looking for options to force display output on. I am using this command:

 echo on > /sys/kernel/debug/dri/0/OUTPUT/force

currently but it doesn't reliably stay on.

Context:

I am setting up a virtual monitor on my device so I can use steam link (steam remote play) to use my laptop as a second monitor for this device.

I got my xrandr settings finalized and after reading through this wiki article: https://wiki.archlinux.org/title/Extrem … DMI_output was able to test everything using the display output force command listed.

I used

 # echo on > /sys/kernel/debug/dri/0/OUTPUT/force

to force the output on my virtual display using the extra display out I am not using (DP-1). Everything works great while the force output setting is applied.

My only problem now is something is periodically setting the force output setting to off making using that method of forcing display output an unreliable way for me to achieve what I am trying to do.

Relevant specs:
I have an AMD APU.
1 DP display out via usb-c (DP-1/DisplayPort-0) and 1 screen display (eDP)

Skidout · 2023-05-29 22:57:11

Can you run the command again after the display has started? If so, try (watch -n 0.1 "echo on > /sys/kernel/debug/dri/0/OUTPUT/force"). 0.1 is in seconds, so the command would execute every 100 milliseconds. Might not be the most elegant solution, and you might lag for up to 100 milliseconds if whatever is unforcing it times perfectly with the command. Unfortunately, watch can only execute commands every 0.1 seconds minimum.

Last edited by Skidout (2023-05-29 22:57:32)

seth · 2023-05-30 06:50:23

https://wiki.archlinux.org/title/Audit_ … ies_access the path to see what writes it.
The cause might be https://wiki.archlinux.org/title/Displa … _Signaling so you could try to disable that or outright disable the extension, https://man.archlinux.org/man/extra/xor … NS_SECTION

Do you use a DM (like and especially GDM)?

tarian · 2023-05-31 17:13:01

Skidout wrote:

Can you run the command again after the display has started? If so, try (watch -n 0.1 "echo on > /sys/kernel/debug/dri/0/OUTPUT/force"). 0.1 is in seconds, so the command would execute every 100 milliseconds. Might not be the most elegant solution, and you might lag for up to 100 milliseconds if whatever is unforcing it times perfectly with the command. Unfortunately, watch can only execute commands every 0.1 seconds minimum.

I will see, I am actually getting permission denied (even with sudo) when echoing into that force file but if I edit the file with nano it will take the change.

seth wrote:

https://wiki.archlinux.org/title/Audit_ … ies_access the path to see what writes it.
The cause might be https://wiki.archlinux.org/title/Displa … _Signaling so you could try to disable that or outright disable the extension, https://man.archlinux.org/man/extra/xor … NS_SECTION
Do you use a DM (like and especially GDM)?

I will run that audit and see if I can track down what is editing it. Thanks for the link on Display Signaling I will also see if disabling that will work. I am using SSDM (Simple Desktop Display Manager).

tarian · 2023-05-31 19:23:05

Ok figured out what is causing the display to turn back off:

[drm:amdgpu_dm_connector_mode_valid [amdgpu]] *ERROR* No EDID firmware found on connector: DP-1 ,forcing to OFF!

So it looks like I have to fake EDID firmware info for my virtual display or somehow disable this check.

Maybe a dummy monitor will work? http://www.bictor.com/2017/08/15/instal … y-monitor/

Just need to figure out adding the config for my actual display so it doesn't go black.

seth · 2023-05-31 19:40:54

https://wiki.archlinux.org/title/Kernel … s_and_EDID

Arch Linux

#1 2023-05-29 06:27:15

Options for forcing display output?

#2 2023-05-29 22:57:11

Re: Options for forcing display output?

#3 2023-05-30 06:50:23

Re: Options for forcing display output?

#4 2023-05-31 17:13:01

Re: Options for forcing display output?

#5 2023-05-31 19:23:05

Re: Options for forcing display output?

#6 2023-05-31 19:40:54

Re: Options for forcing display output?

Board footer