EXTERNAL: Re: xorg.conf question

[Greene, Paul J.]

Thank you. That worked, or at least it gave me 3 working monitors. I'll follow up with a user and make sure that addressed his issue correctly.

And thanks for the link to the NVIDIA forum. Just to make sure, I'm not a developer - are user related questions acceptable on your developer forum?

From: Aaron Plattner <aplattner at nvidia.com>
Sent: Friday, March 5, 2021 1:07 AM
To: Greene, Paul J. <Greene-Paul at zai.com>; 'xorg at lists.x.org' <xorg at lists.x.org>
Subject: EXTERNAL: Re: xorg.conf question


These are NVIDIA-specific options so they're kinda offtopic here, but I'll try to address them below.

You might want to consider posting on the NVIDIA forum<https://forums.developer.nvidia.com/c/gpu-unix-graphics/linux/148> [1] or by emailing linux-bugs at nvidia.com<mailto:linux-bugs at nvidia.com>

[1] https://forums.developer.nvidia.com/c/gpu-unix-graphics/linux/148
On 3/4/21 9:36 AM, Greene, Paul J. wrote:
Hello,

First post on this list - don't be too hard on me.   :)

I support a bunch of software developers that use a KVM to switch back and forth between a Windows workstation and a CentOS 7.9 workstation. The Windows side has dual monitors, both going through the KVM, and the Linux side has 3 monitors - two monitors going through the KVM and the 3rd monitor connected directly to the PC.

In some cases, when they switch back and forth between the Windows PC and the Linux PC, the Linux PC loses its video resolution or 1 or more screens goes black. I'm assuming the video loses its sync with the monitor. To get out of this state, the user usually does a CTRL-ALT-BACKSPACE to restart X, or they go to CTRL-ALT-F2, login from the command prompt, and type "startx". In both cases they lose any unsaved work they've got open.

The video card (in most cases) is an NVIDIA 620 with the NVIDIA driver installed.

I've tried adding the following 4 lines to xorg.conf in the device section, and it seems to make only the left most monitor stable, but the other 2 monitors appear to be disabled, with black screens.

  Option         "ConnectedMonitor" "DFP-0"
  Option         "CustomEDID" "DFP-0:/etc/X11/edid.bin"
  Option         "IgnoreEDID" "false"
  Option         "UseEDID" "true"


If there's only one GPU in the system then you only need one Device section. It's likely that the other two device sections are ignored. ("Device" here refers to a GPU, not a physical display device).

The "ConnectedMonitor<https://download.nvidia.com/XFree86/Linux-x86_64/460.56/README/xconfigoptions.html#ConnectedMonitor>" option takes a comma-separated list of display devices that the driver should always consider connected. "CustomEDID<https://download.nvidia.com/XFree86/Linux-x86_64/460.56/README/xconfigoptions.html#CustomEDID>" uses a semicolon-separated list. So in your case you probably want this:

Option "ConnectedMonitor" "DP-0, DP-2, DP-6"
Option "CustomEDID" "DP-0:/path/to/edid0.bin; DP-2:/path/to/edid1.bin; DP-6:/path/to/edid2.bin"

These options are documented in the README: https://download.nvidia.com/XFree86/Linux-x86_64/460.56/README/xconfigoptions.html

You shouldn't need the IgnoreEDID or UseEDID options.
The system sees the 3 monitors as DP-2, DP-0, and DP-6 (respectively, from left to right). The NVIDIA driver includes a GUI configuration app that lets you generate the EDID files on each of the monitors, so I created an edid.bin file for each monitor, and adjusted the file path for each one in the 2nd line.

There's 3 device sections so I put the 4 lines above into each section (adjusting for edid.bin path and DP-x reference appropriately). That gave me one useable screen (the left one) - the middle and right monitor were black screens.

I tried putting the 4 lines all in one "Device" section, with the appropriate DP-x and edid.bin path, (total of 8 lines) and got the same result.



Options in xorg.conf don't combine when you have more than one of the same option in a section.

-- Aaron
The PCs are Dell Optiplex 9020s, if that's relevant.

Any suggestions? Am I on the right track here or should I be trying something else?

PG
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