xorg.conf question

[Greene, Paul J.]

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"

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.

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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