*working with xrandr 1.5 not finding how to connect second or third gpu*
------------------------------
Greetings

Running debian buster (testing) using lxqt. Have 3 nvidia 570 gpus and 4
1920x1080 monitors.
Have had this system now for almost 5.5 years and have had it running the
four monitors all that time.

Updated to buster (new testing) and found that there were some issues with
proprietary drivers nvidia 375.66 - - - was having one gpu halt and upon
reboot things seemed to work again.

The time between reboots was getting down to less than 12 hrs when I landed
up with a system with corrupted networking on a reboot.
So in the process of re-install I decided to try the Nouveau drivers
instead. So now I have a one gpu 2 monitor system available. Got to very
much like the four monitors for my work layout so I want the other two
monitors working.

Using xrandr I can see Provider 0,1 and 2.
DVI-I-1 and DVI-I-2 are connected.
DVI-I-2-5 and DVI-I-2-6 are listed as disconnected.

I have been able to create a virtual screen of 3840 x 3000 which is how I
had things before this reinstall
using $xrandr --fb 3840x3000 .
Tried $xrandr --setprovideroutputsource 1 0
no changes
looked for pci addresses
found 01:00.0. 02:00.0 and 03:00.0

Looked in the kernel log and all I can see is a error code of -19 (for both
Provider 1 and 2) which, after a lot of digging, seems to be saying "no
such device"
Tried $ xrandr --addmode DVI-I-2-5 1920x1080
then DVI-I-2-5 still shows as disconnected but with a resolution of
1920x1080 60.00
Next I tried $ xrandr --output VGA-2 --mode 1920x1080 --pos 1280x1280
--rotate inverted
result - - warning: output VGA-2 not found; ignoring

It used to be that this setup happened in xorg.conf (and was a monolithic
file), then things were changed to files placed in /etc/xorg.conf.d (as
individual descriptions - - - ie. devices, monitors and AIUI screens) and
in my system these kind of files are now in /etc/X11/Xsession.d but there
aren't any to do with graphics issues.

Any information I haven't provided that would help others help me?

I can't find any guides on how to setup xrandr to use multiple gpus AND
more than 2 or 3 monitors (usually from only 1 gpu).
Most of the randr information I can find is for at newest randr 1.3 and I
have 1.5. Randr 1.4 is where the multiple gpu option was introduced so it
should be possible but . . . .

I've found
https://cgit.freedesktop.org/xorg/pr...oto-1.5.0#n160
likely everything I need is hidden in this file but for the life of me I
can't figure out what commands to use. If I were an expert I wouldn't be
asking but I'm not and there are no examples to follow (or try).

Suggestions please?

(Maybe do I have to go for newer proprietary drivers? (rather not I sort of
like the no issues right now with Nouveau!)

TIA

Dee
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