How to switch to a particular resolution? Xorg complains "No valid modes for "DFP-1:2560x1600"; removing." and ignores my setting.

[Pete Wright]

On 9/23/20 12:44 AM, Yuri wrote:
> Xorg for me starts with the resolution 1920x1080.
>
> I know that 2560x1600 is supported because the NVidia settings program 
> can switch to 2560x1600 by typing 2560x1600 into it. The window 
> manager stays in a square with the size 1920x1080, and the extra space 
> appears around it.
>
>
> But how to change xorg.conf in order to make 2560x1600 a default 
> resolution?
>
>
> I tried to add the line Modes into this section:
>
>         SubSection "Display"
>                 Viewport   0 0
>                 Depth     1
>                 Modes      "2560x1600" "1920x1080"
>         EndSubSection
>
> But Xorg fails to accept the 2560x1600 value with this warning:
>
> [  9995.669] (WW) NVIDIA(0): No valid modes for "DFP-1:2560x1600"; 
> removing.
>
> and still uses 1920x1080.
>
>

I would run xrandr after X has started (even at the incorrect 
resolution) and grep for 2560 - it should give you the specific 
resolution that Xorg detects as valid.  For example on my system:

$ xrandr |grep 2560
HDMI-A-0 connected primary 2560x1440+1080+0 (normal left inverted right 
x axis y axis) 553mm x 311mm
    2560x1440     59.95*+
$

in my environment i do not populate xorg.conf with resolutions, rather I 
let X auto-detect them.  Then if the default resolution does not do what 
I want I have a script which sets the desired layout and resolution.  
For example here's one for my dual monitor setup:
$ cat ~/.screenlayout/duce.sh
#!/bin/sh
xrandr --output DisplayPort-0 --mode 1920x1080 --pos 0x0 --rotate right 
--output HDMI-A-0 --primary --mode 2560x1440 --pos 1080x0 --rotate 
normal --output DVI-D-0 --off
$

Regarding the nvidia utility setting the 2560x1600 resolution - perhaps 
its injecting custom modelines, if that is the case you can also do this 
via xrandr using the --newmode argument.

cheers,
-pete



-- 
Pete Wright
pete at nomadlogic.org
@nomadlogicLA