kms howto - is there one?

Adam Jackson ajax at
Fri Mar 19 18:01:07 UTC 2010

On Wed, 2010-03-17 at 18:48 -0400, Felix Miata wrote:

> # xrandr --output VGA1 --mode 1600x1200
> xrandr: cannot find mode 1600x1200

Which means there's not a 1600x1200 mode listed on that output.

> # xrandr --addmode UXGA 1600x1200
> xrandr: cannot find output "UXGA"

This attempts to add a mode named "1600x1200" to an output named UXGA.
You have no such output.

> # xrandr --addmode VGA1 1600x1200
> xrandr: cannot find mode "1600x1200"

Modes don't exist a priori.  Create the mode you want and then add it to
the appropriate output.

% gtf 1600 1200 60 | grep Mode
  Modeline "1600x1200_60.00"  160.96  1600 1704 1880 2160  1200 1201 1204 1242  -HSync +Vsync
% xrandr --newmode 1600x1200 $(gtf 1600 1200 60 | grep Mode | read a b c; echo $c)
% xrandr --addmode VGA1 1600x1200

Note that mode names have no semantic meaning.  They're just strings.

Use gtf(1) to generate mode timings for CRTs, and cvt(1) for LCDs.

- ajax
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