How do I use kscreen?

Felix Miata mrmazda at
Thu Nov 6 09:27:54 GMT 2014

Duncan composed on 2014-11-06 08:42 (UTC):

> Note that it says first *DETAILED* timing is preferred.  The established 
> and standard timings are compatibility/legacy timings.  It's the first 
> DETAILED timing that's preferred, and as you can see here, that's 
> 1920x1080 (the h_active and v_active numbers) for this LG TV.  The dot-
> clock (aka PixClock) for that timing is 148.5 MHz.

> If your xorg log EDID has a preferred (likely first DETAILED) timing/
> resolution of 1024x768 and you're definitely using a native 1920x1080 
> full-HD monitor, then very likely that monitor EDID is defective and 
> reporting the wrong thing.

Nikos Chantziaras posted 2014-11-03 13:02:43:

"I upgraded my KDE installation to 4.11.13/4.14.2. I am now no longer
able to configure my monitor through KDE System Settings..."

Note keywords "upgraded" and "no longer".

> If OTOH, the EDID in xorg is saying 1920x1080 is preferred, then it's 
> gotta be the drivers screwing things up, tho at this point I'm pretty 
> sure it's going to be the monitor and the driver is simply a reporter of 
> the facts as it collects them, caught in the crossfire.

Not likely the upgrade process broke the display's EDID.

Note in the large size of his display:
EDID Info:
        Name:  "SyncMaster"
        Width:  51
        Height:  29

If those are correct, that's somewhere around a 55" screen, which at
1920x1080 is a pixel density under 40. Maybe that's the root of the problem,
some sort of driver sanity check failing and blacklisting the higher
resolution mode getting through the automagic process.

OTOH, earlier in that output is reported "MMSize: QSize(510, 290)", which is
a 23 inch 96 DPI screen. That in a way maybe is saying the EDID is broken,
maybe in a way that the older version/driver handled but the newer won't. I
can't tell without the whole Xorg.0.log. I'm guessing that 510,290 report may
be there because of normal X behavior when not overridden, forcing DPI to 96,
disregarding the actual display dimensions.

If that hardware was here for troubleshooting, I'd second[1] disable kscreen,
then either configure an xorg.conf or a suite of settings in xorg.conf.d/, or
try an X startup script forcing the desired settings using xrandr, similar to

	# xrandr --output DVI-D-0 --mode 1920x1080

> ...various modeline generators to generate custom resolution modelines...

I've never post-XFree86 found it necessary to include a modeline in a config
file to get any display, with or without valid EDID, to use its
native/preferred mode, or any other supported mode. Given the parameters one
would feed a generator (desired mode, HorizSync range, VertRefresh range),
Xorg does what a generator does automatically, and for me, always satisfactorily.

[1] first thing I'd do is uninstall NVidia. I only ever use FOSS drivers.
"The wise are known for their understanding, and pleasant
words are persuasive." Proverbs 16:21 (New Living Translation)

 Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata  ***
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