monitor hotplug resolution switch

[Felix Miata]

Johann Obermayr composed on 2017-12-13 08:36 (UTC:

>> Johann Obermayr composed:

>>> i have a x86 machine with i915 graphics.

>>> With connected display (1920x1080) all is ok.

>>> But if I disconnect the monitor, the resolution switch to 320x200.

>>> How can I disable this ?

>>> I will always have the same resolution (1920x1080)

>>> How can I do this ?

>> some more info is certainly necessary

>> what OS?
>> what remaining monitor?

>> what do xrandr say?

> yes, sorry.
> X86 dualcore Intel(R) Celeron(R) CPU G1820 @ 2.70GHz
> With On board graphics i915

'inxi -c0 -G' and/or 'lspci -nnk | grep -A4 VGA' would tell a bit more.

> Older Yocto build with Kernel 3.10.0                            

That kernel version is older than your G1820 CPU.

> X.Org X Server 1.14.0
> Release Date: 2013-03-05
> [1274713.521] X Protocol Version 11, Revision 0
> [1274713.521] Build Operating System: Linux 3.2.0-126-generic-pae i686
> [1274713.521] Current Operating System: Linux sigmatek-x86-mp 3.10.0 #48 SMP PREEMPT Wed Dec 6 18:30:54 CET 2017 i686
> [1274713.521] Current version of pixman: 0.29.2                         

Why did you omit the "Kernel command line:" line? What's on it might explain why
falling back to 320x200, if the age of your hardware being newer than your
software does not.

> And using xf86-video-intel-2.21.3.tar.bz2                            

That predates the release of your G1820 (Haswell) CPU by nearly a year.

> xorg.conf
...
> Section "Screen"
> 	Identifier "Screen0"
> 	Monitor    "Monitor0"
> 	DefaultDepth 16
> 	SubSection "Display"
> 		Viewport   0 0
> 		Depth     16
> 	EndSubSection
> EndSection

> Yes we use 16 bit color depth.                   

That's not as well tested as the higher depths, and may cause inexplicable trouble.

> root at sigmatek-x86-mp:~# xrandr
> Screen 0: minimum 320 x 200, current 1920 x 1080, maximum 8192 x 8192
> VGA1 disconnected
> DP1 disconnected
> HDMI1 disconnected
> DP2 disconnected
> HDMI2 disconnected
> DP3 connected
>    1920x1080      60.0 +
> HDMI3 disconnected

> But after disconnect the monitor, the driver will change resolution to 320x200.
> But we will, that driver does not change the resolution. Or we can define the default resolution. 

Section "Monitor"
...
	Option		"PreferredMode"	"1920x1080"
...
EndSection

PreferredMode option should define resolution preferred, if the hardware is
supported.
-- 
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 Team OS/2 ** Reg. Linux User #211409 ** a11y rocks!

Felix Miata  ***  http://fm.no-ip.com/