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RE: Monitor detection failure and video display



----Original Message----
From: Camaleón [mailto:noelamac@gmail.com]
Sent: Friday, October 08, 2010 9:23 AM
To: debian-user@lists.debian.org
Subject: Re: Monitor detection failure and video display

> On Thu, 07 Oct 2010 11:58:51 -0800, James Zuelow wrote:
> 
>> Some additional info.
>> 
>> I tried this:
>> 
>> Section "Device"
>>     Identifier     "Device0"
>>     Driver         "nouveau"
>>     Option         "IgnoreEDID" "true"
>> EndSection
>> 
>> But I get this in /var/log/Xorg.0.log (actually I get that error if
>> the IgnoreEDID is there or not):
> 
> Mmm, I don't think that should be the proper way to handle that
> (unless you know for sure that EDID information is completey broken
> with your monitor and you are then forced to disabled it).

No, you're right.  I was way off, thinking it was xorg failing to get EDID info from a monitor that was causing the video to go blank.

I was just playing with this and it turns out it was pretty simple.

With the new 2.6.32 kernel in Squeeze, KMS is turned on.  KMS attempts to autodetect a monitor, and if it doesn't find one video goes blank.  The way around this is to override KMS with the video= boot parameter.

So I modified /etc/default/grub and changed the boot options from "quiet" to "quiet video=VGA-1:e"

The "video=VGA-1:e" tells the kernel to enable VGA-1 regardless of what it sees.  Then xorg will start.  It still won't get EDID info if the monitor is powered off, but I can set a specific mode for the monitor which seems to work.

I have an image I use for kiosks, so after applying the image to a computer I have to tweak the video= kernel option for each one, but that's not really an issue as I have to tweak the xorg.conf mode setting for each monitor anyway.  It is just a matter of figuring out which video setting to use, VGA-1 for the VGA ports, or DVI-I-1 for a DVI port.  I can't find the code for an S-Video output, which is really handy for display kiosks using a large screen TV as a display unit (especially cause you can push an s-video signal over a 50 or 100 foot cable).

If I wanted to, I could set the display setting in the kernel command line as in "video=VGA-1:1920x1080@52e"  This would set the display to 1920x1080 at 52Hz refresh.  I might need to do that with some of the bigscreen TV's, and probably have to do that for anything going over the S-video port if the xorg.conf modeline doesn't work for some reason.

Anyway, it is working now, and this should be enough info to get people going on a Google search if they're in the same boat.


James Z

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