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Old 11-06-07, 12:12 PM   #1
CptDondo
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Default Linux, xorg, and dual head, problems with vga arbitration in xorg1.3

I also posted this on forums.nvidia.com; sorry for the crosstalk if you're seeing this twice.

I'm trying to set up a dual-head system. I am running into a problem where only 1 screen is active at a time.

The current system has 2 heads; when X starts I can see the first server start up. As soon as the second server starts up, the first one goes black.

X is running on both heads; just the screen is black.

root 7832 0.3 0.5 65476 11996 ? SLs 21:10 0:01 /usr/X11R6/bin/X :0 -audit 0 -layout Yan -novtswitch -sharevts vt7 -auth /var/lib/gdm/:0.Xauth -nolisten tcp
root 7867 7.6 1.0 75820 21764 ? RLs 21:10 0:27 /usr/X11R6/bin/X :1 -audit 0 -layout Noriko -novtswitch -sharevts vt7 -auth /var/lib/gdm/:1.Xauth -nolisten tcp

There is nothing to indicate that there is any problem.

I am using the latest binary nvidia driver but I have also confirmed this with older, known good versions of the nvidia driver. I am using the most recent version of the nvidia binary module:

NVIDIA GLX Module 100.14.19 Wed Sep 12 14:51:24 PDT 2007

The system has one Quadro PCI card and one GeForce7600 PCIe 16x card.

01:06.0 VGA compatible controller: nVidia Corporation NV34GL [Quadro NVS 280 PCI] (rev a1)
05:00.0 VGA compatible controller: nVidia Corporation G70 [GeForce 7600 GT] (rev a1)

I am stumped. I've set this up in the past without these problems.... At this point the only thing I can think of is that the GT7600 card I am using simply is not compatible with dual head....

I posted this on the xorg list and received the following reply:



This is issue totally related with the VGA arbitration [0] which we discussed some days ago here. No one knows if the nvidia driver will only use MMIO and no legacy stuff to decode the resources.

[0] http://lists.freedesktop.org/archive...er/029685.html



Can someone at nVidia shed some light on this?

--Yan
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Old 11-06-07, 01:28 PM   #2
AaronP
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Default Re: Linux, xorg, and dual head, problems with vga arbitration in xorg1.3

Hi CptDondo,
I'm afraid the nvidia driver doesn't really support so-called "multiseat" configurations. If it worked in the past, it was by luck.
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Old 11-06-07, 01:33 PM   #3
CptDondo
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Default Re: Linux, xorg, and dual head, problems with vga arbitration in xorg1.3

Too bad. That's a pretty essential functionality for me. :-(

It's also pretty useful for things like Mythv.... In the past, it's worked wonderfully, even if accidentally.

Any chance of this being supported in the future? Any way to file a feature request?
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Old 11-06-07, 04:10 PM   #4
AaronP
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Default Re: Linux, xorg, and dual head, problems with vga arbitration in xorg1.3

There are currently no plans to officially support it, but knowing how many users want a particular feature helps us prioritize future development.

As for MythTV, why isn't a single server with multiple X screens sufficient?
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Old 11-06-07, 04:21 PM   #5
CptDondo
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Default Re: Linux, xorg, and dual head, problems with vga arbitration in xorg1.3

AFAIK, For Myth, only the first head is accelerated unless both are used as "twinview". Also, I like to have myth logged in as its own user with limited priveledges.

So with 2 cards, you can have 2 accelerated heads, each with its own X session. One used to show stuff, the other to work on, edit movies, etc. It works really well for some of us.

Maybe there is a way to do that within the nvidia driver framework. All I really want is 2 users logged in with 2 keyboards and 2 mice and 2 monitors.

--Yan
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Old 03-07-08, 02:44 PM   #6
DeFKnoL
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Default Re: Linux, xorg, and dual head, problems with vga arbitration in xorg1.3

I am trying to do this too - and I am seeing the same problem. So just to throw in the fact that there are multiple people out there who want this.
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Old 03-07-08, 03:46 PM   #7
AaronP
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Default Re: Linux, xorg, and dual head, problems with vga arbitration in xorg1.3

@CptDondo,

I'm not sure what you mean by "only the first head is accelerated unless both are used as 'twinview'." The NVIDIA driver fully accelerates both heads when used in a dual X screen configuration.

@DeFKnoL,

There are currently known problems in the X server with the way it deals with multiple devices. There is talk of allowing X drivers being able to completely disable the X server's VGA arbitration logic, which should help improve multiple card configurations. As I mentioned before, multiseat configurations are still unsupported but knowing how many people want them helps us prioritize future development.
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Old 07-28-08, 11:28 PM   #8
andersja
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Lightbulb Re: Linux, xorg, and dual head, problems with vga arbitration in xorg1.3

@AaronP & others: I'm trying to achieve the same. Reported a bug at https://bugs.launchpad.net/ubuntu/+s...r/+bug/251803/

There is a big trend toward using linux computers as multiseat devices. See for example http://linuxgazette.net/124/smith.html and http://netpatia.blogspot.com/2008/02...buntu-804.html

Would be a big sell for nVidia if this became supported!
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Old 10-16-08, 10:32 AM   #9
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Default Re: Linux, xorg, and dual head, problems with vga arbitration in xorg1.3

Quote:
Originally Posted by AaronP View Post
Hi CptDondo,
I'm afraid the nvidia driver doesn't really support so-called "multiseat" configurations. If it worked in the past, it was by luck.
Multiseat worked up to 169.12, but does not on 173.x and 177.80.

Will NVidia work on a solutions which integrates with the work described under http://wiki.x.org/wiki/VgaArbiter ?

NVidia has their own kernel module anyways, but it would be nice if the stock X server could use the same interface for all drivers to do the initializations stuff and so on.
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