Driving two independent heads from X [was: Re: [Gllug] Multiple X servers]

[rich at annexia.org]

I went out and bought some second hand USB keyboards and mice to
experiment with this more.

Plugging two USB keyboards into a PC is interesting - both keyboards
are active. Pressing the capslock key on one keyboard, for instance,
lights up the capslock light on both. The keyboards act interchangably,
which isn't quite what I had in mind.

On to the graphics cards: I plugged in a PCI-based S3 card alongside
my GeForce4 (AGP-2).

Then I used an XF86Config-4 similar to this edited example:

Section "Device"
        Identifier      "NVidia GeForce 4 Ti"
        Driver          "nv"
        BusID           "PCI:1:0:0"
EndSection

Section "Device"
        Identifier      "S3"
        Driver          "s3"
        BusID           "PCI:2:0:0"
EndSection

Section "Monitor"
        # For Gateway 2000 Vivitron 1572:
        Identifier      "Gateway"
        HorizSync       31.5-64
        VertRefresh     50-120
        Option          "DPMS"
EndSection

Section "Monitor"
        # For Viglen Envy.15P
        Identifier      "Viglen"
        HorizSync       30-64
        VertRefresh     50-90
        Option          "DPMS"
EndSection

Section "Screen"
        Identifier      "Screen0"
        Device          "NVidia GeForce 4 Ti"
        Monitor         "Gateway"
	[ ... display subsection ... ]
EndSection

Section "Screen"
        Identifier      "Screen1"
        Device          "S3"
        Monitor         "Viglen"
	[ ... display subsection ... ]
EndSection

The question is really what to put in the "ServerLayout" section.
I successfully powered up each screen individually by using a
ServerLayout section like this:

Section "ServerLayout"
        Identifier      "Layout0"
        Screen          "Screen0"      # or "Screen1"
        InputDevice     "Generic Keyboard"
        InputDevice     "Configured Mouse"
EndSection

So I can run _two_ X servers and drive each screen separately with the
"-layout" option (I didn't actually try this, but this was the method
suggested by another poster, and apparently it works).

What I really want to do, however, is drive both heads from the
same X server, but still have them act separately so that, for instance,
two users can log in separately.

I couldn't come up with a ServerLayout section which managed this.
The closest is:

Section "ServerLayout"
        Identifier      "Layout0"
        Screen          0 "Screen0"
        Screen          1 "Screen1"
        InputDevice     "Generic Keyboard"
        InputDevice     "Configured Mouse"
EndSection

... but this actually crashes the X server solid at some point,
although it's not exactly clear why.

I'll experiment on this a bit more later anyhow.

Rich.

-- 
Richard Jones, Red Hat Inc. (London, UK) http://www.redhat.com/software/ccm
http://www.annexia.org/ Freshmeat projects: http://freshmeat.net/users/rwmj

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