Planning The upgrade

[<jam...@em...>]

I have lookd with interst at the many "how to pages" for setting up a dual 
headed system,a nd it seems tha tmost of them were last updated when Kernel 2.4 
and XFree86 were still the standard.
Currently I am using 2.6 with the ALSA patches, and X.org as my Xserver. and 
Would like to be able to upgrade my system while downgrading as little software 
as possible.
The most promising tutorial I have found at 

http://cambuca.ldhs.cetuc.puc-rio.br/multiuser/

include the following section.
-Proper kernel 2.6 support
-Aivils Stoss notified me that multiple keyboards are possible without any kind 
of 2.6 kernel patching (see above). The trick is to request exclusive access to 
the event device, so that keyboard handler would not receive any event. This 
requires only small changes to the XFree86 patch (actually x.org fork as i 
expect the old XFree86 to die silently with their new license...). Aivils 
explains:

data[0]=1;
if (ioctl(fd, EVIOCGRAB, data) == 0)
printf("exclusive access granted");

"where fd is file descriptor of /dev/input/eventXX. I dont know wherethat is 
documented.

If You will highly polish Your solution, then take a look into Debian testing 
distro: Debian testing xf86 already includes 2.6.XX event device support.

Please check out this patch against xf86 4.3.0: 
http://ftp.debian.org/debian/pool/main/x/xfree86/xfree86_4.3.0-7.diff.gz (grep 
evdev). You can find this link via www.debian.org. Unfortunately i do not know 
how to works Debian. I know only some linux-ruby testersuse this event 
interface. xf86 event interface means usage of /dev/input/eventXX instead 
standard /dev/ttyXX for keyboard and /dev/input/mouseXX for mouse.If You will 
run multiple local Debian xf86 You should applay manualy Your own "TTY 
dependency remove" patch and seems add EVIOCGRAB to disable 2nd, 3rd ... 
keyboard presence on TTY and "xf86 PCI interference remove" patch.

Advantage: kernel remain unpatched. You can use two PS/2 keyboards under 
2.6.XX." 

With All of the talk of Ruby kernel patches, this almost seems too good to be 
true...and I don't really understand where to place those lines in the patch 
either(I am learning linux as quickly as oppurtunity permits).
I haven't begun yet on seting up my system, or even purchasing additional 
components until I get my homework done on the software.
It would also seem, with two monitors windows could easily be setup as a 
xinerama system.  X.org is easily configured likewise (it is part most of the 
installation tutorials I have read).  How simple can the switch be made 
from "xinerama" to "dual-head" mode?  Has Hot switching (commendering the other 
monitor while others are logged off, and being able to relinquish it to allow 
others to log on) been explored yet?

BTW, MY system specs,
Xeon 2.8 Ghz Intel, 300 GBhd, 256MB ram, intergrated intel Mother/Video/Sound 
Board, Lots of Open PCI slots, dual booting XP and ArchLinux.