Comment 39 for bug 806032

I don't know why you would get that error. Can you modprobe acpi-call and run:

c(){ echo "$1" | sudo tee /proc/acpi/call >/dev/null && sudo cat /proc/acpi/call;echo;}

c '\ASLB'
c '\_SB_.PCI0.GFX0.CAL1'

Please post the output of the last two commands (the first command just defines a helper function).
For me, the first one outputs 0xb378f018. In my DSDT, CAL1 is named "CADL" (though CALn with 2 <= n <= 8 has the same name as yours) and shows 0x100.

On my laptop, the CADL (CAD1) field appears as: /proc/iomem: b376f000-b379efff : ACPI Non-volatile Storage

Note that these initial scripts have been tested on an Oneiric machine (I cannot remember whether this was with the xorg-edgers/ppa repository enabled or not), later tests have been done on a vanilla kernel from kernel.org with a custom config.