i810 driver: scaling vs. centering non-native resolutions

[Neil Toronto]

The Windows drivers have the ability to set this, so I'd like to patch 
the driver. I've had some experience (back in the DOS days) making video 
BIOS calls and writing directly to I/O ports, so I'm pretty confident I 
could do it with the right documentation.

So does anybody know where I can find the documentation? Something like 
a video BIOS reference for the i810 chipset would be nice.

Besides being cool and flexible, it's also pretty important for running 
external output from widescreen laptops. The proper way to clone the 
screen (Option "Clone" "true" in the "Device" section of xorg.conf) 
doesn't clone video overlays, so you can't watch movies on an external 
CRT or projector. The other way, which clones the signal itself (Option 
"MonitorLayout" "NONE,CRT+LFP"), clones a native-resolution signal no 
matter what the screen resolution is set to - at least on my laptop, 
because it scales it to fit. 4:3 CRTs and projectors hate widescreen 
signals.

I assume that, if a 1024x768 screen is centered on my 1280x800 LCD, 
it'll send a 1024x768 signal to VGA out. Is that right?

Neil