> I was envisioning this being used before the kernel really messed with MMU
> too much.

Yeah...  Makes it a bit harder to debug sometimes, though...  ;-)

> I noticed that pmap_bootstrap thinks that a good way to calculate
> VRAM size is to use rowbytes * screen_height.

Actually, that's not a bad way to do it if you assume that the video
resolution isn't changing.  It would be nice to reliably know the real
size (etc).

> Great! Then it's really, more or less, a for loop!

Basically (using your outside value of 5M):

i=0;
while ((i < 5M) && !bad_baddr(vbase+i))
	i += 128k;
vsize = i;

#if DIAGNOSTIC
if (vsize == 5M) {
	printf("VRAM not sized properly");
}
#endif

-allen

-- 
              Allen Briggs - end killing - briggs@macbsd.com