Booting netbsd-GENERIC_MD on iMac G3 using ofwboot.xcf + genfb woes

[Sam van Kampen <sam+netbsd%tehsvk.net@localhost>]

Hi all,

I am attempting to boot the netbsd-GENERIC_MD kernel on an iMac G3
using ofwboot.xcf, however, when trying to boot it using the standard
ofwboot.xcf I get an error complaining that the bootloader could not
CLAIM the required amount of physical memory at 0x100000 for the
kernel image. This seems to be because the kernel image has grown
quite large, and is currently over 14MB in size. ofwboot.xcf is
configured with RELOC=0xE00000, so OFW loads it at 0xE00000 (=14MB).
The kernel expects to be loaded at 0x100000 (=1MB), but of course if
it is 14MB in size it starts to overlap with ofwboot. I've built a
custom ofwboot with RELOC=0x1000000 (=16MB) and that seems to leave
enough room for the kernel image.

I am not sure what the best way forward is here. We can bump RELOC, I
imagine, but that would exclude systems with <=16MB of memory, and
there are lots of kernel configurations which are small enough to
boot. Perhaps that is acceptable (I imagine there are very few macppc
systems that are useful _and_ that low on memory), or otherwise the
GENERIC_MD kernel can be shrunk a bit?

With one hurdle cleared I am now running into another: the kernel
starts, but when the framebuffer driver is loaded, the screen goes
completely blank.The last line I see is

    genfb0 at pci0 dev 16 function 0: ATI Technologies Rage 128 VR AGP
2x (rev. 0x00))

I see there are also some other framebuffer drivers which might work
(r128fb?) so I may try disabling genfb, and of course I will compile
with debug logging enabled and see if that gets me anywhere, but I
thought I'd drop it here as well in case anybody has any thoughts.

Cheers,

Sam