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Re: working xorg.conf i promised

On Mon, Jun 04, 2007 at 10:55:42PM -0700, Brian Morris wrote:
> On 6/4/07, Eugen Paiuc <e.paiuc@gmail.com> wrote:
> on the other hand, my hand fixed xorg.conf *will* do 800x600 8 bit.
> it may do 640x480 16 bit too with a little more patience, I think.
> there is some issue about whatever mode you boot from too,
> there is trouble switching if you change your mind.

For some Mac video cards, we don't actually know how to change the
current resolution. This is why in general users are expected to just
stay with the settings they had before booting Linux.

> the other thing the other guys were discussing I guess was about that
> the FPU of '040 even when present is not complete as the '030 coprocessor
> (68881/2) was, so a few FPU functions are emulated still, but this is
> supposed to be handle by the kernel. I don't know what that
> business was about a bug in Xorg (i guess it can be looked up though).

There were a couple things being discussed. One was the fpsp040 code,
which is used on a full 68040 to emulate some of the extra instructions
that are implemented in hardware on the 68881 and 68882 but not in the
built-in FPU on the 68040. The other thing was the emulation of FPU
instructions on a 68LC040, which uses the full 68882 emulator that is
used with a 68020/68030 that does not have an FPU attached. The math-emu
code in the Linux kernel for this purpose is not complete, and it was
pointed out that X uses a couple instructions that aren't emulated
correctly in this code but should work in the fpsp040 code.

> when i tried on mine i did not realize that (appears) the framebuffer
> is named "MAC" (so kernel indicates choices of either that or "Valkyrie"
> which is correct for 630 but not for 650, but the name that the system
> provides is *not* "Mac" rather some obscure four letter acronym starting
> with "D"

The generic driver is "macfb" and will try to use whatever your main
display was before booting in whatever mode it was already in. The
four letter acronym you saw is DAFB, which is the name of the particular
hardware in the Q650 (among others). The macfb driver is similar to the
vesafb driver on the PC side in that it can provide a basic display, but
it doesn't always give you the full hardware capabilities. The only full
native driver we have for an m68k Mac is valkyrie (Q630) since this
hardware is also present in some PowerMac models. Writing better video
drivers is honestly not a high priority for most people involved, but
if you're interested in it there are people here who could provide advice.

	Brad Boyer

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