Hi,

Well, what I meant by not working is that I'm putting "options 
OFB_FAKE_VGA_FB" in the kernel configuration file. The kernel compiles and 
is able to be booted. However, attempting to start X still gives the 
infamous "xf86MapVidMem: could not mmap screen [s=20000,a=a0000] (Invalid 
argument)" message. I guess I'll just run this thing headless for now 
since I have too many computers and not enough monitors.

Regards,
John

On Fri, 10 Nov 2006, Michael Lorenz wrote:

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> Hello,
>
> On Nov 10, 2006, at 10:57, John wrote:
>
>> Haven't been able to get OFB_FAKE_VGA_FB to work. Is this only in the 
>> -current kernel? Or does it also depend on something else in the kernel 
>> configuration? Also, while perusing the mail archives I came upon this 
>> post: http://mail-index.netbsd.org/port-macppc/2004/03/09/0004.html
>
> It is an old enough hack to be in 3.0. Originally intended for ofb only but 
> most other wsdisplay drivers respect it ( machfb, chipsfb, voodoofb and 
> radeonfb do )
> And what exactly did you do? "Haven't been able to get <whatever> to work" is 
> not a useful problem description.
>
>> Basically, /xc/programs/Xserver/hw/xfree86/os-support/bsd/ppc_video.c was 
>> patched instead. I haven't tried it out yet though.
>
> Don't bother, this patch is dangerous.
> The problem is that many X drivers want to mmap the legacy VGA framebuffer at 
> 0xa0000 which is pointless on a mac since it isn't used for anything. The 
> patch allows you to mmap whatever is on physical address 0xa0000 which could 
> be anything but certainly nothing VGA-related even if your VGA board has the 
> legacy fb mapping enabled - anything below 0x80000000 on a mac is RAM, PCI 
> memory can only be accessed from 0x8000000 and above so you'd be messing 
> around in system memory instead.
> OFB_FAKE_VGA_FB is a little more sane - it redirects attempts to mmap(0xa0000 
> - 0xbffff) to the beginning of the actual framebuffer.
> The reason why X is doing that is to save and restore VGA textmode 
> information which is useless on macppc since nobody uses VGA textmode, the 
> right thing to do would be to disable this code in X. Some drivers ( like 
> atimisc ) do it, others don't.
>
> have fun
> Michael
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