Re: Switching to Xorg

[Michael Lorenz <macallan%NetBSD.org@localhost>]

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Hello,

On Apr 7, 2008, at 18:03, der Mouse wrote:
> > If X wants to access a PCI graphics board it currently needs to be
> > the console. Part of the reason is that - unlike many 32bit machines
> > - PCI bus addresses don't coincide with their physical addresses from
> > the CPU's point of view, the console driver hides that from the
> > Xserver so it can mmap PCI resources with their bus addresses, but
> > only for the console.
>
> Surely the right thing to do is to fix the framebuffer drivers so mmap
> works on them without their having to be console?

No, the fb drivers need no fixing. The right thing to do is to fix X  
to look at more than one wsdisplay. Looking at the code first helps.

> > Also, the physical address of the PCI address space depends on the
> > machine and to make things more complicated some Ultras have more
> > than one PCI bus.
>
> None of which should matter; that's what the framebuffer driver is  
> for:
> to present a uniform interface to application code, regardless of the
> underlying resources.

Exactly, that's why X doesn't know or care about any of this.

> > Before you ask - none of this is different with Xorg, it may change
> > with their next major release if someone ports libpciaccess to
> > NetBSD.
>
> Better would be to fix the (severley) broken paradigm that has the X
> server knowing anything about buses.

Agreed, the Xserver trying to play operating system and messing with  
BARs and such is an abomination that needs to go away.

> The X server should be using a uniform interface presented by the  
> framebuffer driver, independent of the underlying bus(s) (if any) -  
> that's what drivers are *for*!  (It works fine that way on  
> sparc32....)

Not with PCI framebuffers and that's what we're talking about here.

have fun
Michael

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