Re: X11 per machine_arch not per port (Was: Moving ports across to X11R7)

[Michael <macallan%netbsd.org@localhost>]

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Hello,

On Feb 8, 2009, at 2:27 PM, David Brownlee wrote:

> On Sun, 8 Feb 2009, Michael wrote:
>
> > On Feb 8, 2009, at 12:17 PM, David Brownlee wrote:
> >
> > > On Sun, 8 Feb 2009, Michael wrote:
> > > > Should work for the client stuff at least. The only  
> > > > incompatibility I can think of right now is the way we mmap (PCI)  
> > > > IO space on powerpc and shark - by picking a magic address range  
> > > > which isn't used by any PCI device, on macppc it's 0xf2000000  
> > > > ( traditionally the 1st PCI bridge's IO range ), prep and ofppc  
> > > > use different values, they're currently #defined in sys/params.h  
> > > > so there are no magic values or #ifdefs in the Xserver. We could  
> > > > just add an ioctl so the Xserver can ask the kernel where it  
> > > > would find IO space, that would take a few clock cycles more  
> > > > during setup but the result would be the same and Xservers would  
> > > > be compatible across $MACHINE_ARCH.
> > >
> > >         Is there any sense in adding it to the information exported by
> > >         /dev/fb? (I expect "no" is the answer here, but just checking).
> >
> > We don't need it on sparc(64) - all the Sun graphics boards I've  
> > seen so far either map no IO space or have all the registers  
> > accessible via memory space too. We need it on macppc and shark for  
> > chips like the C&T 65550 or IGS CyberPro where only the blitter is  
> > memory mapped and all the rest is in extended VGA registers.
>
>         Could it be potentially useful in the future for arbitrary PCI
>         boards on sparc64 and macppc? (Just curious)

Not really. Remember, this is for mmap()ing a graphics adapter through  
wsdisplay's ttys. The option to mmap the appropriate IO space was  
added so the Xserver wouldn't have to know or care about the  
underlying bus topology - many Macs can have more than one PCI domain  
for example. This way we just hand it the IO space that contains the  
device's IO registers.

> > >         Another option might be to provide it via a machdep sysctl value?
> >
> > I fail to see the advantage over an ioctl - it's not like this is a  
> > value which users should be able to change.
>
>         Its easier for users to determine what the value is, and that
>         there is such a machdep value for the current host. I would
>         have a slight preference for sysctl, but certainly not a strong
>         one.

What would they do with it unless they want to hack the Xserver? This  
value is certainly not useful to 'normal' users.

have fun
Michael

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