On Thu, 22 Jun 2000, Richard Henderson wrote:
> On Thu, Jun 22, 2000 at 09:41:58AM +0200, Geert Uytterhoeven wrote:
> > The problem is that drivers assume ISA memory space is at 0 and use e.g.
> >
> > request_mem_region(0xa0000, 65536)
> >
> > to request the legacy VGA region, while it should be
> >
> > request_mem_region(isa_mem_base+0xa0000, 65536)
> >
> > for compatibility with anything besides ia32.
>
> Well, yes and no. Again, what I'm saying is that one way
> to handle this is to *pretend* isa_mem_base==0, and that
> the entire ISA region is contiguous. Certainly that's good
> enough for region allocations. And if the damage is undone
> by ioremap, then the effect is not visible.
That works only if there's nothing else at address 0 that keeps the resource
busy.
> I'm not disagreeing that it would make sense to make this
> all a bit more explicit with proper interfaces. However,
> I don't see that happening any time real soon.
Hence my proposal for isa_request_mem_region(). It allows platform specific
code to take care of both the base address and the sparsity (if needed).
> > > What does your bus configuration look like?
> >
> > There are multiple legacy ISA regions on some PowerMacs, which
> > have multiple PCI buses and such.
>
> I guessed that. I was hoping to get specifics.
Benjamin Herrenschmidt <bh40@calva.net> can tell you more about it.
Gr{oetje,eeting}s,
Geert
-- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.orgIn personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds
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