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Re: Proposal: non-PC ISA bus support

To: Richard Henderson <rth@twiddle.net>
Subject: Re: Proposal: non-PC ISA bus support
From: Geert Uytterhoeven <geert@linux-m68k.org>
Date: Thu, 22 Jun 2000 09:41:58 +0200 (MET DST)
Cc: Linux kernel <linux-kernel@vger.rutgers.edu>, Linux/PPC Development <linuxppc-dev@lists.linuxppc.org>, Linux/MIPS Development <linux@cthulhu.engr.sgi.com>
In-reply-to: <20000622001916.A29550@twiddle.net>
Sender: owner-linux-mips@oss.sgi.com
On Thu, 22 Jun 2000, Richard Henderson wrote:
> On Thu, Jun 22, 2000 at 08:45:47AM +0200, Geert Uytterhoeven wrote:
> > But with ioremap() you cannot specify where it has to be mapped, right? So
> > you're still stuck with an offset.
> 
> Huh?  Who cares where it's mapped.  "Some unused space."
> A pointer is a pointer.
> 
> In my case there is a direct correlation between the "base address"
> and the "ioremaped address" -- the addition of a constant.  That's
> the win for using 64-bit pointers.  ;-)

I think we're talking about something different. I don't care about the pointer
nor the ioremap() neither (we explicitly map it in MMU_init()).

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.

> > > the ISA bus is contained within exactly one PCI hose.
> > 
> > Which is not the case on some boxes :-(
> 
> The only machines I knew about that had this were the DEC NUMA
> machines.  What does your bus configuration look like?

There are multiple legacy ISA regions on some PowerMacs, which have multiple
PCI buses and such.

Gr{oetje,eeting}s,

                                                Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In 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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