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Re: Proposal: non-PC ISA bus support

To: Geert Uytterhoeven <geert@linux-m68k.org>
Subject: Re: Proposal: non-PC ISA bus support
From: Richard Henderson <rth@twiddle.net>
Date: Thu, 22 Jun 2000 01:59:03 -0700
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: <Pine.GSO.4.10.10006220938260.27193-100000@dandelion.sonytel.be>
References: <20000622001916.A29550@twiddle.net> <Pine.GSO.4.10.10006220938260.27193-100000@dandelion.sonytel.be>
Sender: owner-linux-mips@oss.sgi.com
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.

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.

> > 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.


r~

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