Date: Fri, 22 Oct 2004 07:53:21 -0700
From: William Lee Irwin III <wli@holomorphy.com>
To: Matt Porter <mporter@kernel.crashing.org>
Cc: Glenn Burkhardt <glenn@aoi-industries.com>, linux-kernel@vger.kernel.org
Subject: Re: remap_page_range64() for PPC
Message-ID: <20041022145321.GV17038@holomorphy.com>
References: <20041016034642.F1DD0C60D@aoi-industries.com> <20041015233226.B1500@home.com>
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On Fri, Oct 15, 2004 at 11:46:42PM -0400, Glenn Burkhardt wrote:
>> I'm writing an application to run on a PowerPC with a 2.4 embedded
>> Linux kernel, and I want to make device registers for our custom
>> hardware accessable from user space with mmap().  The physical address
>> of the device is above the 4gb boundary (we attach to the 440's
>> external peripheral bus), so a standard 'remap_page_range()' call
>> won't work.

On Fri, Oct 15, 2004 at 11:32:26PM -0700, Matt Porter wrote:
> This has come up several times on the ppc lists (but since we still
> don't have archives back, nobody can search anyway). I dropped
> 2.4 and 2.5 patches in source.mvista.com:/pub/linuxppc/ a long
> time ago.  You just need to update your board-specific fixup routine
> in that version or just make a copy or remap_page_range() into your
> driver and use u64 for the phys address.
> The real fix, of course, is in the -mm tree as remap_pfn_range(),
> I plan to merge 440 io_remap_page_range() support on top of that
> call when it goes into mainline. But that doesn't help you with
> 2.4. :)

It has gone mainline. Glenn Burkhardt's troubles should now be fixed
for all time, unless io_remap_page_range() itself is in question. I'd
like to carry out a similar conversion on io_remap_page_range() so that
it can have similar safety against physical address overflow. There is
one 32-bit architecture where all IO memory is beyond the 4GB boundary,
and a number where at least some crucial portions of it are. This would
then decide how many arguments io_remap_page_range() takes. There are
some difficulties in this (particularly for the architecture[s] it
would benefit most) so I've been punting on this issue thus far.


-- wli
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