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From: Keith Packard <>
To: Ingo Molnar <>
Cc:, Eric Anholt <>,
Subject: Re: [PATCH] Add io-mapping functions to dynamically map large device apertures
Date: Fri, 31 Oct 2008 09:59:29 -0700	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

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On Fri, 2008-10-31 at 10:21 +0100, Ingo Molnar wrote:

> it's ugly and inflexible to put x86 dependencies into generic headers. 
> (even though with a high likelyhood 32-bit x86 will be the only arch 
> to ever implement the iomap_atomic() APIs)
> Instead please add a HAVE_ATOMIC_IOMAP define to arch/x86/Kconfig:
>          def_bool y
>          depends on X86_32
> ... and use #ifndef HAVE_ATOMIC_IOMAP in include/linux/io-mapping.h 
> instead of #ifdef CONFIG_X86_64.

Just to clarify the issue here: there are two separate implementations
of the io_mapping API -- one for 'large address space' machines where
ioremap_wc can handle the typical graphics aperture within the kernel
virtual map, and the other using iomap_atomic_prot_pfn for machines with
puny address spaces.

All large address space machines can provide the io_mapping API without
any archtecture-specific support. For efficient 32-bit io_mapping
support, we require the new iomap_atomic_prot_pfn function.

So, it seems like what I want to do is use the large address space code
on any machine which supports it, and then use the iomap_atomic_prot_pfn
version for small address space machines which have the
iomap_atomic_prot_pfn function.

What I think you're suggesting is to just assume that machines without
iomap_atomic_prot_pfn have address spaces large enough to support the
ioremap_wc path. The alternative is to create a third (slow) path (which
I did before the iomap_atomic_prot_pfn API was introduced) that uses
ioremap_wc at run time for small address space machines without

Let me know which you'd prefer and I'll get a patch out ASAP.


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  reply	other threads:[~2008-10-31 16:59 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <>
2008-10-31  2:38 ` Eric Anholt
2008-10-31  2:38   ` [PATCH] i915: Use io-mapping interfaces instead of a variety of mapping kludges Eric Anholt
2008-10-31  9:21   ` [PATCH] Add io-mapping functions to dynamically map large device apertures Ingo Molnar
2008-10-31 16:59     ` Keith Packard [this message]
2008-11-03  8:37       ` Ingo Molnar
2008-11-03 17:09 [PATCH] [x86_32] Add io_map_atomic using fixmaps Keith Packard
2008-11-03 17:09 ` [PATCH] Add io-mapping functions to dynamically map large device apertures Keith Packard
  -- strict thread matches above, loose matches on Subject: below --
2008-10-22  9:36 io resources and cached mappings (was: [git pull] drm patches for 2.6.27-rc1) Ingo Molnar
2008-10-23  7:14 ` Keith Packard
2008-10-23  7:14   ` [PATCH] Add io-mapping functions to dynamically map large device apertures Keith Packard
2008-10-24  4:49     ` Randy Dunlap
2008-10-24  6:26       ` Keith Packard

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