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From: Arnd Bergmann <arnd@arndb.de>
To: David Rientjes <rientjes@google.com>
Subject: Re: [patch 4/4] x86: allow CONFIG_ISA_DMA_API to be disabled
Date: Thu, 27 Jan 2011 09:23:37 +0100
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Cc: Andrew Morton <akpm@linux-foundation.org>, Ingo Molnar <mingo@redhat.com>,
        "H. Peter Anvin" <hpa@zytor.com>, Thomas Gleixner <tglx@linutronix.de>,
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On Thursday 27 January 2011 04:14:54 David Rientjes wrote:
> 
> Not all 64-bit systems require ISA-style DMA, so allow it to be
> configurable.  x86 utilizes the generic ISA DMA allocator from
> kernel/dma.c, so require it only when CONFIG_ISA_DMA_API is enabled.
> 
> Disabling CONFIG_ISA_DMA_API is dependent on x86_64 since those machines
> do not have ISA slots and benefit the most from disabling the option (and
> on CONFIG_EXPERT as required by H. Peter Anvin).

But the x86_64 machines can also run 32 bit kernel, and I would expect
that they don't need ISA DMA in that configuration either.

I think it would make sense to let the CONFIG_EXPERT user disable
DMA for 32 bit as well.

	Arnd