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	Mon, 18 Apr 2011 10:15:51 -0400
From: Arnd Bergmann <arnd@arndb.de>
To: Marek Szyprowski <m.szyprowski@samsung.com>
Subject: Re: [PATCH 4/7] v4l: videobuf2: add IOMMU based DMA memory allocator
Date: Mon, 18 Apr 2011 16:15:48 +0200
Cc: linux-arm-kernel@lists.infradead.org,
	linux-samsung-soc@vger.kernel.org, linux-media@vger.kernel.org,
	Kyungmin Park <kyungmin.park@samsung.com>,
	Andrzej Pietrasiwiecz <andrzej.p@samsung.com>,
	Sylwester Nawrocki <s.nawrocki@samsung.com>,
	Kukjin Kim <kgene.kim@samsung.com>
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On Monday 18 April 2011, Marek Szyprowski wrote:
> From: Andrzej Pietrasiewicz <andrzej.p@samsung.com>
> 
> This patch adds new videobuf2 memory allocator dedicated to devices that
> supports IOMMU DMA mappings. A device with IOMMU module and a driver
> with include/iommu.h compatible interface is required. This allocator
> aquires memory with standard alloc_page() call and doesn't suffer from
> memory fragmentation issues. The allocator support following page sizes:
> 4KiB, 64KiB, 1MiB and 16MiB to reduce iommu translation overhead.

My feeling is that this is not the right abstraction. Why can't you
just implement the regular dma-mapping.h interfaces for your IOMMU
so that the videobuf code can use the existing allocators?

	Arnd