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Date: Thu, 24 Nov 2011 16:27:47 +0100
From: "'Joerg Roedel'" <Joerg.Roedel@amd.com>
To: Marek Szyprowski <m.szyprowski@samsung.com>
CC: "'David Woodhouse'" <dwmw2@infradead.org>,
        "'Ohad Ben-Cohen'" <ohad@wizery.com>,
        "'KyongHo Cho'" <pullip.cho@samsung.com>,
        "'Kai Huang'" <mail.kai.huang@gmail.com>, <kvm@vger.kernel.org>,
        "'Arnd Bergmann'" <arnd@arndb.de>, <linux-kernel@vger.kernel.org>,
        <iommu@lists.linux-foundation.org>,
        "'Laurent Pinchart'" <laurent.pinchart@ideasonboard.com>,
        "'David Brown'" <davidb@codeaurora.org>, <linux-omap@vger.kernel.org>,
        "'Stepan Moskovchenko'" <stepanm@codeaurora.org>,
        <linux-arm-kernel@lists.infradead.org>
Subject: Re: Changing IOMMU-API for generic DMA-mapping supported by the
 hardware
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On Thu, Nov 24, 2011 at 01:52:33PM +0100, Marek Szyprowski wrote:
> In my DMA-mapping IOMMU integration I've used a dma_iommu_mapping structure,
> which contains a pointer to iommu domain, a bitmap and a lock. Maybe we 
> should consider extending iommu domain with allocation bitmap (or other 
> structure that hold information about used/unused iova ranges)? From the
> DMA-mapping (as a IOMMU client) perspective we only need 2 more callbacks
> in IOMMU API: alloc_iova_range() and free_iova_range(). 
> 
> Each IOMMU implementation can provide these calls based on internal bitmap
> allocator which will also cover the issue with reserved ranges. What do you
> think about such solution?

Hmm, the main point of a generic DMA-mapping implementation is that a
common address-allocator will be used. Today every IOMMU driver that
implements the DMA-API has its own allocator, this is something to unify
between for all drivers.

The allocator information can be stored in the default iommu_domain. We
need a user-private pointer there, but that is easy to add.


	Joerg

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