linux-kernel - Re: [PATCH] iommu: Remove stub functions for !CONFIG_IOMMU

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Date:	Mon, 29 Aug 2011 14:25:16 +0200
From:	"Roedel, Joerg" <Joerg.Roedel@....com>
To:	Ohad Ben-Cohen <ohad@...ery.com>
CC:	"iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
	Stepan Moskovchenko <stepanm@...eaurora.org>,
	David Woodhouse <dwmw2@...radead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	David Brown <davidb@...eaurora.org>
Subject: Re: [PATCH] iommu: Remove stub functions for !CONFIG_IOMMU_API

On Mon, Aug 29, 2011 at 06:59:05AM -0400, Ohad Ben-Cohen wrote:
> On Mon, Aug 29, 2011 at 1:15 PM, Roedel, Joerg <Joerg.Roedel@....com> wrote:
> > Isn't the abstraction that the drivers use the dma-api? There should be
> > an implementation that doesn't require the iommu-api for such devices,
> > no?
> 
> Before we boot a remote processor device we often need to map it to
> some (specific) bus addresses (e.g. to allow the processor access to
> certain peripheral devices), and we're doing it directly with the
> IOMMU API.
> 
> Do you think this kind of functionality should be added to the DMA API as well ?
> 
> IIRC, it was suggested awhile ago but you supported using the IOMMU
> API directly in this case.

Right, when the system has an iommu then the iommu-api is the right
choice to do that. But how to you handle this on systems without an
iommu?

	Joerg


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