From mboxrd@z Thu Jan  1 00:00:00 1970
From: "jroedel-l3A5Bk7waGM@public.gmane.org" <jroedel-l3A5Bk7waGM@public.gmane.org>
Subject: Re: [RFC PATCH v3 5/7] dma-mapping: detect and configure IOMMU in
	of_dma_configure
Date: Mon, 27 Oct 2014 17:33:57 +0100
Message-ID: <20141027163357.GF9734@suse.de>
References: <1410539695-29128-1-git-send-email-will.deacon@arm.com>
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To: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>
Cc: "arnd-r2nGTMty4D4@public.gmane.org" <arnd-r2nGTMty4D4@public.gmane.org>, "iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org" <iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>, Thierry Reding <thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Laurent Pinchart <laurent.pinchart-ryLnwIuWjnjg/C1BVhZhaw@public.gmane.org>, "Varun.Sethi-KZfg59tc24xl57MIdRCFDg@public.gmane.org" <Varun.Sethi-KZfg59tc24xl57MIdRCFDg@public.gmane.org>, "dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org" <dwmw2-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>, "linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org" <linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org>
List-Id: iommu@lists.linux-foundation.org

On Mon, Oct 27, 2014 at 04:02:16PM +0000, Will Deacon wrote:
> On Mon, Oct 27, 2014 at 11:30:33AM +0000, Laurent Pinchart wrote:
> > I'm not sure to follow you here. Aren't we already exposing masters that 
> > master through multiple IOMMUs as single instances of struct device ?
> 
> Hmm, yes, now you've confused me too! The conclusion was certainly that
> dma-mapping should not be the one dealing with the I/O topology. Domain
> allocation would then be an iommu callback (something like
> ->get_default_domain), but the rest of the details weren't fleshed out.

The idea is that the IOMMU core code will allocate a default domain for
each iommu-group at initialization time. This domain can be requested
later by a new iommu-api function and used for DMA-API mappings.

A device still can be assigned to another domain by driver code (like
VFIO). But if the device is later de-assigned the IOMMU core-code
automatically puts it back into the default domain.


	Joerg