> -----Original Message----- > From: Wood Scott-B07421 > Sent: Monday, December 03, 2012 10:34 PM > To: Sethi Varun-B16395 > Cc: Joerg Roedel; linux-kernel@vger.kernel.org; iommu@lists.linux- > foundation.org; Wood Scott-B07421; linuxppc-...@lists.ozlabs.org; Tabi > Timur-B04825 > Subject: Re: [PATCH 3/4 v5] iommu/fsl: Add iommu domain attributes > required by fsl PAMU driver. > > On 12/03/2012 10:57:29 AM, Sethi Varun-B16395 wrote: > > > > > > > -----Original Message----- > > > From: iommu-boun...@lists.linux-foundation.org [mailto:iommu- > > > boun...@lists.linux-foundation.org] On Behalf Of Joerg Roedel > > > Sent: Sunday, December 02, 2012 7:33 PM > > > To: Sethi Varun-B16395 > > > Cc: linux-kernel@vger.kernel.org; io...@lists.linux-foundation.org; > > Wood > > > Scott-B07421; linuxppc-...@lists.ozlabs.org; Tabi Timur-B04825 > > > Subject: Re: [PATCH 3/4 v5] iommu/fsl: Add iommu domain attributes > > > required by fsl PAMU driver. > > > > > > Hmm, we need to work out a good abstraction for this. > > > > > > On Tue, Nov 20, 2012 at 07:24:56PM +0530, Varun Sethi wrote: > > > > Added the following domain attributes required by FSL PAMU driver: > > > > 1. Subwindows field added to the iommu domain geometry attribute. > > > > > > Are the Subwindows mapped with full size or do you map only parts > > of the > > > subwindows? > > > > > [Sethi Varun-B16395] It's possible to map a part of the subwindow i.e. > > size of the mapping can be less than the sub window size. > > > > > > + * This attribute indicates number of DMA subwindows > supported > > by > > > > + * the geometry. If there is a single window that maps the > > entire > > > > + * geometry, attribute must be set to "1". A value of "0" > > implies > > > > + * that this mechanism is not used at all(normal paging is > > used). > > > > + * Value other than* "0" or "1" indicates the actual number > of > > > > + * subwindows. > > > > + */ > > > > > > This semantic is ugly, how about a feature detection mechanism? > > > > > [Sethi Varun-B16395] A feature mechanism to query the type of IOMMU? > > A feature mechanism to determine whether this subwindow mechanism is > available, and what the limits are. > So, we use the IOMMU capability interface to find out if IOMMU supports sub windows or not, right? But still number of sub windows would be specified as a part of the geometry and the valid value for sub windows would 0,1 or actual number of sub windows.
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