RE: [PATCH 3/4 v5] iommu/fsl: Add iommu domain attributes requiredby fsl PAMU driver.

[Sethi Varun-B16395]

> -----Original Message-----
> From: iommu-bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx [mailto:iommu-
> bounces@xxxxxxxxxxxxxxxxxxxxxxxxxx] On Behalf Of Joerg Roedel
> Sent: Sunday, December 02, 2012 7:33 PM
> To: Sethi Varun-B16395
> Cc: linux-kernel@xxxxxxxxxxxxxxx; iommu@xxxxxxxxxxxxxxxxxxxxxxxxxx; Wood
> Scott-B07421; linuxppc-dev@xxxxxxxxxxxxxxxx; 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?

-Varun

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