Re: [PATCH 3/4 v5] iommu/fsl: Add iommu domain attributes required by fsl PAMU driver.

[Scott Wood <scottwood@freescale.com>]

On 12/03/2012 10:57:29 AM, Sethi Varun-B16395 wrote:
> 
> 
> > -----Original Message-----
> > From: iommu-bounces@lists.linux-foundation.org [mailto:iommu-
> > bounces@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; iommu@lists.linux-foundation.org;  
> Wood
> > Scott-B07421; linuxppc-dev@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.

-Scott