On Tue, Oct 14, 2014 at 01:53:59PM +0100, Laurent Pinchart wrote: > Hi Will,
Hi Laurent, > On Monday 22 September 2014 18:50:27 Will Deacon wrote: > > On Mon, Sep 22, 2014 at 10:29:10AM +0100, Thierry Reding wrote: > > > Agreed. I wonder how useful it is to know the set of IOMMU instances > > > that each device can master through. Wouldn't it be more useful to keep > > > a list of master interfaces for each device? The set of IOMMU instances > > > can trivially be derived from that. > > > > I'm struggling to think how that would look. What do you mean by `master > > interfaces' in terms of the code we have in Linux? At the end of the day, > > the list of IOMMU instances (i.e. iommu_dma_mapping) exists because you > > and Laurent have use-cases involving devices mastering through multiple > > IOMMUs. If it doesn't work for you, it might be best for you to send me > > the patch ;) > > Just for the record, I've brought up the topic of masters being served by > multiple IOMMUs, but don't have a use case for it (yet at least). I do have > masters served through multiple streams with separate stream IDs, but all by > the same IOMMU. Ok. I spoke to Arnd, David and Joerg at LPC and the consensus was that the DMA-mapping API should *not* be exposed to the details of masters that master through multiple IOMMUs. Instead, that should be abstracted by the device API by exposing that device as a single struct device. So, that's certainly an area that needs more work and I'll drop the limited support I'd cooked up from this patch set in the next version. Will _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
