On Mon, Jan 26, 2015 at 11:00:59AM +0000, Joerg Roedel wrote: > On Sun, Jan 25, 2015 at 05:38:22PM +0200, Laurent Pinchart wrote: > > IOMMU groups still seem a bit unclear to me. Will Deacon has nicely > > explained > > what they represent in > > http://lists.infradead.org/pipermail/linux-arm-kernel/2014-December/310816.html. > > The IOMMU core doesn't make groups > > mandatory, but requires them in some code paths. > > > > For example the coldplug device add function add_iommu_group() called for > > all > > devices already registered when bus_set_iommu() is called will try to warn > > of > > devices added multiple times with a WARN_ON(dev->iommu_group). Another > > example > > is the iommu_bus_notifier() function which will call the remove_device() > > operation only when dev->iommu_group isn't NULL. > > > > I'm thus unsure whether groups should be made mandatory, or whether the > > IOMMU > > core should be fixed to make them really optional (or, third option, > > whether > > there's something I haven't understood properly). > > My plan is to make IOMMU groups mandatory. I am currently preparing and > RFC patch-set to introduce default-domains (which will be per group). So > when all IOMMU drivers are converted to make use of default domains the > iommu groups will be mandatory.
That makes sense to me, too. I think we should also consider extending the generic IOMMU device-tree binding to describe groups so that they can be instantiated by core code, without each driver having to work things out for itself. Will -- To unsubscribe from this list: send the line "unsubscribe linux-samsung-soc" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
