Re: [PATCH 01/13] driver core: Add iommu_group tracking to struct device

[Greg KH <gregkh@linuxfoundation.org>]

On Fri, May 11, 2012 at 05:58:01PM -0600, Alex Williamson wrote:
> On Fri, 2012-05-11 at 16:38 -0700, Greg KH wrote:
> > On Fri, May 11, 2012 at 04:55:35PM -0600, Alex Williamson wrote:
> > > IOMMU groups allow IOMMU drivers to represent DMA visibility
> > > and isolation of devices.  Multiple devices may be grouped
> > > together for the purposes of DMA.  Placing a pointer on
> > > struct device enable easy access for things like streaming
> > > DMA programming and drivers like VFIO.
> > > 
> > > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> > 
> > Can't you get this today from the iommu_ops pointer that is on the bus
> > that the device is associated with?  Or can devices on a bus have
> > different iommu_group pointers?
> 
> The latter, each device on a bus might be it's own group.  This is often
> the case on x86 unless PCIe-to-PCI bridges obscure the device
> visibility.  Thanks,

Ah, ok, then I have no objection to add this to struct device:

Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>