tree f9802b729aa47d9c95fe2de5f41c511d3db7df4c
parent 1ea6b8f48918282bdca0b32a34095504ee65bab5
author Alex Williamson <alex.williamson@redhat.com> 1319226965 -0400
committer Joerg Roedel <joerg.roedel@amd.com> 1321356143 +0100

iommu: Add iommu_device_group callback and iommu_group sysfs entry

An IOMMU group is a set of devices for which the IOMMU cannot
distinguish transactions.  For PCI devices, a group often occurs
when a PCI bridge is involved.  Transactions from any device
behind the bridge appear to be sourced from the bridge itself.
We leave it to the IOMMU driver to define the grouping restraints
for their platform.

Using this new interface, the group for a device can be retrieved
using the iommu_device_group() callback.  Users will compare the
value returned against the value returned for other devices to
determine whether they are part of the same group.  Devices with
no group are not translated by the IOMMU.  There should be no
expectations about the group numbers as they may be arbitrarily
assigned by the IOMMU driver and may not be persistent across boots.

We also provide a sysfs interface to the group numbers here so
that userspace can understand IOMMU dependencies between devices
for managing safe, userspace drivers.

[Some code changes by Joerg Roedel <joerg.roedel@amd.com>]

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>