iommu: Allow taking a reference on a group directly

iommu_group_get_for_dev() expects that the IOMMU driver's device_group
callback return a group with a reference held for the given device.
Whilst allocating a new group is fine, and pci_device_group() correctly
handles reusing an existing group, there is no general means for IOMMU
drivers doing their own group lookup to take additional references on an
existing group pointer without having to also store device pointers or
resort to elaborate trickery.

Add an IOMMU-driver-specific function to fill the hole.

Acked-by: Sricharan R <sricharan@codeaurora.org>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Signed-off-by: Joerg Roedel <jroedel@suse.de>

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 9a2f1960873b65e01b29ff5f1d84148ce4bae094..9408c3145483c4ce9dcb335b22f9bde1810779bb 100644 (file)
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -551,6 +551,19 @@ struct iommu_group *iommu_group_get(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(iommu_group_get);
 
+/**
+ * iommu_group_ref_get - Increment reference on a group
+ * @group: the group to use, must not be NULL
+ *
+ * This function is called by iommu drivers to take additional references on an
+ * existing group.  Returns the given group for convenience.
+ */
+struct iommu_group *iommu_group_ref_get(struct iommu_group *group)
+{
+       kobject_get(group->devices_kobj);
+       return group;
+}
+
 /**
  * iommu_group_put - Decrement group reference
  * @group: the group to use

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 436dc21318af776bd6c5a7ce8eae35aac995d349..431638110c6aedf9503ca1606109ed34eb87d555 100644 (file)
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -253,6 +253,7 @@ extern void iommu_group_remove_device(struct device *dev);
 extern int iommu_group_for_each_dev(struct iommu_group *group, void *data,
                                    int (*fn)(struct device *, void *));
 extern struct iommu_group *iommu_group_get(struct device *dev);
+extern struct iommu_group *iommu_group_ref_get(struct iommu_group *group);
 extern void iommu_group_put(struct iommu_group *group);
 extern int iommu_group_register_notifier(struct iommu_group *group,
                                         struct notifier_block *nb);