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iommu: Add a function to find an iommu group by id 

As IOMMU groups are exposed to the user space by their numbers,
the user space can use them in various kernel APIs so the kernel
might need an API to find a group by its ID.

As an example, QEMU VFIO on PPC64 platform needs it to associate
a logical bus number (LIOBN) with a specific IOMMU group in order
to support in-kernel handling of DMA map/unmap requests.

The patch adds the iommu_group_get_by_id(id) function which performs
such search.

v2: fixed reference counting.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Acked-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>
This commit is contained in:
Alexey Kardashevskiy 2013-03-25 10:23:49 +11:00 committed by Joerg Roedel
parent 61e015ac5b
commit aa16bea929
2 changed files with 30 additions and 0 deletions
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29
drivers/iommu/iommu.c
View File

@ -204,6 +204,35 @@ again:
}
EXPORT_SYMBOL_GPL(iommu_group_alloc);
struct iommu_group *iommu_group_get_by_id(int id)
{
struct kobject *group_kobj;
struct iommu_group *group;
const char *name;
if (!iommu_group_kset)
return NULL;
name = kasprintf(GFP_KERNEL, "%d", id);
if (!name)
return NULL;
group_kobj = kset_find_obj(iommu_group_kset, name);
kfree(name);
if (!group_kobj)
return NULL;
group = container_of(group_kobj, struct iommu_group, kobj);
BUG_ON(group->id != id);
kobject_get(group->devices_kobj);
kobject_put(&group->kobj);
return group;
}
EXPORT_SYMBOL_GPL(iommu_group_get_by_id);
/**
* iommu_group_get_iommudata - retrieve iommu_data registered for a group
* @group: the group

1
include/linux/iommu.h
View File

@ -126,6 +126,7 @@ struct iommu_ops {
extern int bus_set_iommu(struct bus_type *bus, struct iommu_ops *ops);
extern bool iommu_present(struct bus_type *bus);
extern struct iommu_domain *iommu_domain_alloc(struct bus_type *bus);
extern struct iommu_group *iommu_group_get_by_id(int id);
extern void iommu_domain_free(struct iommu_domain *domain);
extern int iommu_attach_device(struct iommu_domain *domain,
struct device *dev);