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

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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
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@@ -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