[PATCH 1/5] iommu: Allow taking a reference on a group directly
Will Deacon
will.deacon at arm.com
Wed Nov 9 09:25:43 PST 2016
On Wed, Nov 09, 2016 at 12:47:24PM +0000, Robin Murphy wrote:
> 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.
>
> Signed-off-by: Robin Murphy <robin.murphy at arm.com>
> ---
> drivers/iommu/iommu.c | 14 ++++++++++++++
> include/linux/iommu.h | 1 +
> 2 files changed, 15 insertions(+)
>
> diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
> index 9a2f1960873b..b0b052bc6bb5 100644
> --- a/drivers/iommu/iommu.c
> +++ b/drivers/iommu/iommu.c
> @@ -552,6 +552,20 @@ struct iommu_group *iommu_group_get(struct device *dev)
> EXPORT_SYMBOL_GPL(iommu_group_get);
>
> /**
> + * __iommu_group_get - Increment reference on a group
> + * @group: the group to use, must not be NULL
> + *
> + * This function may be called by internal iommu driver group management
> + * when the context of a struct device pointer is not available. It is
> + * not for general use. Returns the given group for convenience.
> + */
> +struct iommu_group *__iommu_group_get(struct iommu_group *group)
> +{
> + kobject_get(group->devices_kobj);
> + return group;
> +}
This probably either wants sticking in a header or exporting to modules.
That said, why do we need the underscores and the comment about internal
group management? That's pretty much already the case for iommu_group_get.
Of course, removing the underscores gives you a naming conflict, but we
could just call it something like "iommu_group_get_ref".
Will
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