iommu: Add generic_device_group() function

This function can be used as a device_group call-back and
just allocates one iommu-group per device.
Signed-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/iommu.c

@@ -727,6 +727,21 @@ static int get_pci_alias_or_group(struct pci_dev *pdev, u16 alias, void *opaque)
 	return data->group != NULL;
 }
 
+/*
+ * Generic device_group call-back function. It just allocates one
+ * iommu-group per device.
+ */
+struct iommu_group *generic_device_group(struct device *dev)
+{
+	struct iommu_group *group;
+
+	group = iommu_group_alloc();
+	if (IS_ERR(group))
+		return NULL;
+
+	return group;
+}
+
 /*
  * Use standard PCI bus topology, isolation features, and DMA alias quirks
  * to find or create an IOMMU group for a device.

include/linux/iommu.h

@@ -319,6 +319,8 @@ static inline size_t iommu_map_sg(struct iommu_domain *domain,
 
 /* PCI device grouping function */
 extern struct iommu_group *pci_device_group(struct device *dev);
+/* Generic device grouping function */
+extern struct iommu_group *generic_device_group(struct device *dev);
 
 #else /* CONFIG_IOMMU_API */