iommu: Introduce iommu_request_dm_for_dev()

This function can be called by an IOMMU driver to request
that a device's default domain is direct mapped.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index b944b2b..dc767f7 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -225,6 +225,7 @@
 
 extern void iommu_get_dm_regions(struct device *dev, struct list_head *list);
 extern void iommu_put_dm_regions(struct device *dev, struct list_head *list);
+extern int iommu_request_dm_for_dev(struct device *dev);
 
 extern int iommu_attach_group(struct iommu_domain *domain,
 			      struct iommu_group *group);
@@ -411,6 +412,11 @@
 {
 }
 
+static inline int iommu_request_dm_for_dev(struct device *dev)
+{
+	return -ENODEV;
+}
+
 static inline int iommu_attach_group(struct iommu_domain *domain,
 				     struct iommu_group *group)
 {