3 files changed, 39 insertions, 0 deletions

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 30b064497486..3343264f5105 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -34,6 +34,37 @@ void register_iommu(struct iommu_ops *ops)
         iommu_ops = ops;
 }
 
+static void iommu_bus_init(struct bus_type *bus, struct iommu_ops *ops)
+{
+}
+
+/**
+ * bus_set_iommu - set iommu-callbacks for the bus
+ * @bus: bus.
+ * @ops: the callbacks provided by the iommu-driver
+ *
+ * This function is called by an iommu driver to set the iommu methods
+ * used for a particular bus. Drivers for devices on that bus can use
+ * the iommu-api after these ops are registered.
+ * This special function is needed because IOMMUs are usually devices on
+ * the bus itself, so the iommu drivers are not initialized when the bus
+ * is set up. With this function the iommu-driver can set the iommu-ops
+ * afterwards.
+ */
+int bus_set_iommu(struct bus_type *bus, struct iommu_ops *ops)
+{
+        if (bus->iommu_ops != NULL)
+                return -EBUSY;
+
+        bus->iommu_ops = ops;
+
+        /* Do IOMMU specific setup for this bus-type */
+        iommu_bus_init(bus, ops);
+
+        return 0;
+}
+EXPORT_SYMBOL_GPL(bus_set_iommu);
+
 bool iommu_found(void)
 {
         return iommu_ops != NULL;
diff --git a/include/linux/device.h b/include/linux/device.h
index c20dfbfc49b4..e838e143baa7 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -33,6 +33,7 @@ struct class;
 struct subsys_private;
 struct bus_type;
 struct device_node;
+struct iommu_ops;
 
 struct bus_attribute {
         struct attribute        attr;
@@ -67,6 +68,9 @@ extern void bus_remove_file(struct bus_type *, struct bus_attribute *);
  * @resume:     Called to bring a device on this bus out of sleep mode.
  * @pm:         Power management operations of this bus, callback the specific
  *              device driver's pm-ops.
+ * @iommu_ops   IOMMU specific operations for this bus, used to attach IOMMU
+ *              driver implementations to a bus and allow the driver to do
+ *              bus-specific setup
  * @p:          The private data of the driver core, only the driver core can
  *              touch this.
  *
@@ -96,6 +100,8 @@ struct bus_type {
 
         const struct dev_pm_ops *pm;
 
+        struct iommu_ops *iommu_ops;
+
         struct subsys_private *p;
 };
 
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 6470cd87b4ea..dca83d3405b1 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -25,6 +25,7 @@
 #define IOMMU_WRITE     (2)
 #define IOMMU_CACHE     (4) /* DMA cache coherency */
 
+struct bus_type;
 struct device;
 
 struct iommu_domain {
@@ -52,6 +53,7 @@ struct iommu_ops {
 };
 
 extern void register_iommu(struct iommu_ops *ops);
+extern int bus_set_iommu(struct bus_type *bus, struct iommu_ops *ops);
 extern bool iommu_found(void);
 extern struct iommu_domain *iommu_domain_alloc(void);
 extern void iommu_domain_free(struct iommu_domain *domain);