iommu: constify pointer to bus_type

Make pointer to bus_type a pointer to const for code safety.
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20240216144027.185959-1-krzysztof.kozlowski@linaro.orgSigned-off-by: Joerg Roedel <jroedel@suse.de>

drivers/iommu/iommu-priv.h

@@ -21,10 +21,11 @@ int iommu_group_replace_domain(struct iommu_group *group,
 			       struct iommu_domain *new_domain);
 
 int iommu_device_register_bus(struct iommu_device *iommu,
-			      const struct iommu_ops *ops, struct bus_type *bus,
+			      const struct iommu_ops *ops,
+			      const struct bus_type *bus,
 			      struct notifier_block *nb);
 void iommu_device_unregister_bus(struct iommu_device *iommu,
-				 struct bus_type *bus,
+				 const struct bus_type *bus,
 				 struct notifier_block *nb);
 
 #endif /* __LINUX_IOMMU_PRIV_H */

drivers/iommu/iommu.c

@@ -289,7 +289,7 @@ EXPORT_SYMBOL_GPL(iommu_device_unregister);
 
 #if IS_ENABLED(CONFIG_IOMMUFD_TEST)
 void iommu_device_unregister_bus(struct iommu_device *iommu,
-				 struct bus_type *bus,
+				 const struct bus_type *bus,
 				 struct notifier_block *nb)
 {
 	bus_unregister_notifier(bus, nb);
@@ -303,7 +303,8 @@ EXPORT_SYMBOL_GPL(iommu_device_unregister_bus);
  * some memory to hold a notifier_block.
  */
 int iommu_device_register_bus(struct iommu_device *iommu,
-			      const struct iommu_ops *ops, struct bus_type *bus,
+			      const struct iommu_ops *ops,
+			      const struct bus_type *bus,
 			      struct notifier_block *nb)
 {
 	int err;