iommu: make the pointer to struct bus_type constant

A number of iommu functions take a struct bus_type * and never modify
the data passed in, so make them all const * as that is what the driver
core is expecting to have passed into as well.

This is a step toward making all struct bus_type pointers constant in
the kernel.

Cc: Will Deacon <[e-mail]>
Cc: Robin Murphy <[e-mail]>
Cc: [e-mail]
Acked-by: Joerg Roedel <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

drivers/iommu/iommu.c

···
 			      unsigned long action, void *data);
 static int iommu_alloc_default_domain(struct iommu_group *group,
 				      struct device *dev);
-static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
+static struct iommu_domain *__iommu_domain_alloc(const struct bus_type *bus,
 						 unsigned type);
 static int __iommu_attach_device(struct iommu_domain *domain,
 				 struct device *dev);
···
 	return 0;
 }
 
-static int iommu_group_alloc_default_domain(struct bus_type *bus,
+static int iommu_group_alloc_default_domain(const struct bus_type *bus,
 					    struct iommu_group *group,
 					    unsigned int type)
 {
···
 	return 0;
 }
 
-static void probe_alloc_default_domain(struct bus_type *bus,
+static void probe_alloc_default_domain(const struct bus_type *bus,
 				       struct iommu_group *group)
 {
 	struct __group_domain_type gtype;
···
 					  iommu_do_create_direct_mappings);
 }
 
-int bus_iommu_probe(struct bus_type *bus)
+int bus_iommu_probe(const struct bus_type *bus)
 {
 	struct iommu_group *group, *next;
 	LIST_HEAD(group_list);
···
 	return ret;
 }
 
-bool iommu_present(struct bus_type *bus)
+bool iommu_present(const struct bus_type *bus)
 {
 	return bus->iommu_ops != NULL;
 }
···
 }
 EXPORT_SYMBOL_GPL(iommu_set_fault_handler);
 
-static struct iommu_domain *__iommu_domain_alloc(struct bus_type *bus,
+static struct iommu_domain *__iommu_domain_alloc(const struct bus_type *bus,
 						 unsigned type)
 {
 	struct iommu_domain *domain;
···
 	return domain;
 }
 
-struct iommu_domain *iommu_domain_alloc(struct bus_type *bus)
+struct iommu_domain *iommu_domain_alloc(const struct bus_type *bus)
 {
 	return __iommu_domain_alloc(bus, IOMMU_DOMAIN_UNMANAGED);
 }

include/linux/iommu.h

···
 	return dev->iommu->iommu_dev->ops;
 }
 
-extern int bus_iommu_probe(struct bus_type *bus);
-extern bool iommu_present(struct bus_type *bus);
+extern int bus_iommu_probe(const struct bus_type *bus);
+extern bool iommu_present(const struct bus_type *bus);
 extern bool device_iommu_capable(struct device *dev, enum iommu_cap cap);
 extern bool iommu_group_has_isolated_msi(struct iommu_group *group);
-extern struct iommu_domain *iommu_domain_alloc(struct bus_type *bus);
+extern struct iommu_domain *iommu_domain_alloc(const struct bus_type *bus);
 extern struct iommu_group *iommu_group_get_by_id(int id);
 extern void iommu_domain_free(struct iommu_domain *domain);
 extern int iommu_attach_device(struct iommu_domain *domain,
···
 struct iommu_fault_param {};
 struct iommu_iotlb_gather {};
 
-static inline bool iommu_present(struct bus_type *bus)
+static inline bool iommu_present(const struct bus_type *bus)
 {
 	return false;
 }
···
 	return false;
 }
 
-static inline struct iommu_domain *iommu_domain_alloc(struct bus_type *bus)
+static inline struct iommu_domain *iommu_domain_alloc(const struct bus_type *bus)
 {
 	return NULL;
 }