qdev: make properties array "const"

Constify all accesses to qdev properties, except for the
ObjectPropertyAccessor itself.  This makes it possible to place them in
read-only memory, and also lets Rust bindings switch from "static mut"
arrays to "static"; which is advantageous, because mutable statics are
highly discouraged.

Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/core/qdev-properties.c

@@ -749,7 +749,7 @@ const PropertyInfo qdev_prop_array = {
 
 /* --- public helpers --- */
 
-static Property *qdev_prop_walk(Property *props, const char *name)
+static const Property *qdev_prop_walk(const Property *props, const char *name)
 {
     if (!props) {
         return NULL;
@@ -763,10 +763,10 @@ static Property *qdev_prop_walk(Property *props, const char *name)
     return NULL;
 }
 
-static Property *qdev_prop_find(DeviceState *dev, const char *name)
+static const Property *qdev_prop_find(DeviceState *dev, const char *name)
 {
     ObjectClass *class;
-    Property *prop;
+    const Property *prop;
 
     /* device properties */
     class = object_get_class(OBJECT(dev));
@@ -840,7 +840,7 @@ void qdev_prop_set_string(DeviceState *dev, const char *name, const char *value)
 
 void qdev_prop_set_enum(DeviceState *dev, const char *name, int value)
 {
-    Property *prop;
+    const Property *prop;
 
     prop = qdev_prop_find(dev, name);
     object_property_set_str(OBJECT(dev), name,
@@ -956,7 +956,7 @@ const PropertyInfo qdev_prop_size = {
 /* --- object link property --- */
 
 static ObjectProperty *create_link_property(ObjectClass *oc, const char *name,
-                                            Property *prop)
+                                            const Property *prop)
 {
     return object_class_property_add_link(oc, name, prop->link_type,
                                           prop->offset,
@@ -969,7 +969,7 @@ const PropertyInfo qdev_prop_link = {
     .create = create_link_property,
 };
 
-void qdev_property_add_static(DeviceState *dev, Property *prop)
+void qdev_property_add_static(DeviceState *dev, const Property *prop)
 {
     Object *obj = OBJECT(dev);
     ObjectProperty *op;
@@ -980,7 +980,7 @@ void qdev_property_add_static(DeviceState *dev, Property *prop)
                              field_prop_getter(prop->info),
                              field_prop_setter(prop->info),
                              prop->info->release,
-                             prop);
+                             (Property *)prop);
 
     object_property_set_description(obj, prop->name,
                                     prop->info->description);
@@ -994,7 +994,7 @@ void qdev_property_add_static(DeviceState *dev, Property *prop)
 }
 
 static void qdev_class_add_property(DeviceClass *klass, const char *name,
-                                    Property *prop)
+                                    const Property *prop)
 {
     ObjectClass *oc = OBJECT_CLASS(klass);
     ObjectProperty *op;
@@ -1007,7 +1007,7 @@ static void qdev_class_add_property(DeviceClass *klass, const char *name,
                                        field_prop_getter(prop->info),
                                        field_prop_setter(prop->info),
                                        prop->info->release,
-                                       prop);
+                                       (Property *)prop);
     }
     if (prop->set_default) {
         prop->info->set_default_value(op, prop);
@@ -1046,7 +1046,7 @@ static void qdev_get_legacy_property(Object *obj, Visitor *v,
  * Do not use this in new code!  QOM Properties added through this interface
  * will be given names in the "legacy" namespace.
  */
-static void qdev_class_add_legacy_property(DeviceClass *dc, Property *prop)
+static void qdev_class_add_legacy_property(DeviceClass *dc, const Property *prop)
 {
     g_autofree char *name = NULL;
 
@@ -1058,12 +1058,12 @@ static void qdev_class_add_legacy_property(DeviceClass *dc, Property *prop)
     name = g_strdup_printf("legacy-%s", prop->name);
     object_class_property_add(OBJECT_CLASS(dc), name, "str",
         prop->info->print ? qdev_get_legacy_property : prop->info->get,
-        NULL, NULL, prop);
+        NULL, NULL, (Property *)prop);
 }
 
-void device_class_set_props(DeviceClass *dc, Property *props)
+void device_class_set_props(DeviceClass *dc, const Property *props)
 {
-    Property *prop;
+    const Property *prop;
 
     dc->props_ = props;
     for (prop = props; prop && prop->name; prop++) {

include/hw/qdev-core.h

@@ -132,7 +132,7 @@ struct DeviceClass {
      * ensures a compile-time error if someone attempts to assign
      * dc->props directly.
      */
-    Property *props_;
+    const Property *props_;
 
     /**
      * @user_creatable: Can user instantiate with -device / device_add?
@@ -935,7 +935,7 @@ char *qdev_get_own_fw_dev_path_from_handler(BusState *bus, DeviceState *dev);
  * you attempt to add an existing property defined by a parent class.
  * To modify an inherited property you need to use????
  */
-void device_class_set_props(DeviceClass *dc, Property *props);
+void device_class_set_props(DeviceClass *dc, const Property *props);
 
 /**
  * device_class_set_parent_realize() - set up for chaining realize fns

include/hw/qdev-properties.h

@@ -37,7 +37,7 @@ struct PropertyInfo {
     int (*print)(Object *obj, Property *prop, char *dest, size_t len);
     void (*set_default_value)(ObjectProperty *op, const Property *prop);
     ObjectProperty *(*create)(ObjectClass *oc, const char *name,
-                              Property *prop);
+                              const Property *prop);
     ObjectPropertyAccessor *get;
     ObjectPropertyAccessor *set;
     ObjectPropertyRelease *release;
@@ -223,7 +223,7 @@ void error_set_from_qdev_prop_error(Error **errp, int ret, Object *obj,
  * On error, store error in @errp.  Static properties access data in a struct.
  * The type of the QOM property is derived from prop->info.
  */
-void qdev_property_add_static(DeviceState *dev, Property *prop);
+void qdev_property_add_static(DeviceState *dev, const Property *prop);
 
 /**
  * qdev_alias_all_properties: Create aliases on source for all target properties

system/qdev-monitor.c

@@ -751,7 +751,7 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
 
 #define qdev_printf(fmt, ...) monitor_printf(mon, "%*s" fmt, indent, "", ## __VA_ARGS__)
 
-static void qdev_print_props(Monitor *mon, DeviceState *dev, Property *props,
+static void qdev_print_props(Monitor *mon, DeviceState *dev, const Property *props,
                              int indent)
 {
     if (!props)