The new callback will be used in following "object: add
object_property_set_defaut_{bool,str,int,uint}()" and "vl: print
default value in object help" patches.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
---
 include/qom/object.h | 17 +++++++++++++++++
 qom/object.c         |  9 +++++++++
 2 files changed, 26 insertions(+)

diff --git a/include/qom/object.h b/include/qom/object.h
index e15ebd486b..8d442cf633 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -361,6 +361,13 @@ typedef void (ObjectPropertyRelease)(Object *obj,
  */
 typedef void (ObjectPropertyInit)(Object *obj, ObjectProperty *prop);
 
+/**
+ * ObjectPropertyGetDefault:
+ *
+ * Get an allocated string representation of the default value.
+ */
+typedef char *(ObjectPropertyGetDefault)(ObjectProperty *prop);
+
 struct ObjectProperty
 {
     gchar *name;
@@ -371,6 +378,7 @@ struct ObjectProperty
     ObjectPropertyResolve *resolve;
     ObjectPropertyRelease *release;
     ObjectPropertyInit *init;
+    ObjectPropertyGetDefault *get_default;
     void *opaque;
 };
 
@@ -1214,6 +1222,15 @@ bool object_property_get_bool(Object *obj, const char *name,
 void object_property_set_int(Object *obj, int64_t value,
                              const char *name, Error **errp);
 
+/**
+ * object_property_get_defaut:
+ * @prop: the property to get default value
+ *
+ * Return an allocated string that represents the default property
+ * value or NULL.
+ */
+char *object_property_get_default(ObjectProperty *prop);
+
 /**
  * object_property_get_int:
  * @obj: the object
diff --git a/qom/object.c b/qom/object.c
index 4b9f8d8668..844a2d66bf 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1405,6 +1405,15 @@ int64_t object_property_get_int(Object *obj, const char *name,
     return retval;
 }
 
+char *object_property_get_default(ObjectProperty *prop)
+{
+    if (!prop->get_default) {
+        return NULL;
+    }
+
+    return prop->get_default(prop);
+}
+
 void object_property_set_uint(Object *obj, uint64_t value,
                               const char *name, Error **errp)
 {
-- 
2.24.0