qom: Reimplement Interfaces

The current implementation of Interfaces is poorly designed.  Each interface
that an object implements ends up being an object that's tracked by the
implementing object.  There's all sorts of gymnastics to deal with casting
between these objects.

But an interface shouldn't be associated with an Object.  Interfaces are global
to a class.  This patch moves all Interface knowledge to ObjectClass eliminating
the relationship between Object and Interfaces.

Interfaces are now abstract (as they should be) but this is okay.  Interfaces
essentially act as additional parents for the classes and are treated as such.

With this new implementation, we should fully support derived interfaces
including reimplementing an inherited interface.

PC: Rebased against qom-next merge Jun-2012.

PC: Removed replication of cast logic for interfaces, i.e. there is only
one cast function - object_dynamic_cast() (and object_dynamic_cast_assert())

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Peter A. G. Crosthwaite <peter.crosthwaite@petalogix.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Edgar E. Iglesias <edgar.iglesias@gmail.com>

1 files changed, 30 insertions, 16 deletions

diff --git a/include/qemu/object.h b/include/qemu/object.h
index 8b17776bb3..cc75feed66 100644
--- a/include/qemu/object.h
+++ b/include/qemu/object.h
@@ -239,6 +239,7 @@ struct ObjectClass
 {
     /*< private >*/
     Type type;
+    GSList *interfaces;
 };
 
 /**
@@ -260,7 +261,6 @@ struct Object
 {
     /*< private >*/
     ObjectClass *class;
-    GSList *interfaces;
     QTAILQ_HEAD(, ObjectProperty) properties;
     uint32_t ref;
     Object *parent;
@@ -387,6 +387,16 @@ struct TypeInfo
     OBJECT_CLASS_CHECK(class, object_get_class(OBJECT(obj)), name)
 
 /**
+ * InterfaceInfo:
+ * @type: The name of the interface.
+ *
+ * The information associated with an interface.
+ */
+struct InterfaceInfo {
+    const char *type;
+};
+
+/**
  * InterfaceClass:
  * @parent_class: the base class
  *
@@ -396,26 +406,30 @@ struct TypeInfo
 struct InterfaceClass
 {
     ObjectClass parent_class;
+    /*< private >*/
+    ObjectClass *concrete_class;
 };
 
+#define TYPE_INTERFACE "interface"
+
 /**
- * InterfaceInfo:
- * @type: The name of the interface.
- * @interface_initfn: This method is called during class initialization and is
- *   used to initialize an interface associated with a class.  This function
- *   should initialize any default virtual functions for a class and/or override
- *   virtual functions in a parent class.
- *
- * The information associated with an interface.
+ * INTERFACE_CLASS:
+ * @klass: class to cast from
+ * Returns: An #InterfaceClass or raise an error if cast is invalid
  */
-struct InterfaceInfo
-{
-    const char *type;
+#define INTERFACE_CLASS(klass) \
+    OBJECT_CLASS_CHECK(InterfaceClass, klass, TYPE_INTERFACE)
 
-    void (*interface_initfn)(ObjectClass *class, void *data);
-};
-
-#define TYPE_INTERFACE "interface"
+/**
+ * INTERFACE_CHECK:
+ * @interface: the type to return
+ * @obj: the object to convert to an interface
+ * @name: the interface type name
+ *
+ * Returns: @obj casted to @interface if cast is valid, otherwise raise error.
+ */
+#define INTERFACE_CHECK(interface, obj, name) \
+    ((interface *)object_dynamic_cast_assert(OBJECT((obj)), (name)))
 
 /**
  * object_new: