---
include/qemu/object.h | 76 +++++++++++++++++++++++++++++++++++++++++++++++--
1 files changed, 73 insertions(+), 3 deletions(-)
diff --git a/include/qemu/object.h b/include/qemu/object.h
index ab1c48c..ad7d32d 100644
--- a/include/qemu/object.h
+++ b/include/qemu/object.h
@@ -55,6 +55,9 @@ typedef struct InterfaceInfo InterfaceInfo;
*
* #define TYPE_MY_DEVICE "my-device"
*
+ * // No new virtual functions: we can reuse the typedef for the
+ * // superclass.
+ * typedef DeviceClass MyDeviceClass;
* typedef struct MyDevice
* {
* DeviceState parent;
@@ -88,8 +91,21 @@ typedef struct InterfaceInfo InterfaceInfo;
*
* Using object_new(), a new #Object derivative will be instantiated. You can
* cast an #Object to a subclass (or base-class) type using
- * object_dynamic_cast(). You typically want to define a macro wrapper around
- * object_dynamic_cast_assert() to make it easier to convert to a specific
type.
+ * object_dynamic_cast(). You typically want to define macro wrappers around
+ * OBJECT_CHECK() and OBJECT_CLASS_CHECK() to make it easier to convert to a
+ * specific type:
+ *
+ *<example>
+ *<title>Typecasting macros</title>
+ *<programlisting>
+ * #define MY_DEVICE_GET_CLASS(obj) \
+ * OBJECT_GET_CLASS(MyDeviceClass, obj, TYPE_MY_DEVICE)
+ * #define MY_DEVICE_CLASS(klass) \
+ * OBJECT_CLASS_CHECK(MyDeviceClass, klass, TYPE_MY_DEVICE)
+ * #define MY_DEVICE(obj) \
+ * OBJECT_CHECK(MyDevice, obj, TYPE_MY_DEVICE)
+ *</programlisting>
+ *</example>
*
* # Class Initialization #
*
@@ -108,7 +124,61 @@ typedef struct InterfaceInfo InterfaceInfo;
*
* Once all of the parent classes have been initialized, #TypeInfo::class_init
* is called to let the class being instantiated provide default initialize
for
- * it's virtual functions.
+ * it's virtual functions. Here is how the above example might be modified
+ * to introduce an overridden virtual function:
+ *
+ *<example>
+ *<title>Overriding a virtual function</title>
+ *<programlisting>
+ * #include "qdev.h"
+ *
+ * void my_device_class_init(ObjectClass *klass, void *class_data)
+ * {
+ * DeviceClass *dc = DEVICE_CLASS(klass);
+ * dc->reset = my_device_reset;
+ * }
+ *
+ * static TypeInfo my_device_info = {
+ * .name = TYPE_MY_DEVICE,
+ * .parent = TYPE_DEVICE,
+ * .instance_size = sizeof(MyDevice),
+ * .class_init = my_device_class_init,
+ * };
+ *</programlisting>
+ *</example>
+ *
+ * Introducing new virtual functions requires a class to define its own
+ * struct and to add a .class_size member to the TypeInfo. Each function
+ * will also have a wrapper to call it easily:
+ *
+ *<example>
+ *<title>Defining an abstract class</title>
+ *<programlisting>
+ * #include "qdev.h"
+ *
+ * typedef struct MyDeviceClass
+ * {
+ * DeviceClass parent;
+ *
+ * void (*frobnicate) (MyDevice *obj);
+ * } MyDeviceClass;
+ *
+ * static TypeInfo my_device_info = {
+ * .name = TYPE_MY_DEVICE,
+ * .parent = TYPE_DEVICE,
+ * .instance_size = sizeof(MyDevice),
+ * .abstract = true, // or set a default in my_device_class_init
+ * .class_size = sizeof(MyDeviceClass),
+ * };
+ *
+ * void my_device_frobnicate(MyDevice *obj)
+ * {
+ * MyDeviceClass *klass = MY_DEVICE_GET_CLASS(obj);
+ *
+ * klass->frobnicate(obj);
+ * }
+ *</programlisting>
+ *</example>
*
* # Interfaces #
*