[Qemu-devel] [PATCH v3 07/20] qom: add child properties (composition) (v3)

[Anthony Liguori <aliguori@us.ibm.com>]

Child properties express a relationship of composition.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
---
v1 -> v2
 - fix comments (Kevin)
 - add a reference when adding a child property (Kevin)
 - fix bug spotted by Paolo on reference
---
 hw/qdev.c |   26 ++++++++++++++++++++++++++
 hw/qdev.h |   20 ++++++++++++++++++++
 2 files changed, 46 insertions(+), 0 deletions(-)

diff --git a/hw/qdev.c b/hw/qdev.c
index 2519f00..167f459 100644
--- a/hw/qdev.c
+++ b/hw/qdev.c
@@ -1174,6 +1174,32 @@ DeviceState *qdev_get_root(void)
     return qdev_root;
 }
 
+static void qdev_get_child_property(DeviceState *dev, Visitor *v, void *opaque,
+                                    const char *name, Error **errp)
+{
+    DeviceState *child = opaque;
+    gchar *path;
+
+    path = qdev_get_canonical_path(child);
+    visit_type_str(v, &path, name, errp);
+    g_free(path);
+}
+
+void qdev_property_add_child(DeviceState *dev, const char *name,
+                             DeviceState *child, Error **errp)
+{
+    gchar *type;
+
+    type = g_strdup_printf("child<%s>", child->info->name);
+
+    qdev_property_add(dev, name, type, qdev_get_child_property,
+                      NULL, NULL, child, errp);
+
+    qdev_ref(child);
+
+    g_free(type);
+}
+
 static gchar *qdev_get_path_in(DeviceState *parent, DeviceState *dev)
 {
     DeviceProperty *prop;
diff --git a/hw/qdev.h b/hw/qdev.h
index 641d134..38b36e8 100644
--- a/hw/qdev.h
+++ b/hw/qdev.h
@@ -527,4 +527,24 @@ gchar *qdev_get_canonical_path(DeviceState *dev);
  */
 DeviceState *qdev_resolve_path(const char *path, bool *ambiguous);
 
+/**
+ * @qdev_property_add_child - Add a child property to a device
+ *
+ * Child properties form the composition tree.  All devices need to be a child
+ * of another device.  Devices can only be a child of one device.
+ *
+ * There is no way for a child to determine what its parent is.  It is not
+ * a bidirectional relationship.  This is by design.
+ *
+ * @dev - the device to add a property to
+ *
+ * @name - the name of the property
+ *
+ * @child - the child device
+ *
+ * @errp - if an error occurs, a pointer to an area to store the area
+ */
+void qdev_property_add_child(DeviceState *dev, const char *name,
+                             DeviceState *child, Error **errp);
+
 #endif
-- 
1.7.4.1