[Qemu-devel] [PATCH 06/18] qom: add child properties (composition)

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

Child properties express a relationship of composition.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
---
 hw/qdev.c |   24 ++++++++++++++++++++++++
 hw/qdev.h |   20 ++++++++++++++++++++
 2 files changed, 44 insertions(+), 0 deletions(-)

diff --git a/hw/qdev.c b/hw/qdev.c
index 5bffbb7..b09d22a 100644
--- a/hw/qdev.c
+++ b/hw/qdev.c
@@ -1156,6 +1156,30 @@ 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);
+
+    g_free(type);
+}
+
 static gchar *qdev_get_path_in(DeviceState *parent, DeviceState *dev)
 {
     GSList *i;
diff --git a/hw/qdev.h b/hw/qdev.h
index b8b62f5..905a02c 100644
--- a/hw/qdev.h
+++ b/hw/qdev.h
@@ -499,4 +499,24 @@ 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 it's 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