[PATCH v4 30/35] qom: add method for getting the "id" of a QOM object

["Daniel P. Berrangé" <berrange@redhat.com>]

The 'user_creatable_del' method doesn't want the 'Object *', but
instead the "id" of the object to be deleted. While most of its
work could be done with the "Object *" alone, purging the QemuOpts
values needs the "id".

The "id" is not recorded against an Object though, it is indirectly
stored as a property linking the parent and child objects together.
Add an accessor that can fetch this property name.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
---
 include/qom/object.h | 10 ++++++++++
 qom/object.c         | 17 +++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/include/qom/object.h b/include/qom/object.h
index 11f55613fc..216d2a30f6 100644
--- a/include/qom/object.h
+++ b/include/qom/object.h
@@ -1759,6 +1759,16 @@ ObjectProperty *object_property_try_add_child(Object *obj, const char *name,
 ObjectProperty *object_property_add_child(Object *obj, const char *name,
                                           Object *child);
 
+/**
+ * object_property_get_child_name:
+ * @obj: the object that owns the property
+ * @child: the object referenced by the child property
+ *
+ * Return the property name against which @child is registered
+ * with @obj, or NULL if @obj is not a parent of @child.
+ */
+char *object_property_get_child_name(Object *obj, Object *child);
+
 typedef enum {
     /* Unref the link pointer when the property is deleted */
     OBJ_PROP_LINK_STRONG = 0x1,
diff --git a/qom/object.c b/qom/object.c
index f79b2cf361..66bbd1488b 100644
--- a/qom/object.c
+++ b/qom/object.c
@@ -1952,6 +1952,23 @@ object_property_add_child(Object *obj, const char *name,
     return object_property_try_add_child(obj, name, child, &error_abort);
 }
 
+char *object_property_get_child_name(Object *obj, Object *child)
+{
+    ObjectProperty *prop;
+    GHashTableIter iter;
+    gpointer key, value;
+
+    g_hash_table_iter_init(&iter, obj->properties);
+    while (g_hash_table_iter_next(&iter, &key, &value)) {
+        prop = value;
+        if (object_property_is_child(prop) && prop->opaque == child) {
+            return g_strdup(prop->name);
+        }
+    }
+    return NULL;
+}
+
+
 void object_property_allow_set_link(const Object *obj, const char *name,
                                     Object *val, Error **errp)
 {
-- 
2.54.0