add optional 2nd stage initialization to -object/object-add commands

Introduces USER_CREATABLE interface that must be implemented by
objects which are designed to created with -object CLI option or
object-add QMP command.

Interface provides an ability to do an optional second stage
initialization of the object created with -object/object-add
commands. By providing complete() callback, which is called
after the object properties were set.

It allows to:
 * prevents misusing of -object/object-add by filtering out
   objects that are not designed for it.
 * generalize second stage backend initialization instead of
   adding custom APIs to perform it
 * early error detection of backend initialization at -object/
   object-add time rather than through a proxy DEVICE object
   that tries to use backend.

Signed-off-by: Igor Mammedov <imammedo@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>

1 files changed, 12 insertions, 0 deletions

diff --git a/qmp.c b/qmp.c
index a67e0c4539..d0d98e777b 100644
--- a/qmp.c
+++ b/qmp.c
@@ -27,6 +27,7 @@
 #include "qapi/qmp/qobject.h"
 #include "qapi/qmp-input-visitor.h"
 #include "hw/boards.h"
+#include "qom/object_interfaces.h"
 
 NameInfo *qmp_query_name(Error **errp)
 {
@@ -554,6 +555,17 @@ void object_add(const char *type, const char *id, const QDict *qdict,
         }
     }
 
+    if (!object_dynamic_cast(obj, TYPE_USER_CREATABLE)) {
+        error_setg(&local_err, "object '%s' isn't supported by object-add",
+                   id);
+        goto out;
+    }
+
+    user_creatable_complete(obj, &local_err);
+    if (local_err) {
+        goto out;
+    }
+
     object_property_add_child(container_get(object_get_root(), "/objects"),
                               id, obj, &local_err);
 out: