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, 13 insertions, 0 deletions

diff --git a/vl.c b/vl.c
index cf3de56b7d..9c2619f271 100644
--- a/vl.c
+++ b/vl.c
@@ -170,6 +170,7 @@ int main(int argc, char **argv)
 
 #include "ui/qemu-spice.h"
 #include "qapi/string-input-visitor.h"
+#include "qom/object_interfaces.h"
 
 //#define DEBUG_NET
 //#define DEBUG_SLIRP
@@ -2816,9 +2817,21 @@ static int object_create(QemuOpts *opts, void *opaque)
         return -1;
     }
 
+    if (!object_dynamic_cast(obj, TYPE_USER_CREATABLE)) {
+        error_setg(&local_err, "object '%s' isn't supported by -object",
+                   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:
     object_unref(obj);
     if (local_err) {
         qerror_report_err(local_err);