qapi/qom: QAPIfy object-add

This converts object-add from 'gen': false to the ObjectOptions QAPI
type. As an immediate benefit, clients can now use QAPI schema
introspection for user creatable QOM objects.

It is also the first step towards making the QAPI schema the only
external interface for the creation of user creatable objects. Once all
other places (HMP and command lines of the system emulator and all
tools) go through QAPI, too, some object implementations can be
simplified because some checks (e.g. that mandatory options are set) are
already performed by QAPI, and in another step, QOM boilerplate code
could be generated from the schema.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Peter Krempa <pkrempa@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

hw/block/xen-block.c

@@ -836,17 +836,17 @@ static XenBlockIOThread *xen_block_iothread_create(const char *id,
 {
     ERRP_GUARD();
     XenBlockIOThread *iothread = g_new(XenBlockIOThread, 1);
-    QDict *opts;
-    QObject *ret_data = NULL;
+    ObjectOptions *opts;
 
     iothread->id = g_strdup(id);
 
-    opts = qdict_new();
-    qdict_put_str(opts, "qom-type", TYPE_IOTHREAD);
-    qdict_put_str(opts, "id", id);
-    qmp_object_add(opts, &ret_data, errp);
-    qobject_unref(opts);
-    qobject_unref(ret_data);
+    opts = g_new(ObjectOptions, 1);
+    *opts = (ObjectOptions) {
+        .qom_type = OBJECT_TYPE_IOTHREAD,
+        .id = g_strdup(id),
+    };
+    qmp_object_add(opts, errp);
+    qapi_free_ObjectOptions(opts);
 
     if (*errp) {
         g_free(iothread->id);

include/qom/object_interfaces.h

@@ -196,11 +196,4 @@ bool user_creatable_del(const char *id, Error **errp);
  */
 void user_creatable_cleanup(void);
 
-/**
- * qmp_object_add:
- *
- * QMP command handler for object-add. See the QAPI schema for documentation.
- */
-void qmp_object_add(QDict *qdict, QObject **ret_data, Error **errp);
-
 #endif

monitor/misc.c

@@ -235,8 +235,6 @@ static void monitor_init_qmp_commands(void)
                          qmp_query_qmp_schema, QCO_ALLOW_PRECONFIG);
     qmp_register_command(&qmp_commands, "device_add", qmp_device_add,
                          QCO_NO_OPTIONS);
-    qmp_register_command(&qmp_commands, "object-add", qmp_object_add,
-                         QCO_NO_OPTIONS);
 
     QTAILQ_INIT(&qmp_cap_negotiation_commands);
     qmp_register_command(&qmp_cap_negotiation_commands, "qmp_capabilities",

qapi/qom.json

@@ -846,13 +846,6 @@
 #
 # Create a QOM object.
 #
-# @qom-type: the class name for the object to be created
-#
-# @id: the name of the new object
-#
-# Additional arguments depend on qom-type and are passed to the backend
-# unchanged.
-#
 # Returns: Nothing on success
 #          Error if @qom-type is not a valid class name
 #
@@ -866,9 +859,7 @@
 # <- { "return": {} }
 #
 ##
-{ 'command': 'object-add',
-  'data': {'qom-type': 'str', 'id': 'str'},
-  'gen': false } # so we can get the additional arguments
+{ 'command': 'object-add', 'data': 'ObjectOptions', 'boxed': true }
 
 ##
 # @object-del:

qom/qom-qmp-cmds.c

@@ -19,8 +19,11 @@
 #include "qapi/error.h"
 #include "qapi/qapi-commands-qdev.h"
 #include "qapi/qapi-commands-qom.h"
+#include "qapi/qapi-visit-qom.h"
 #include "qapi/qmp/qdict.h"
 #include "qapi/qmp/qerror.h"
+#include "qapi/qobject-input-visitor.h"
+#include "qapi/qobject-output-visitor.h"
 #include "qemu/cutils.h"
 #include "qom/object_interfaces.h"
 #include "qom/qom-qobject.h"
@@ -223,9 +226,27 @@ ObjectPropertyInfoList *qmp_qom_list_properties(const char *typename,
     return prop_list;
 }
 
-void qmp_object_add(QDict *qdict, QObject **ret_data, Error **errp)
+void qmp_object_add(ObjectOptions *options, Error **errp)
 {
-    user_creatable_add_dict(qdict, false, errp);
+    Visitor *v;
+    QObject *qobj;
+    QDict *props;
+    Object *obj;
+
+    v = qobject_output_visitor_new(&qobj);
+    visit_type_ObjectOptions(v, NULL, &options, &error_abort);
+    visit_complete(v, &qobj);
+    visit_free(v);
+
+    props = qobject_to(QDict, qobj);
+    qdict_del(props, "qom-type");
+    qdict_del(props, "id");
+
+    v = qobject_input_visitor_new(QOBJECT(props));
+    obj = user_creatable_add_type(ObjectType_str(options->qom_type),
+                                  options->id, props, v, errp);
+    object_unref(obj);
+    visit_free(v);
 }
 
 void qmp_object_del(const char *id, Error **errp)

storage-daemon/qemu-storage-daemon.c

@@ -148,8 +148,6 @@ static void init_qmp_commands(void)
     qmp_init_marshal(&qmp_commands);
     qmp_register_command(&qmp_commands, "query-qmp-schema",
                          qmp_query_qmp_schema, QCO_ALLOW_PRECONFIG);
-    qmp_register_command(&qmp_commands, "object-add", qmp_object_add,
-                         QCO_NO_OPTIONS);
 
     QTAILQ_INIT(&qmp_cap_negotiation_commands);
     qmp_register_command(&qmp_cap_negotiation_commands, "qmp_capabilities",