qemu-ga: Extend 'guest-info' command to expose flag 'success-response'

Now we have several qemu-ga commands not returning response on success.
It has been documented in qga/qapi-schema.json already. This patch exposes
the 'success-response' flag by extending 'guest-info' command. With this
change, the clients can handle the command response more flexibly.

Signed-off-by: Mark Wu <wudxw@linux.vnet.ibm.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Michael Roth <mdroth@linux.vnet.ibm.com>
*fixed up commit subject
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

include/qapi/qmp/dispatch.h

@@ -49,6 +49,7 @@ void qmp_disable_command(const char *name);
 void qmp_enable_command(const char *name);
 bool qmp_command_is_enabled(const QmpCommand *cmd);
 const char *qmp_command_name(const QmpCommand *cmd);
+bool qmp_has_success_response(const QmpCommand *cmd);
 QObject *qmp_build_error_object(Error *errp);
 typedef void (*qmp_cmd_callback_fn)(QmpCommand *cmd, void *opaque);
 void qmp_for_each_command(qmp_cmd_callback_fn fn, void *opaque);

qapi/qmp-registry.c

@@ -76,6 +76,11 @@ const char *qmp_command_name(const QmpCommand *cmd)
     return cmd->name;
 }
 
+bool qmp_has_success_response(const QmpCommand *cmd)
+{
+    return !(cmd->options & QCO_NO_SUCCESS_RESP);
+}
+
 void qmp_for_each_command(qmp_cmd_callback_fn fn, void *opaque)
 {
     QmpCommand *cmd;

qga/commands.c

@@ -54,6 +54,7 @@ static void qmp_command_info(QmpCommand *cmd, void *opaque)
     cmd_info = g_malloc0(sizeof(GuestAgentCommandInfo));
     cmd_info->name = g_strdup(qmp_command_name(cmd));
     cmd_info->enabled = qmp_command_is_enabled(cmd);
+    cmd_info->success_response = qmp_has_success_response(cmd);
 
     cmd_info_list = g_malloc0(sizeof(GuestAgentCommandInfoList));
     cmd_info_list->value = cmd_info;

qga/qapi-schema.json

@@ -141,10 +141,13 @@
 #
 # @enabled: whether command is currently enabled by guest admin
 #
+# @success-response: whether command returns a response on success
+#                    (since 1.7)
+#
 # Since 1.1.0
 ##
 { 'type': 'GuestAgentCommandInfo',
-  'data': { 'name': 'str', 'enabled': 'bool' } }
+  'data': { 'name': 'str', 'enabled': 'bool', 'success-response': 'bool' } }
 
 ##
 # @GuestAgentInfo