qapi: add support for command options

Options allow for changes in commands behavior. This commit introduces
the QCO_NO_SUCCESS_RESP option, which causes a command to not emit a
success response.

This is needed by commands such as qemu-ga's guest-shutdown, which
may not be able to complete before the VM vanishes. In this case, it's
useful and simpler not to bother sending a success response.

Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/qapi/qmp-dispatch.c b/qapi/qmp-dispatch.c
index 43f640a95e..122c1a29ba 100644
--- a/qapi/qmp-dispatch.c
+++ b/qapi/qmp-dispatch.c
@@ -94,8 +94,12 @@ static QObject *do_qmp_dispatch(QObject *request, Error **errp)
     switch (cmd->type) {
     case QCT_NORMAL:
         cmd->fn(args, &ret, errp);
-        if (!error_is_set(errp) && ret == NULL) {
-            ret = QOBJECT(qdict_new());
+        if (!error_is_set(errp)) {
+            if (cmd->options & QCO_NO_SUCCESS_RESP) {
+                g_assert(!ret);
+            } else if (!ret) {
+                ret = QOBJECT(qdict_new());
+            }
         }
         break;
     }