monitor: Add chardev-add backend argument completion.

Signed-off-by: Hani Benhabiles <hani@linux.com>
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
diff --git a/monitor.c b/monitor.c
index 55e5696..ef5168b 100644
--- a/monitor.c
+++ b/monitor.c
@@ -4269,6 +4269,29 @@
     return (p != NULL ? ++p : typestr);
 }
 
+void chardev_add_completion(ReadLineState *rs, int nb_args, const char *str)
+{
+    size_t len;
+    ChardevBackendInfoList *list, *start;
+
+    if (nb_args != 2) {
+        return;
+    }
+    len = strlen(str);
+    readline_set_completion_index(rs, len);
+
+    start = list = qmp_query_chardev_backends(NULL);
+    while (list) {
+        const char *chr_name = list->value->name;
+
+        if (!strncmp(chr_name, str, len)) {
+            readline_add_completion(rs, chr_name);
+        }
+        list = list->next;
+    }
+    qapi_free_ChardevBackendInfoList(start);
+}
+
 void device_add_completion(ReadLineState *rs, int nb_args, const char *str)
 {
     GSList *list, *elt;