trace: Allow event name pattern in "info trace-events"

Homogenizes the command capabilities with QMP.
Signed-off-by: NLluís Vilanova <vilanova@ac.upc.edu>
Reviewed-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>

hmp-commands-info.hx

@@ -646,10 +646,12 @@ ETEXI
 
     {
         .name       = "trace-events",
-        .args_type  = "",
-        .params     = "",
-        .help       = "show available trace-events & their state",
+        .args_type  = "name:s?",
+        .params     = "[name]",
+        .help       = "show available trace-events & their state "
+                      "(name: event name pattern)",
         .mhandler.cmd = hmp_info_trace_events,
+        .command_completion = info_trace_events_completion,
     },
 
 STEXI

hmp.h

@@ -115,6 +115,7 @@ void set_link_completion(ReadLineState *rs, int nb_args, const char *str);
 void netdev_add_completion(ReadLineState *rs, int nb_args, const char *str);
 void netdev_del_completion(ReadLineState *rs, int nb_args, const char *str);
 void ringbuf_write_completion(ReadLineState *rs, int nb_args, const char *str);
+void info_trace_events_completion(ReadLineState *rs, int nb_args, const char *str);
 void trace_event_completion(ReadLineState *rs, int nb_args, const char *str);
 void watchdog_action_completion(ReadLineState *rs, int nb_args,
                                 const char *str);

monitor.c

@@ -1065,8 +1065,20 @@ static void hmp_info_cpustats(Monitor *mon, const QDict *qdict)
 
 static void hmp_info_trace_events(Monitor *mon, const QDict *qdict)
 {
-    TraceEventInfoList *events = qmp_trace_event_get_state("*", NULL);
+    const char *name = qdict_get_try_str(qdict, "name");
+    TraceEventInfoList *events;
     TraceEventInfoList *elem;
+    Error *local_err = NULL;
+
+    if (name == NULL) {
+        name = "*";
+    }
+
+    events = qmp_trace_event_get_state(name, &local_err);
+    if (local_err) {
+        error_report_err(local_err);
+        return;
+    }
 
     for (elem = events; elem != NULL; elem = elem->next) {
         monitor_printf(mon, "%s : state %u\n",
@@ -3296,6 +3308,23 @@ void netdev_del_completion(ReadLineState *rs, int nb_args, const char *str)
     }
 }
 
+void info_trace_events_completion(ReadLineState *rs, int nb_args, const char *str)
+{
+    size_t len;
+
+    len = strlen(str);
+    readline_set_completion_index(rs, len);
+    if (nb_args == 2) {
+        TraceEventID id;
+        for (id = 0; id < trace_event_count(); id++) {
+            const char *event_name = trace_event_get_name(trace_event_id(id));
+            if (!strncmp(str, event_name, len)) {
+                readline_add_completion(rs, event_name);
+            }
+        }
+    }
+}
+
 void trace_event_completion(ReadLineState *rs, int nb_args, const char *str)
 {
     size_t len;