QMP: Introduce RTC_CHANGE event

Emitted whenever the RTC time changes.
Signed-off-by: NLuiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: NAnthony Liguori <aliguori@us.ibm.com>

QMP/qmp-events.txt

@@ -38,6 +38,21 @@ Example:
 { "event": "RESET",
     "timestamp": { "seconds": 1267041653, "microseconds": 9518 } }
 
+RTC_CHANGE
+----------
+
+Emitted when the RTC time changes.
+
+Data:
+
+- "offset": delta against the host UTC in seconds (json-number)
+
+Example:
+
+{ "event": "RTC_CHANGE",
+    "data": { "offset": 78 },
+    "timestamp": { "seconds": 1267020223, "microseconds": 435656 } }
+
 SHUTDOWN
 --------
 

hw/mc146818rtc.c

@@ -297,6 +297,8 @@ static void rtc_set_time(RTCState *s)
     tm->tm_mday = rtc_from_bcd(s, s->cmos_data[RTC_DAY_OF_MONTH]);
     tm->tm_mon = rtc_from_bcd(s, s->cmos_data[RTC_MONTH]) - 1;
     tm->tm_year = rtc_from_bcd(s, s->cmos_data[RTC_YEAR]) + s->base_year - 1900;
+
+    rtc_change_mon_event(tm);
 }
 
 static void rtc_copy_date(RTCState *s)

monitor.c

@@ -423,6 +423,9 @@ void monitor_protocol_event(MonitorEvent event, QObject *data)
         case QEVENT_BLOCK_IO_ERROR:
             event_name = "BLOCK_IO_ERROR";
             break;
+        case QEVENT_RTC_CHANGE:
+            event_name = "RTC_CHANGE";
+            break;
         default:
             abort();
             break;

monitor.h

@@ -23,6 +23,7 @@ typedef enum MonitorEvent {
     QEVENT_VNC_INITIALIZED,
     QEVENT_VNC_DISCONNECTED,
     QEVENT_BLOCK_IO_ERROR,
+    QEVENT_RTC_CHANGE,
     QEVENT_MAX,
 } MonitorEvent;
 

sysemu.h

@@ -256,6 +256,8 @@ void do_usb_add(Monitor *mon, const QDict *qdict);
 void do_usb_del(Monitor *mon, const QDict *qdict);
 void usb_info(Monitor *mon);
 
+void rtc_change_mon_event(struct tm *tm);
+
 void register_devices(void);
 
 #endif

vl.c

@@ -1492,6 +1492,15 @@ int qemu_timedate_diff(struct tm *tm)
     return seconds - time(NULL);
 }
 
+void rtc_change_mon_event(struct tm *tm)
+{
+    QObject *data;
+
+    data = qobject_from_jsonf("{ 'offset': %d }", qemu_timedate_diff(tm));
+    monitor_protocol_event(QEVENT_RTC_CHANGE, data);
+    qobject_decref(data);
+}
+
 static void configure_rtc_date_offset(const char *startdate, int legacy)
 {
     time_t rtc_start_date;