transport: dbus: Implement flush

Change-Id: If34f2f6cac002fae417d99baec8c08f675cdb974
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/transport_dbus.c b/transport_dbus.c
index 044e8dc..e04db67 100644
--- a/transport_dbus.c
+++ b/transport_dbus.c
@@ -341,6 +341,32 @@
 	return sd_bus_send(NULL, n, NULL);
 }
 
+static int transport_dbus_write_flush(sd_bus_message *m, void *userdata,
+				      sd_bus_error *ret_error)
+{
+	struct mbox_context *context = userdata;
+	sd_bus_message *n;
+	int rc;
+
+	if (!context) {
+		MSG_ERR("DBUS Internal Error\n");
+		return -EINVAL;
+	}
+
+	rc = context->protocol->flush(context, NULL /* No args in v2 */);
+	if (rc < 0) {
+		return rc;
+	}
+
+	rc = sd_bus_message_new_method_return(m, &n);
+	if (rc < 0) {
+		MSG_ERR("sd_bus_message_new_method_return failed: %d\n", rc);
+		return rc;
+	}
+
+	return sd_bus_send(NULL, n, NULL);
+}
+
 static int transport_dbus_ack(sd_bus_message *m, void *userdata,
 			      sd_bus_error *ret_error)
 {
@@ -430,6 +456,8 @@
 		      SD_BUS_VTABLE_UNPRIVILEGED),
 	SD_BUS_METHOD("MarkDirty", "qq", NULL, &transport_dbus_mark_dirty,
 		      SD_BUS_VTABLE_UNPRIVILEGED),
+	SD_BUS_METHOD("Flush", NULL, NULL, &transport_dbus_write_flush,
+		      SD_BUS_VTABLE_UNPRIVILEGED),
 	SD_BUS_METHOD("Ack", "y", NULL, &transport_dbus_ack,
 		      SD_BUS_VTABLE_UNPRIVILEGED),
 	SD_BUS_PROPERTY("FlashControlLost", "b", transport_dbus_get_property,