Add explanation to VHAL_HEARTBEAT property
Bug: 168132371
Test: build okay
Change-Id: I0755779b09ba830fae9f4017306740ec05b2f949
diff --git a/automotive/vehicle/2.0/types.hal b/automotive/vehicle/2.0/types.hal
index b7c72e4..d8a6838 100644
--- a/automotive/vehicle/2.0/types.hal
+++ b/automotive/vehicle/2.0/types.hal
@@ -2924,11 +2924,14 @@
| VehicleArea:GLOBAL),
/**
- * Defines an event that VHAL signals to the car watchdog as a heartbeat.
+ * Defines an event that VHAL signals to car watchdog as a heartbeat.
*
- * VHAL is supposed to write system uptime to this property at every 3 second.
- * Car watchdog subscribes to this property and checks if the property is updated at every 3
- * second. If it isn’t, car watchdog considers VHAL unhealthy and terminates it.
+ * If VHAL supports this property, VHAL should write system uptime to this property at every 3
+ * second. Car watchdog subscribes to this property and checks if the property is updated at
+ * every 3 second. With the buffer time of 3 second, car watchdog waits for a heart beat to be
+ * signaled up to 6 seconds from the last heart beat. If it isn’t, car watchdog considers
+ * VHAL unhealthy and terminates it.
+ * If this property is not supported by VHAL, car watchdog doesn't check VHAL health status.
*
* @change_mode VehiclePropertyChangeMode:ON_CHANGE
* @access VehiclePropertyAccess:READ