add and activate circuit breaker for gps failure detection

src/modules/commander/commander.cpp

@@ -1417,8 +1417,9 @@ int commander_thread_main(int argc, char *argv[])
 		}
 
 		/* check if GPS fix is ok */
-		if (gps_position.fix_type >= 3 && //XXX check eph and epv ?
+		if (circuit_breaker_enabled("CBRK_GPSFAIL", CBRK_GPSFAIL_KEY) ||
-			hrt_elapsed_time(&gps_position.timestamp_position) < FAILSAFE_DEFAULT_TIMEOUT) {
+				(gps_position.fix_type >= 3 &&
+				hrt_elapsed_time(&gps_position.timestamp_position) < FAILSAFE_DEFAULT_TIMEOUT)) {
 			/* handle the case where gps was regained */
 			if (status.gps_failure) {
 				status.gps_failure = false;

src/modules/systemlib/circuit_breaker.c

@@ -122,6 +122,20 @@ PARAM_DEFINE_INT32(CBRK_FLIGHTTERM, 121212);
  */
 PARAM_DEFINE_INT32(CBRK_ENGINEFAIL, 284953);
 
+/**
+ * Circuit breaker for gps failure detection
+ *
+ * Setting this parameter to 240024 will disable the gps failure detection.
+ * If the aircraft is in gps failure mode the gps failure flag will be
+ * set to healthy
+ * WARNING: ENABLING THIS CIRCUIT BREAKER IS AT OWN RISK
+ *
+ * @min 0
+ * @max 240024
+ * @group Circuit Breaker
+ */
+PARAM_DEFINE_INT32(CBRK_GPSFAIL, 240024);
+
 bool circuit_breaker_enabled(const char* breaker, int32_t magic)
 {
 	int32_t val;

src/modules/systemlib/circuit_breaker.h

@@ -55,6 +55,7 @@
 #define CBRK_AIRSPD_CHK_KEY	162128
 #define CBRK_FLIGHTTERM_KEY	121212
 #define CBRK_ENGINEFAIL_KEY	284953
+#define CBRK_GPSFAIL_KEY	240024
 
 #include <stdbool.h>