system_params: add SYS_HAS_MAG and SYS_HAS_BARO params

This allows to use PX4 on systems that do not have a mag or a baro,
such as the Omnibus F4 SD.

src/modules/commander/PreflightCheck.cpp

@@ -712,12 +712,14 @@ bool preflightCheck(orb_advert_t *mavlink_log_pub, const vehicle_status_s &statu
 		bool prime_found = false;
 		int32_t prime_id = 0;
 		param_get(param_find("CAL_MAG_PRIME"), &prime_id);
+		int32_t sys_has_mag = 1;
+		param_get(param_find("SYS_HAS_MAG"), &sys_has_mag);
 
 		bool mag_fail_reported = false;
 
 		/* check all sensors, but fail only for mandatory ones */
 		for (unsigned i = 0; i < max_optional_mag_count; i++) {
-			bool required = (i < max_mandatory_mag_count);
+			bool required = (i < max_mandatory_mag_count) && sys_has_mag == 1;
 			int device_id = -1;
 
 			if (!magnometerCheck(mavlink_log_pub, i, !required, device_id, (reportFailures && !failed && !mag_fail_reported)) && required) {
@@ -816,12 +818,14 @@ bool preflightCheck(orb_advert_t *mavlink_log_pub, const vehicle_status_s &statu
 		bool prime_found = false;
 		int32_t prime_id = 0;
 		param_get(param_find("CAL_BARO_PRIME"), &prime_id);
+		int32_t sys_has_baro = 1;
+		param_get(param_find("SYS_HAS_BARO"), &sys_has_baro);
 
 		bool baro_fail_reported = false;
 
 		/* check all sensors, but fail only for mandatory ones */
 		for (unsigned i = 0; i < max_optional_baro_count; i++) {
-			bool required = (i < max_mandatory_baro_count);
+			bool required = (i < max_mandatory_baro_count) && sys_has_baro == 1;
 			int device_id = -1;
 
 			if (!baroCheck(mavlink_log_pub, i, !required, device_id, (reportFailures && !failed && !baro_fail_reported)) && required) {

src/modules/sensors/parameters.cpp

@@ -188,6 +188,9 @@ void initialize_parameter_handles(ParameterHandles &parameter_handles)
 	(void)param_find("SYS_CAL_TDEL");
 	(void)param_find("SYS_CAL_TMAX");
 	(void)param_find("SYS_CAL_TMIN");
+
+	(void)param_find("SYS_HAS_MAG");
+	(void)param_find("SYS_HAS_BARO");
 }
 
 int update_parameters(const ParameterHandles &parameter_handles, Parameters &parameters)

src/modules/systemlib/system_params.c

@@ -248,3 +248,32 @@ PARAM_DEFINE_INT32(SYS_CAL_TMIN, 5);
  * @group System
  */
 PARAM_DEFINE_INT32(SYS_CAL_TMAX, 10);
+
+/**
+ * Control if the vehicle has a magnetometer
+ *
+ * Disable this if the board has no magnetometer, such as the Omnibus F4 SD.
+ * If disabled, the preflight checks will not check for the presence of a
+ * magnetometer.
+ *
+ * @boolean
+ * @reboot_required true
+ *
+ * @group System
+ */
+PARAM_DEFINE_INT32(SYS_HAS_MAG, 1);
+
+/**
+ * Control if the vehicle has a barometer
+ *
+ * Disable this if the board has no barometer, such as some of the the Omnibus
+ * F4 SD variants.
+ * If disabled, the preflight checks will not check for the presence of a
+ * barometer.
+ *
+ * @boolean
+ * @reboot_required true
+ *
+ * @group System
+ */
+PARAM_DEFINE_INT32(SYS_HAS_BARO, 1);