AP_AHRS: replace prearm_healthy with pre_arm_check

Also removes prearm_failure_reason

libraries/AP_AHRS/AP_AHRS.h

@@ -171,10 +171,8 @@ public:
     // Methods
     virtual void update(bool skip_ins_update=false) = 0;
 
-    // report any reason for why the backend is refusing to initialise
-    virtual const char *prearm_failure_reason(void) const {
-        return nullptr;
-    }
+    // returns false if we fail arming checks, in which case the buffer will be populated with a failure message
+    virtual bool pre_arm_check(char *failure_msg, uint8_t failure_msg_len) const = 0;
 
     // check all cores providing consistent attitudes for prearm checks
     virtual bool attitudes_consistent(char *failure_msg, const uint8_t failure_msg_len) const { return true; }
@@ -482,8 +480,6 @@ public:
     // is the AHRS subsystem healthy?
     virtual bool healthy(void) const = 0;
 
-    virtual bool prearm_healthy(void) const { return healthy(); }
-
     // true if the AHRS has completed initialisation
     virtual bool initialised(void) const {
         return true;

libraries/AP_AHRS/AP_AHRS_DCM.cpp

@@ -1142,3 +1142,12 @@ bool AP_AHRS_DCM::get_velocity_NED(Vector3f &vec) const
     return true;
 }
 
+// returns false if we fail arming checks, in which case the buffer will be populated with a failure message
+bool AP_AHRS_DCM::pre_arm_check(char *failure_msg, uint8_t failure_msg_len) const
+{
+    if (!healthy()) {
+        hal.util->snprintf(failure_msg, failure_msg_len, "Not healthy");
+        return false;
+    }
+    return true;
+}

libraries/AP_AHRS/AP_AHRS_DCM.h

@@ -120,6 +120,9 @@ public:
 
     bool get_velocity_NED(Vector3f &vec) const override;
 
+    // returns false if we fail arming checks, in which case the buffer will be populated with a failure message
+    bool pre_arm_check(char *failure_msg, uint8_t failure_msg_len) const override;
+
 private:
     float _ki;
     float _ki_yaw;

libraries/AP_AHRS/AP_AHRS_NavEKF.cpp

@@ -1344,34 +1344,42 @@ bool AP_AHRS_NavEKF::healthy(void) const
     return AP_AHRS_DCM::healthy();
 }
 
-bool AP_AHRS_NavEKF::prearm_healthy(void) const
+// returns false if we fail arming checks, in which case the buffer will be populated with a failure message
+bool AP_AHRS_NavEKF::pre_arm_check(char *failure_msg, uint8_t failure_msg_len) const
 {
-    bool prearm_health = false;
     switch (ekf_type()) {
 #if CONFIG_HAL_BOARD == HAL_BOARD_SITL
     case EKFType::SITL:
 #endif
     case EKFType::NONE:
-        prearm_health = true;
-        break;
+        if (!healthy()) {
+            hal.util->snprintf(failure_msg, failure_msg_len, "Not healthy");
+            return false;
+        }
+        return true;
 
 #if HAL_NAVEKF2_AVAILABLE
     case EKFType::TWO:
-        if (_ekf2_started && EKF2.all_cores_healthy()) {
-            prearm_health = true;
+        if (!_ekf2_started) {
+            hal.util->snprintf(failure_msg, failure_msg_len, "EKF2 not started");
+            return false;
         }
-        break;
+        return EKF2.pre_arm_check(failure_msg, failure_msg_len);
 #endif
 
 #if HAL_NAVEKF3_AVAILABLE
     case EKFType::THREE:
-        if (_ekf3_started && EKF3.all_cores_healthy()) {
-            prearm_health = true;
+        if (!_ekf3_started) {
+            hal.util->snprintf(failure_msg, failure_msg_len, "EKF3 not started");
+            return false;
         }
-        break;
+        return EKF3.pre_arm_check(failure_msg, failure_msg_len);
 #endif
     }
-   return prearm_health && healthy();
+
+    // if we get here then ekf type is invalid
+    hal.util->snprintf(failure_msg, failure_msg_len, "invalid EKF type");
+    return false;
 }
 
 void AP_AHRS_NavEKF::set_ekf_use(bool setting)
@@ -1617,32 +1625,6 @@ void AP_AHRS_NavEKF::getCorrectedDeltaVelocityNED(Vector3f& ret, float& dt) cons
     ret.z += GRAVITY_MSS*dt;
 }
 
-// report any reason for why the backend is refusing to initialise
-const char *AP_AHRS_NavEKF::prearm_failure_reason(void) const
-{
-    switch (ekf_type()) {
-    case EKFType::NONE:
-        return nullptr;
-
-#if HAL_NAVEKF2_AVAILABLE
-    case EKFType::TWO:
-        return EKF2.prearm_failure_reason();
-#endif
-
-#if HAL_NAVEKF3_AVAILABLE
-    case EKFType::THREE:
-        return EKF3.prearm_failure_reason();
-#endif
-
-#if CONFIG_HAL_BOARD == HAL_BOARD_SITL
-    case EKFType::SITL:
-        return nullptr;
-#endif
-    }
-
-    return nullptr;
-}
-
 // check all cores providing consistent attitudes for prearm checks
 bool AP_AHRS_NavEKF::attitudes_consistent(char *failure_msg, const uint8_t failure_msg_len) const
 {

libraries/AP_AHRS/AP_AHRS_NavEKF.h

@@ -200,7 +200,8 @@ public:
     // is the AHRS subsystem healthy?
     bool healthy() const override;
 
-    bool prearm_healthy() const override;
+    // returns false if we fail arming checks, in which case the buffer will be populated with a failure message
+    bool pre_arm_check(char *failure_msg, uint8_t failure_msg_len) const override;
 
     // true if the AHRS has completed initialisation
     bool initialised() const override;
@@ -212,9 +213,6 @@ public:
     // true if offsets are valid
     bool getMagOffsets(uint8_t mag_idx, Vector3f &magOffsets) const;
 
-    // report any reason for why the backend is refusing to initialise
-    const char *prearm_failure_reason(void) const override;
-
     // check all cores providing consistent attitudes for prearm checks
     bool attitudes_consistent(char *failure_msg, const uint8_t failure_msg_len) const override;