From 42805aa89246e897ba487926d9f3731f39c8f6f3 Mon Sep 17 00:00:00 2001
From: Peter Barker <pbarker@barker.dropbear.id.au>
Date: Fri, 28 Jun 2024 13:10:32 +1000
Subject: [PATCH] AP_GPS: confine inter-instance DroneCAN state checks to
 DroneCAN GPSs

stop these looking at parameters/state for all GPSs, focus on DroneCAN GPSs
---
 libraries/AP_GPS/AP_GPS_DroneCAN.cpp | 23 ++++++++---------------
 libraries/AP_GPS/AP_GPS_DroneCAN.h   |  9 +++++++++
 2 files changed, 17 insertions(+), 15 deletions(-)

diff --git a/libraries/AP_GPS/AP_GPS_DroneCAN.cpp b/libraries/AP_GPS/AP_GPS_DroneCAN.cpp
index a011e69c69..8bd8cb7e37 100644
--- a/libraries/AP_GPS/AP_GPS_DroneCAN.cpp
+++ b/libraries/AP_GPS/AP_GPS_DroneCAN.cpp
@@ -227,24 +227,13 @@ AP_GPS_Backend* AP_GPS_DroneCAN::probe(AP_GPS &_gps, AP_GPS::GPS_State &_state)
 
 bool AP_GPS_DroneCAN::inter_instance_pre_arm_checks(char failure_msg[], uint16_t failure_msg_len)
 {
-    // only do these checks if there is at least one DroneCAN GPS:
-    bool found_uavan_type = false;
-    for (uint8_t i = 0; i < GPS_MAX_RECEIVERS; i++) {
-        const auto type = AP::gps().params[i].type;
-        if (type != AP_GPS::GPS_TYPE_UAVCAN &&
-            type != AP_GPS::GPS_TYPE_UAVCAN_RTK_BASE &&
-            type != AP_GPS::GPS_TYPE_UAVCAN_RTK_ROVER) {
-            continue;
-        }
-        found_uavan_type = true;
-   }
-    if (!found_uavan_type) {
-        return true;
-    }
-
     // lint parameters and detected node IDs:
     for (uint8_t i = 0; i < GPS_MAX_RECEIVERS; i++) {
         const auto &params_i = AP::gps().params[i];
+        // we are only interested in parameters for DroneCAN GPSs:
+        if (!is_dronecan_gps_type(params_i.type)) {
+            continue;
+        }
         bool overriden_node_found = false;
         bool bad_override_config = false;
         if (params_i.override_node_id == 0) {
@@ -253,6 +242,10 @@ bool AP_GPS_DroneCAN::inter_instance_pre_arm_checks(char failure_msg[], uint16_t
         }
         for (uint8_t j = 0; j < GPS_MAX_RECEIVERS; j++) {
             const auto &params_j = AP::gps().params[j];
+            // we are only interested in parameters for DroneCAN GPSs:
+            if (!is_dronecan_gps_type(params_j.type)) {
+                continue;
+            }
             if (params_i.override_node_id == params_j.override_node_id && (i != j)) {
                 bad_override_config = true;
                 break;
diff --git a/libraries/AP_GPS/AP_GPS_DroneCAN.h b/libraries/AP_GPS/AP_GPS_DroneCAN.h
index f422c983fe..1de0b6b8f4 100644
--- a/libraries/AP_GPS/AP_GPS_DroneCAN.h
+++ b/libraries/AP_GPS/AP_GPS_DroneCAN.h
@@ -149,6 +149,15 @@ private:
         uint32_t last_send_ms;
         ByteBuffer *buf;
     } _rtcm_stream;
+
+    // returns true if the supplied GPS_Type is a DroneCAN GPS type
+    static bool is_dronecan_gps_type(AP_GPS::GPS_Type type) {
+        return (
+            type == AP_GPS::GPS_TYPE_UAVCAN ||
+            type == AP_GPS::GPS_TYPE_UAVCAN_RTK_BASE ||
+            type == AP_GPS::GPS_TYPE_UAVCAN_RTK_ROVER
+       );
+    }
 };
 
 #endif  // AP_GPS_DRONECAN_ENABLED