From 97b5b0448ac48aa2862e3d19bd08079d2bf43fa9 Mon Sep 17 00:00:00 2001
From: Andy Piper <github@andypiper.com>
Date: Tue, 12 May 2026 12:02:39 +0100
Subject: [PATCH] AP_DAL: move gyro bias metadata to new RISJ message

These fields are constant per-instance, so logging them in RISI
inflated the replay log on every frame and broke replay of logs
captured before this PR landed (RISI gained two floats).

Restore RISI to its original layout and add RISJ, which carries
gyro_bias_limit and gyro_bias_init_dps plus the instance and is
written only when changed via WRITE_REPLAY_BLOCK_IFCHANGED.

Seed _RISJ[] with the legacy defaults (0.5 rad/s clamp,
2.5 deg/s init) in the DAL constructor so replays of older logs
that have no RISJ messages still feed sane values to the EKF.
---
 libraries/AP_DAL/AP_DAL.h                  |  3 +++
 libraries/AP_DAL/AP_DAL_InertialSensor.cpp | 19 +++++++++++++++----
 libraries/AP_DAL/AP_DAL_InertialSensor.h   |  8 ++++++--
 libraries/AP_DAL/LogStructure.h            | 21 ++++++++++++++++-----
 4 files changed, 40 insertions(+), 11 deletions(-)

diff --git a/libraries/AP_DAL/AP_DAL.h b/libraries/AP_DAL/AP_DAL.h
index 4ae6cf264ec..553c16b3164 100644
--- a/libraries/AP_DAL/AP_DAL.h
+++ b/libraries/AP_DAL/AP_DAL.h
@@ -270,6 +270,9 @@ public:
     void handle_message(const log_RISI &msg) {
         _ins.handle_message(msg);
     }
+    void handle_message(const log_RISJ &msg) {
+        _ins.handle_message(msg);
+    }
 
     void handle_message(const log_RASH &msg) {
         if (_airspeed == nullptr) {
diff --git a/libraries/AP_DAL/AP_DAL_InertialSensor.cpp b/libraries/AP_DAL/AP_DAL_InertialSensor.cpp
index 5e3bbe15bdf..5a60f4799a9 100644
--- a/libraries/AP_DAL/AP_DAL_InertialSensor.cpp
+++ b/libraries/AP_DAL/AP_DAL_InertialSensor.cpp
@@ -8,7 +8,13 @@ AP_DAL_InertialSensor::AP_DAL_InertialSensor()
     for (uint8_t i=0; i<ARRAY_SIZE(_RISI); i++) {
         _RISI[i].instance = i;
     }
-
+    // seed RISJ with legacy defaults so replay of older logs (with no
+    // RISJ messages) still gives the EKF sane gyro bias clamp/init values.
+    for (uint8_t i=0; i<ARRAY_SIZE(_RISJ); i++) {
+        _RISJ[i].instance = i;
+        _RISJ[i].gyro_bias_limit = 0.5f;
+        _RISJ[i].gyro_bias_init_dps = 2.5f;
+    }
 }
 
 void AP_DAL_InertialSensor::start_frame()
@@ -41,13 +47,18 @@ void AP_DAL_InertialSensor::start_frame()
             RISI.get_delta_angle_ret = ins.get_delta_angle(i, RISI.delta_angle, RISI.delta_angle_dt);
         }
 
-        RISI.gyro_bias_limit = ins.get_gyro_bias_limit_rads(i);
-        RISI.gyro_bias_init_dps = ins.get_gyro_bias_init_dps(i);
-
         update_filtered(i);
 
         WRITE_REPLAY_BLOCK_IFCHANGED(RISI, RISI, old_RISI);
 
+        // RISJ holds per-instance gyro bias metadata. These are constants
+        // set by the backend, so the message is only written when changed.
+        log_RISJ &RISJ = _RISJ[i];
+        const log_RISJ old_RISJ = RISJ;
+        RISJ.gyro_bias_limit = ins.get_gyro_bias_limit_rads(i);
+        RISJ.gyro_bias_init_dps = ins.get_gyro_bias_init_dps(i);
+        WRITE_REPLAY_BLOCK_IFCHANGED(RISJ, RISJ, old_RISJ);
+
         // update sensor position
         pos[i] = ins.get_imu_pos_offset(i);
     }
diff --git a/libraries/AP_DAL/AP_DAL_InertialSensor.h b/libraries/AP_DAL/AP_DAL_InertialSensor.h
index a1458d8e408..0eb0f3e47b3 100644
--- a/libraries/AP_DAL/AP_DAL_InertialSensor.h
+++ b/libraries/AP_DAL/AP_DAL_InertialSensor.h
@@ -33,8 +33,8 @@ public:
     uint8_t get_first_usable_gyro(void) const { return _RISH.first_usable_gyro; };
 
     bool use_gyro(uint8_t instance) const { return _RISI[instance].use_gyro; }
-    float get_gyro_bias_limit(uint8_t instance) const { return _RISI[instance].gyro_bias_limit; }
-    float get_gyro_bias_init_dps(uint8_t instance) const { return _RISI[instance].gyro_bias_init_dps; }
+    float get_gyro_bias_limit(uint8_t instance) const { return _RISJ[instance].gyro_bias_limit; }
+    float get_gyro_bias_init_dps(uint8_t instance) const { return _RISJ[instance].gyro_bias_init_dps; }
     const Vector3f     &get_gyro(uint8_t i) const { return gyro_filtered[i]; }
     const Vector3f     &get_gyro() const { return get_gyro(_primary_gyro); }
     bool get_delta_angle(uint8_t i, Vector3f &delta_angle, float &delta_angle_dt) const {
@@ -59,10 +59,14 @@ public:
         pos[msg.instance] = AP::ins().get_imu_pos_offset(msg.instance);
         update_filtered(msg.instance);
     }
+    void handle_message(const log_RISJ &msg) {
+        _RISJ[msg.instance] = msg;
+    }
 
 private:
     struct log_RISH _RISH;
     struct log_RISI _RISI[INS_MAX_INSTANCES];
+    struct log_RISJ _RISJ[INS_MAX_INSTANCES];
     float alpha;
 
     // sensor positions
diff --git a/libraries/AP_DAL/LogStructure.h b/libraries/AP_DAL/LogStructure.h
index 169909a18ca..a7824544d85 100644
--- a/libraries/AP_DAL/LogStructure.h
+++ b/libraries/AP_DAL/LogStructure.h
@@ -19,6 +19,7 @@
     LOG_RFRN_MSG, \
     LOG_RISH_MSG, \
     LOG_RISI_MSG, \
+    LOG_RISJ_MSG, \
     LOG_RBRH_MSG, \
     LOG_RBRI_MSG, \
     LOG_RRNH_MSG, \
@@ -125,8 +126,6 @@ struct log_RISH {
 // @Field: DAZ: z-axis delta-angle
 // @Field: DVDT: delta-velocity-delta-time
 // @Field: DADT: delta-angle-delta-time
-// @Field: GBL: gyro bias limit (rad/s) for the EKF gyro bias state clamp
-// @Field: GBI: initial gyro bias 1-sigma uncertainty (deg/s)
 // @Field: Flags: use-accel, use-gyro, delta-vel-valid, delta-accel-valid
 // @Field: I: IMU instance
 struct log_RISI {
@@ -134,8 +133,6 @@ struct log_RISI {
     Vector3f delta_angle;
     float delta_velocity_dt;
     float delta_angle_dt;
-    float gyro_bias_limit;
-    float gyro_bias_init_dps;
     uint8_t use_accel:1;
     uint8_t use_gyro:1;
     uint8_t get_delta_velocity_ret:1;
@@ -144,6 +141,18 @@ struct log_RISI {
     uint8_t _end;
 };
 
+// @LoggerMessage: RISJ
+// @Description: Replay Inertial Sensor instance metadata (low-rate, only logged when changed)
+// @Field: GBL: gyro bias limit (rad/s) for the EKF gyro bias state clamp
+// @Field: GBI: initial gyro bias 1-sigma uncertainty (deg/s)
+// @Field: I: IMU instance
+struct log_RISJ {
+    float gyro_bias_limit;
+    float gyro_bias_init_dps;
+    uint8_t instance;
+    uint8_t _end;
+};
+
 // @LoggerMessage: REV2
 // @Description: Replay Event (EKF2)
 // @Field: Event: external event injected into EKF
@@ -619,7 +628,9 @@ struct log_RTER {
     { LOG_RISH_MSG, RLOG_SIZE(RISH),                                   \
       "RISH", "HBBfBB", "LR,PG,PA,LD,AC,GC", "------", "------" }, \
     { LOG_RISI_MSG, RLOG_SIZE(RISI),                                   \
-      "RISI", "ffffffffffBB", "DVX,DVY,DVZ,DAX,DAY,DAZ,DVDT,DADT,GBL,GBI,Flags,I", "-----------#", "------------" }, \
+      "RISI", "ffffffffBB", "DVX,DVY,DVZ,DAX,DAY,DAZ,DVDT,DADT,Flags,I", "---------#", "----------" }, \
+    { LOG_RISJ_MSG, RLOG_SIZE(RISJ),                                   \
+      "RISJ", "ffB", "GBL,GBI,I", "--#", "---" }, \
     { LOG_RASH_MSG, RLOG_SIZE(RASH),                                   \
       "RASH", "BB", "Primary,NumInst", "--", "--" },  \
     { LOG_RASI_MSG, RLOG_SIZE(RASI),                                   \