From 8747ae539f405071ce08a2a3faac6adeaf2e1160 Mon Sep 17 00:00:00 2001
From: Thomas Watson <twatson52@icloud.com>
Date: Mon, 20 Nov 2023 20:04:06 -0600
Subject: [PATCH] AP_HAL: move serial re-mapping to driver array initialization

Saves a bit of flash and execution time.
---
 libraries/AP_HAL/HAL.cpp | 7 ++-----
 libraries/AP_HAL/HAL.h   | 9 +++++----
 2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/libraries/AP_HAL/HAL.cpp b/libraries/AP_HAL/HAL.cpp
index 1cd4d5b367..deef2581c3 100644
--- a/libraries/AP_HAL/HAL.cpp
+++ b/libraries/AP_HAL/HAL.cpp
@@ -15,11 +15,8 @@ HAL::FunCallbacks::FunCallbacks(void (*setup_fun)(void), void (*loop_fun)(void))
 // access serial ports using SERIALn numbering
 AP_HAL::UARTDriver* AP_HAL::HAL::serial(uint8_t sernum) const
 {
-    // this mapping captures the historical use of uartB as SERIAL3
-    const uint8_t mapping[] = { 0, 2, 3, 1, 4, 5, 6, 7, 8, 9 };
-    static_assert(sizeof(mapping) == ARRAY_SIZE(uart_array), "array size must match mapping");
-    if (sernum >= ARRAY_SIZE(uart_array)) {
+    if (sernum >= ARRAY_SIZE(serial_array)) {
         return nullptr;
     }
-    return uart_array[mapping[sernum]];
+    return serial_array[sernum];
 }
diff --git a/libraries/AP_HAL/HAL.h b/libraries/AP_HAL/HAL.h
index 0695504fb5..d56aeaa724 100644
--- a/libraries/AP_HAL/HAL.h
+++ b/libraries/AP_HAL/HAL.h
@@ -53,11 +53,11 @@ public:
         AP_HAL::CANIface** _can_ifaces)
 #endif
         :
-        uart_array{
+        serial_array{
             _uartA,
-            _uartB,
-            _uartC,
+            _uartC, // ordering captures the historical use of uartB as SERIAL3
             _uartD,
+            _uartB,
             _uartE,
             _uartF,
             _uartG,
@@ -140,7 +140,8 @@ public:
     static constexpr uint8_t num_serial = 10;
 
 private:
-    AP_HAL::UARTDriver* uart_array[num_serial];
+    // UART drivers in SERIALn_ order
+    AP_HAL::UARTDriver* serial_array[num_serial];
 
 public:
 #if AP_SIM_ENABLED && CONFIG_HAL_BOARD != HAL_BOARD_SITL