From ddcca7b1a899ce9dec620edcd58dbdbb98be1ba1 Mon Sep 17 00:00:00 2001
From: "Konstantin Sharlaimov (DigitalEntity)"
 <konstantin.sharlaimov@gmail.com>
Date: Wed, 20 Mar 2019 19:45:43 +0100
Subject: [PATCH] [BUS] Lazy allocate device scratchpad memory. Will only
 allocate it if driver accesses it.

---
 src/main/drivers/bus.c | 15 +++++++++++++--
 src/main/drivers/bus.h |  6 +++---
 2 files changed, 16 insertions(+), 5 deletions(-)

diff --git a/src/main/drivers/bus.c b/src/main/drivers/bus.c
index d1ec5de353..f97cdbc44c 100755
--- a/src/main/drivers/bus.c
+++ b/src/main/drivers/bus.c
@@ -27,6 +27,8 @@
 #include "platform.h"
 #include "build/debug.h"
 
+#include "common/memory.h"
+
 #include "drivers/bus.h"
 #include "drivers/io.h"
 
@@ -199,16 +201,25 @@ void busSetSpeed(const busDevice_t * dev, busSpeed_e speed)
 
 uint32_t busDeviceReadScratchpad(const busDevice_t * dev)
 {
-    return dev->scratchpad[0];
+    uint32_t * mem = busDeviceGetScratchpadMemory(dev);
+    return (mem != NULL) ? mem[0] : 0;
 }
 
 void busDeviceWriteScratchpad(busDevice_t * dev, uint32_t value)
 {
-    dev->scratchpad[0] = value;
+    uint32_t * mem = busDeviceGetScratchpadMemory(dev);
+
+    if (mem != NULL) {
+        mem[0] = value;
+    }
 }
 
 void * busDeviceGetScratchpadMemory(const busDevice_t * dev)
 {
+    if (dev->scratchpad == NULL) {
+        ((busDevice_t *)dev)->scratchpad = memAllocate(BUS_SCRATCHPAD_MEMORY_SIZE, OWNER_SYSTEM);
+    }
+
     return (void *)dev->scratchpad;
 }
 
diff --git a/src/main/drivers/bus.h b/src/main/drivers/bus.h
index 034be77364..489454aa6a 100755
--- a/src/main/drivers/bus.h
+++ b/src/main/drivers/bus.h
@@ -192,9 +192,9 @@ typedef struct busDevice_s {
 #endif
     } busdev;
     IO_t irqPin;                    // Device IRQ pin. Bus system will only assign IO_t object to this var. Initialization is up to device driver
-    uint32_t scratchpad[BUS_SCRATCHPAD_MEMORY_SIZE / sizeof(uint32_t)];     // Memory where device driver can store persistent data. Zeroed out when initializing the device
-                                                                            // for the first time. Useful when once device is shared between several sensors
-                                                                            // (like MPU/ICM acc-gyro sensors)
+    uint32_t * scratchpad;          // Memory where device driver can store persistent data. Zeroed out when initializing the device
+                                    // for the first time. Useful when once device is shared between several sensors
+                                    // (like MPU/ICM acc-gyro sensors)
 } busDevice_t;
 
 #ifdef __APPLE__