Updated code to match new secondary_bd API

Author: AGlass0fMilk

README.md

@@ -37,6 +37,8 @@ By default, the secondary memory region is provided by the `mbed::BlockDevice::g
 mbed::BlockDevice* get_secondary_bd(void);
 ```
 
+See the example file in this repository, `default_bd.cpp`.
+
 Since the Mbed-OS mcuboot port uses Mbed's `BlockDevice` API, there is a lot of flexibility when providing the secondary memory region. For example, you can use a `FlashIAPBlockDevice` if your application is small enough to fit two copies in the internal flash. If you also use your external flash chip for data storage you can simply wrap the whole `BlockDevice` object in a `SlicingBlockDevice` to give mcuboot access to a certain region of your external flash.
 
 The Mbed-OS mcuboot port also has an additional function that the application can define if needed: `void mbed_mcuboot_user_init(void)`. This is provided as a `weak` symbol so the application can perform any necessary initialization before the rest of the boot process begins.

default_bd.cpp

@@ -68,3 +68,11 @@ BlockDevice *BlockDevice::get_default_instance()
 
 }
 
+/**
+ * You can override this function to suit your hardware/memory configuration
+ * By default it simply returns what is returned by BlockDevice::get_default_instance();
+ */
+//mbed::BlockDevice* get_secondary_bd(void) {
+//    return mbed::BlockDevice::get_default_instance();
+//}
+

user_main.cpp

@@ -23,15 +23,8 @@ using namespace std::chrono;
 
 #endif // MBED_CONF_APP_SERIAL_BOOTLOADER_ENABLE
 
-mbed::BlockDevice* mcuboot_secondary_bd;
-
 void mbed_mcuboot_user_init(void) {
 
-    mbed::BlockDevice* mcuboot_secondary_bd = mbed::BlockDevice::get_default_instance();
-
-    // Initialize the secondary/update candidate block device
-    mcuboot_secondary_bd->init();
-
 #if MBED_CONF_APP_SERIAL_BOOTLOADER_ENABLE
 
     // Set up the serial bootloader