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docs/design-documents/features/storage/BlockDevices/get_type_method.md

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+# Get type method addon to block devices class
+ 
+### Revision history
+| Revision  | Date            | Authors                                                     | Mbed OS version        | Comments         |
+|---------- |-----------------|-------------------------------------------------------------|------------------------|------------------|
+| 1.0       | 04/12/2018      | Yossi Levy ([@yossi2le](https://github.com/yossi2le/))      | 5.11+                  | Initial revision |
+ 
+## Introduction
+ 
+Most storage solutions use block devices, whether it is Filesystems, KVStore or any other solution 
+most of them will have some BlockDevice class underneath. However, sometimes a storage type or an application needs to know the physical 
+BlockDevice type in order to work smoothly or the BlockDevice type in order to decide what is
+the best storage configuration to use.
+To address this an add-on method of getting type is proposed for BlockDevice interface class.
+ 
+## The Motivation 
+ 
+Below there is a list of some examples to explain the motivation and the need for the adding of get_type to BlockDevice interface.
+ 
+examples:
+- TDBStore needs to know if there are flash characteristics for the block device and if there aren<65>t it should use
+  FlashSimBlockDevice to simulate a flash BlockDevice.
+- When creating a file system you would prefer working with FAT on top of SD while LITTLEFS on top of any flash block device. 
+  Those preference in favor of better performance.
+
+To summarize the above, it may be very useful when using block device to know the type of the instance and especially, but not only, 
+when using get_default_instace. Sometimes applications and tests would like to behave differently depending on the instance that has been created
+or provided to them.
+ 
+In fact it might be worth to consider adding the get_type to any interface with get_default_instance at mbed-os.   
+  
+## Dive into details
+we should add the following method to BlockDevice interface class.
+ 
+```virtual const char * get_type() const = 0;```
+ 
+then every physical BlockDevice class which implements the interface should also implement this method and return a string 
+representing its type. Furthermore, a nonphysical BlockDevice like SlicingBlockDevice should return the underlying physical 
+BlockDevice type.
+ 
+### Physical BlockDevice:
+```
+const char * HeapBlockDevice::get_type() const
+{
+    return "HEAP";
+}
+```
+ 
+### Logical BlockDevice:
+```
+const char * SlicingBlockDevice::get_type() const
+{
+    if (_bd != NULL) {
+     return _bd->get_type();
+    }
+ 
+    return NULL;
+}
+```
+
+### Open issue
+The ChainingBlockDevice which chains different type of physical block devices into one block device is unable
+to return the underneath physical as it contains two or more types. Therefore it will return CHAINING as its 
+identity and its left for the user to decide how the application will treat this information.
+
+
+The below table describes physical BlockDevice and its tyep names
+
+
+| BlockDevice class           | String description | 
+|-----------------------------|--------------------|
+| HeapBlockDevice             | "HEAP"             |
+| SPIFBlockDevice             | "SPIF"             |
+| QSPIFBlockDevice            | "QSPIF"            |
+| SDBlockDevice               | "SD"               |
+| FlashIAPBlockDevice         | "FLASHIAP"         |
+| DataFlashBlockDevice        | "DATAFLASH"        |
+| ChainingBlockDevice         | "CHAINING"         |