bd: Added trim function to let filesystems give erase hints to FTLs

features/filesystem/bd/BlockDevice.h

@@ -96,6 +96,22 @@ public:
         return 0;
     }
 
+    /** Mark blocks as no longer in use
+     *
+     *  This function provides a hint to the underlying block device that a region of blocks
+     *  is no longer in use and may be erased without side effects. Erase must still be called
+     *  before programming, but trimming allows flash-translation-layers to schedule erases when
+     *  the device is not busy.
+     *
+     *  @param addr     Address of block to mark as unused
+     *  @param size     Size to mark as unused in bytes, must be a multiple of erase block size
+     *  @return         0 on success, negative error code on failure
+     */
+    virtual int trim(bd_addr_t addr, bd_size_t size)
+    {
+        return 0;
+    }
+
     /** Get the size of a readable block
      *
      *  @return         Size of a readable block in bytes