fix includes and add some comments

src/fw-update/fw-update-device-interface.h

@@ -1,12 +1,12 @@
 // License: Apache 2.0. See LICENSE file in root directory.
-// Copyright(c) 2019 Intel Corporation. All Rights Reserved.
-
+// Copyright(c) 2023 Intel Corporation. All Rights Reserved.
 #pragma once
 
-#include "../types.h"
 #include <src/core/device-interface.h>
-#include "../usb/usb-types.h"
-#include <cstddef>
+#include <librealsense2/hpp/rs_types.hpp>
+#include <cstdint>
+#include <vector>
+
 
 namespace librealsense
 {
@@ -16,20 +16,33 @@ namespace librealsense
         virtual bool check_fw_compatibility(const std::vector<uint8_t>& image) const = 0;
     };
 
+    // Regular devices inherit to enable entering DFU state or implementing unsigned FW update.
     class updatable : public firmware_check_interface
     {
     public:
+        // Places the device in DFU (recovery) mode, where the DFU process can continue with update_device_interface.
+        // Restarts the device!
         virtual void enter_update_state() const = 0;
-        virtual std::vector<uint8_t> backup_flash( rs2_update_progress_callback_sptr callback) = 0;
-        virtual void update_flash(const std::vector<uint8_t>& image, rs2_update_progress_callback_sptr callback, int update_mode) = 0;
+
+        // Returns a backup of the current flash image. Optional: return an empty buffer if unsupported
+        virtual std::vector< uint8_t > backup_flash( rs2_update_progress_callback_sptr callback ) = 0;
+
+        // Unsigned FW update. When this is called, we're not in an "update state".
+        virtual void update_flash( const std::vector< uint8_t > & image,
+                                   rs2_update_progress_callback_sptr callback,
+                                   int update_mode )
+            = 0;
     };
 
     MAP_EXTENSION( RS2_EXTENSION_UPDATABLE, updatable );
 
+    // Recovery devices implement this to perform DFU with signed FW.
     class update_device_interface : public device_interface, public firmware_check_interface 
     {
     public:
-        virtual void update(const void* fw_image, int fw_image_size, rs2_update_progress_callback_sptr = nullptr) const = 0;
+        // Signed FW update
+        virtual void update( const void * fw_image, int fw_image_size, rs2_update_progress_callback_sptr = nullptr ) const = 0;
+
     protected:
         virtual const std::string& get_name() const = 0;
         virtual const std::string& get_product_line() const = 0;