diff --git a/ports/stm32/usbdev/class/inc/usbd_cdc_msc_hid.h b/ports/stm32/usbdev/class/inc/usbd_cdc_msc_hid.h
index a6c92b114d..2283cbe856 100644
--- a/ports/stm32/usbdev/class/inc/usbd_cdc_msc_hid.h
+++ b/ports/stm32/usbdev/class/inc/usbd_cdc_msc_hid.h
@@ -72,6 +72,9 @@ typedef struct {
   
   uint32_t                 scsi_blk_addr_in_blks;
   uint32_t                 scsi_blk_len;
+
+  // operations of the underlying block device
+  USBD_StorageTypeDef *bdev_ops;
 } USBD_MSC_BOT_HandleTypeDef;
 
 typedef enum {
@@ -98,8 +101,6 @@ typedef struct _usbd_cdc_msc_hid_state_t {
     uint8_t *hid_desc;
     const uint8_t *hid_report_desc;
 
-    USBD_StorageTypeDef *MSC_fops;
-
     USBD_CDC_HandleTypeDef CDC_ClassData;
     USBD_MSC_BOT_HandleTypeDef MSC_BOT_ClassData;
     USBD_HID_HandleTypeDef HID_ClassData;
@@ -108,7 +109,6 @@ typedef struct _usbd_cdc_msc_hid_state_t {
     __ALIGN_BEGIN uint8_t usbd_config_desc[MAX_TEMPLATE_CONFIG_DESC_SIZE] __ALIGN_END;
 
     void *cdc;
-    void *msc;
     void *hid;
 } usbd_cdc_msc_hid_state_t;
 
@@ -132,7 +132,9 @@ uint8_t USBD_GetMode(usbd_cdc_msc_hid_state_t *usbd);
 uint8_t USBD_CDC_ReceivePacket(usbd_cdc_msc_hid_state_t *usbd, uint8_t *buf);
 uint8_t USBD_CDC_TransmitPacket(usbd_cdc_msc_hid_state_t *usbd, size_t len, const uint8_t *buf);
 
-uint8_t USBD_MSC_RegisterStorage(usbd_cdc_msc_hid_state_t *usbd, USBD_StorageTypeDef *fops);
+static inline void USBD_MSC_RegisterStorage(usbd_cdc_msc_hid_state_t *usbd, USBD_StorageTypeDef *fops) {
+    usbd->MSC_BOT_ClassData.bdev_ops = fops;
+}
 
 uint8_t USBD_HID_ReceivePacket(usbd_cdc_msc_hid_state_t *usbd, uint8_t *buf);
 int USBD_HID_CanSendReport(usbd_cdc_msc_hid_state_t *usbd);
diff --git a/ports/stm32/usbdev/class/src/usbd_cdc_msc_hid.c b/ports/stm32/usbdev/class/src/usbd_cdc_msc_hid.c
index 59eac15e26..379a8f32ce 100644
--- a/ports/stm32/usbdev/class/src/usbd_cdc_msc_hid.c
+++ b/ports/stm32/usbdev/class/src/usbd_cdc_msc_hid.c
@@ -662,9 +662,6 @@ static uint8_t USBD_CDC_MSC_HID_Init(USBD_HandleTypeDef *pdev, uint8_t cfgidx) {
                        USBD_EP_TYPE_BULK,
                        MSC_MAX_PACKET);
 
-        // Set the MSC data for SCSI and BOT to reference it
-        usbd->msc = &usbd->MSC_BOT_ClassData;
-
         // Init the BOT layer
         MSC_BOT_Init(pdev);
     }
@@ -715,7 +712,7 @@ static uint8_t USBD_CDC_MSC_HID_DeInit(USBD_HandleTypeDef *pdev, uint8_t cfgidx)
         USBD_LL_CloseEP(pdev, CDC_CMD_EP);
     }
 
-    if ((usbd->usbd_mode & USBD_MODE_MSC) && usbd->msc) {
+    if (usbd->usbd_mode & USBD_MODE_MSC) {
         // MSC component
 
         // close endpoints
@@ -724,9 +721,6 @@ static uint8_t USBD_CDC_MSC_HID_DeInit(USBD_HandleTypeDef *pdev, uint8_t cfgidx)
 
         // DeInit the BOT layer
         MSC_BOT_DeInit(pdev);
-
-        // clear the state pointer
-        usbd->msc = NULL;
     }
 
     if (usbd->usbd_mode & USBD_MODE_HID) {
@@ -788,7 +782,7 @@ static uint8_t USBD_CDC_MSC_HID_Setup(USBD_HandleTypeDef *pdev, USBD_SetupReqTyp
                 switch (req->bRequest) {
                     case BOT_GET_MAX_LUN:
                         if ((req->wValue  == 0) && (req->wLength == 1) && ((req->bmRequest & 0x80) == 0x80)) {
-                            usbd->MSC_BOT_ClassData.max_lun = usbd->MSC_fops->GetMaxLun();
+                            usbd->MSC_BOT_ClassData.max_lun = usbd->MSC_BOT_ClassData.bdev_ops->GetMaxLun();
                             USBD_CtlSendData(pdev, (uint8_t *)&usbd->MSC_BOT_ClassData.max_lun, 1);
                         } else {
                             USBD_CtlError(pdev, req);
@@ -992,16 +986,6 @@ uint8_t USBD_CDC_ReceivePacket(usbd_cdc_msc_hid_state_t *usbd, uint8_t *buf) {
     return USBD_OK;
 }
 
-uint8_t USBD_MSC_RegisterStorage(usbd_cdc_msc_hid_state_t *usbd, USBD_StorageTypeDef *fops) {
-    if (fops == NULL) {
-        return USBD_FAIL;
-    } else {
-        usbd->MSC_fops = fops;
-        usbd->pdev->pUserData = fops; // MSC uses pUserData because SCSI and BOT reference it
-        return USBD_OK;
-    }
-}
-
 // prepare OUT endpoint for reception
 uint8_t USBD_HID_ReceivePacket(usbd_cdc_msc_hid_state_t *usbd, uint8_t *buf) {
     // Suspend or Resume USB Out process
diff --git a/ports/stm32/usbdev/class/src/usbd_msc_bot.c b/ports/stm32/usbdev/class/src/usbd_msc_bot.c
index 7c6ceeecff..2fccd9e082 100644
--- a/ports/stm32/usbdev/class/src/usbd_msc_bot.c
+++ b/ports/stm32/usbdev/class/src/usbd_msc_bot.c
@@ -104,7 +104,7 @@ static void MSC_BOT_Abort(USBD_HandleTypeDef  *pdev);
 */
 void MSC_BOT_Init (USBD_HandleTypeDef  *pdev)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
     
   hmsc->bot_state  = USBD_BOT_IDLE;
   hmsc->bot_status = USBD_BOT_STATUS_NORMAL;
@@ -112,7 +112,7 @@ void MSC_BOT_Init (USBD_HandleTypeDef  *pdev)
   hmsc->scsi_sense_tail = 0;
   hmsc->scsi_sense_head = 0;
   
-  ((USBD_StorageTypeDef *)pdev->pUserData)->Init(0);
+  hmsc->bdev_ops->Init(0);
   
   USBD_LL_FlushEP(pdev, MSC_OUT_EP);
   USBD_LL_FlushEP(pdev, MSC_IN_EP);
@@ -132,7 +132,7 @@ void MSC_BOT_Init (USBD_HandleTypeDef  *pdev)
 */
 void MSC_BOT_Reset (USBD_HandleTypeDef  *pdev)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
     
   hmsc->bot_state  = USBD_BOT_IDLE;
   hmsc->bot_status = USBD_BOT_STATUS_RECOVERY;  
@@ -152,7 +152,7 @@ void MSC_BOT_Reset (USBD_HandleTypeDef  *pdev)
 */
 void MSC_BOT_DeInit (USBD_HandleTypeDef  *pdev)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   hmsc->bot_state  = USBD_BOT_IDLE;
 }
 
@@ -166,7 +166,7 @@ void MSC_BOT_DeInit (USBD_HandleTypeDef  *pdev)
 void MSC_BOT_DataIn (USBD_HandleTypeDef  *pdev, 
                      uint8_t epnum)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   switch (hmsc->bot_state)
   {
@@ -199,7 +199,7 @@ void MSC_BOT_DataIn (USBD_HandleTypeDef  *pdev,
 void MSC_BOT_DataOut (USBD_HandleTypeDef  *pdev, 
                       uint8_t epnum)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   switch (hmsc->bot_state)
   {
@@ -231,7 +231,7 @@ void MSC_BOT_DataOut (USBD_HandleTypeDef  *pdev,
 */
 static void  MSC_BOT_CBW_Decode (USBD_HandleTypeDef  *pdev)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   hmsc->csw.dTag = hmsc->cbw.dTag;
   hmsc->csw.dDataResidue = hmsc->cbw.dDataLength;
@@ -300,7 +300,7 @@ static void  MSC_BOT_SendData(USBD_HandleTypeDef  *pdev,
                               uint8_t* buf, 
                               uint16_t len)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   len = MIN (hmsc->cbw.dDataLength, len);
   hmsc->csw.dDataResidue -= len;
@@ -320,7 +320,7 @@ static void  MSC_BOT_SendData(USBD_HandleTypeDef  *pdev,
 void  MSC_BOT_SendCSW (USBD_HandleTypeDef  *pdev,
                               uint8_t CSW_Status)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   hmsc->csw.dSignature = USBD_BOT_CSW_SIGNATURE;
   hmsc->csw.bStatus = CSW_Status;
@@ -348,7 +348,7 @@ void  MSC_BOT_SendCSW (USBD_HandleTypeDef  *pdev,
 
 static void  MSC_BOT_Abort (USBD_HandleTypeDef  *pdev)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   if ((hmsc->cbw.bmFlags == 0) && 
       (hmsc->cbw.dDataLength != 0) &&
@@ -377,7 +377,7 @@ static void  MSC_BOT_Abort (USBD_HandleTypeDef  *pdev)
 
 void  MSC_BOT_CplClrFeature (USBD_HandleTypeDef  *pdev, uint8_t epnum)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   if(hmsc->bot_status == USBD_BOT_STATUS_ERROR )/* Bad CBW Signature */
   {
diff --git a/ports/stm32/usbdev/class/src/usbd_msc_scsi.c b/ports/stm32/usbdev/class/src/usbd_msc_scsi.c
index 0664883adb..50cd5b9715 100644
--- a/ports/stm32/usbdev/class/src/usbd_msc_scsi.c
+++ b/ports/stm32/usbdev/class/src/usbd_msc_scsi.c
@@ -190,7 +190,7 @@ int8_t SCSI_ProcessCmd(USBD_HandleTypeDef  *pdev,
 */
 static int8_t SCSI_TestUnitReady(USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t *params)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
     
   /* case 9 : Hi > D0 */
   if (hmsc->cbw.dDataLength != 0)
@@ -202,7 +202,7 @@ static int8_t SCSI_TestUnitReady(USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t
     return -1;
   }  
   
-  if(((USBD_StorageTypeDef *)pdev->pUserData)->IsReady(lun) !=0 )
+  if(hmsc->bdev_ops->IsReady(lun) !=0 )
   {
     SCSI_SenseCode(pdev,
                    lun,
@@ -227,7 +227,7 @@ static int8_t  SCSI_Inquiry(USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t *par
 {
   uint8_t* pPage;
   uint16_t len;
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   if (params[1] & 0x01)/*Evpd is set*/
   {
@@ -237,7 +237,7 @@ static int8_t  SCSI_Inquiry(USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t *par
   else
   {
     
-    pPage = (uint8_t *)&((USBD_StorageTypeDef *)pdev->pUserData)->pInquiry[lun * STANDARD_INQUIRY_DATA_LEN];
+    pPage = (uint8_t *)&hmsc->bdev_ops->pInquiry[lun * STANDARD_INQUIRY_DATA_LEN];
     len = pPage[4] + 5;
     
     if (params[4] <= len)
@@ -264,9 +264,9 @@ static int8_t  SCSI_Inquiry(USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t *par
 */
 static int8_t SCSI_ReadCapacity10(USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t *params)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
-  if(((USBD_StorageTypeDef *)pdev->pUserData)->GetCapacity(lun, &hmsc->scsi_blk_nbr, &hmsc->scsi_blk_size) != 0)
+  if(hmsc->bdev_ops->GetCapacity(lun, &hmsc->scsi_blk_nbr, &hmsc->scsi_blk_size) != 0)
   {
     SCSI_SenseCode(pdev,
                    lun,
@@ -300,7 +300,7 @@ static int8_t SCSI_ReadCapacity10(USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_
 */
 static int8_t SCSI_ReadFormatCapacity(USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t *params)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   uint16_t blk_size;
   uint32_t blk_nbr;
@@ -311,7 +311,7 @@ static int8_t SCSI_ReadFormatCapacity(USBD_HandleTypeDef  *pdev, uint8_t lun, ui
     hmsc->bot_data[i] = 0;
   }
   
-  if(((USBD_StorageTypeDef *)pdev->pUserData)->GetCapacity(lun, &blk_nbr, &blk_size) != 0)
+  if(hmsc->bdev_ops->GetCapacity(lun, &blk_nbr, &blk_size) != 0)
   {
     SCSI_SenseCode(pdev,
                    lun,
@@ -345,7 +345,7 @@ static int8_t SCSI_ReadFormatCapacity(USBD_HandleTypeDef  *pdev, uint8_t lun, ui
 */
 static int8_t SCSI_ModeSense6 (USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t *params)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   uint16_t len = 8 ;
   hmsc->bot_data_length = len;
   
@@ -367,7 +367,7 @@ static int8_t SCSI_ModeSense6 (USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t *
 static int8_t SCSI_ModeSense10 (USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t *params)
 {
   uint16_t len = 8;
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   hmsc->bot_data_length = len;
 
@@ -381,7 +381,7 @@ static int8_t SCSI_ModeSense10 (USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t
 
 static int8_t SCSI_SynchronizeCache(USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t *params) {
     // nothing to synchronize, so just return "success"
-    USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
     hmsc->bot_data_length = 0;
     return 0;
 }
@@ -397,7 +397,7 @@ static int8_t SCSI_SynchronizeCache(USBD_HandleTypeDef  *pdev, uint8_t lun, uint
 static int8_t SCSI_RequestSense (USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t *params)
 {
   uint8_t i;
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   for(i=0 ; i < REQUEST_SENSE_DATA_LEN ; i++) 
   {
@@ -439,7 +439,7 @@ static int8_t SCSI_RequestSense (USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t
 */
 void SCSI_SenseCode(USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t sKey, uint8_t ASC)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   hmsc->scsi_sense[hmsc->scsi_sense_tail].Skey  = sKey;
   hmsc->scsi_sense[hmsc->scsi_sense_tail].w.ASC = ASC << 8;
@@ -458,14 +458,14 @@ void SCSI_SenseCode(USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t sKey, uint8_
 */
 static int8_t SCSI_StartStopUnit(USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t *params)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   hmsc->bot_data_length = 0;
 
   // On Mac OS X, when the device is ejected a SCSI_START_STOP_UNIT command is sent.
   // Bit 0 of params[4] is the START bit.
   // If we get a stop, we must really stop the device so that the Mac does not
   // automatically remount it.
-  ((USBD_StorageTypeDef *)pdev->pUserData)->StartStopUnit(lun, params[4] & 1);
+  hmsc->bdev_ops->StartStopUnit(lun, params[4] & 1);
 
   return 0;
 }
@@ -479,9 +479,9 @@ static int8_t SCSI_StartStopUnit(USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t
 */
 static int8_t SCSI_AllowMediumRemoval(USBD_HandleTypeDef  *pdev, uint8_t lun, uint8_t *params)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   hmsc->bot_data_length = 0;
-  ((USBD_StorageTypeDef *)pdev->pUserData)->PreventAllowMediumRemoval(lun, params[0]);
+  hmsc->bdev_ops->PreventAllowMediumRemoval(lun, params[0]);
   return 0;
 }
 
@@ -494,7 +494,7 @@ static int8_t SCSI_AllowMediumRemoval(USBD_HandleTypeDef  *pdev, uint8_t lun, ui
 */
 static int8_t SCSI_Read10(USBD_HandleTypeDef  *pdev, uint8_t lun , uint8_t *params)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   if(hmsc->bot_state == USBD_BOT_IDLE)  /* Idle */
   {
@@ -510,7 +510,7 @@ static int8_t SCSI_Read10(USBD_HandleTypeDef  *pdev, uint8_t lun , uint8_t *para
       return -1;
     }    
     
-    if(((USBD_StorageTypeDef *)pdev->pUserData)->IsReady(lun) !=0 )
+    if(hmsc->bdev_ops->IsReady(lun) !=0 )
     {
       SCSI_SenseCode(pdev,
                      lun,
@@ -562,7 +562,7 @@ static int8_t SCSI_Read10(USBD_HandleTypeDef  *pdev, uint8_t lun , uint8_t *para
 
 static int8_t SCSI_Write10 (USBD_HandleTypeDef  *pdev, uint8_t lun , uint8_t *params)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   if (hmsc->bot_state == USBD_BOT_IDLE) /* Idle */
   {
@@ -579,7 +579,7 @@ static int8_t SCSI_Write10 (USBD_HandleTypeDef  *pdev, uint8_t lun , uint8_t *pa
     }
     
     /* Check whether Media is ready */
-    if(((USBD_StorageTypeDef *)pdev->pUserData)->IsReady(lun) !=0 )
+    if(hmsc->bdev_ops->IsReady(lun) !=0 )
     {
       SCSI_SenseCode(pdev,
                      lun,
@@ -589,7 +589,7 @@ static int8_t SCSI_Write10 (USBD_HandleTypeDef  *pdev, uint8_t lun , uint8_t *pa
     } 
     
     /* Check If media is write-protected */
-    if(((USBD_StorageTypeDef *)pdev->pUserData)->IsWriteProtected(lun) !=0 )
+    if(hmsc->bdev_ops->IsWriteProtected(lun) !=0 )
     {
       SCSI_SenseCode(pdev,
                      lun,
@@ -652,7 +652,7 @@ static int8_t SCSI_Write10 (USBD_HandleTypeDef  *pdev, uint8_t lun , uint8_t *pa
 
 static int8_t SCSI_Verify10(USBD_HandleTypeDef  *pdev, uint8_t lun , uint8_t *params)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   if ((params[1]& 0x02) == 0x02) 
   {
@@ -687,7 +687,7 @@ static int8_t SCSI_Verify10(USBD_HandleTypeDef  *pdev, uint8_t lun , uint8_t *pa
 */
 static int8_t SCSI_CheckAddressRange (USBD_HandleTypeDef  *pdev, uint8_t lun , uint32_t blk_offset , uint16_t blk_nbr)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   if ((blk_offset + blk_nbr) > hmsc->scsi_blk_nbr )
   {
@@ -708,12 +708,12 @@ static int8_t SCSI_CheckAddressRange (USBD_HandleTypeDef  *pdev, uint8_t lun , u
 */
 static int8_t SCSI_ProcessRead (USBD_HandleTypeDef  *pdev, uint8_t lun)
 {
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   uint32_t len;
   
   len = MIN(hmsc->scsi_blk_len , MSC_MEDIA_PACKET); 
   
-  if( ((USBD_StorageTypeDef *)pdev->pUserData)->Read(lun ,
+  if( hmsc->bdev_ops->Read(lun ,
                               hmsc->bot_data, 
                               hmsc->scsi_blk_addr_in_blks,
                               len / hmsc->scsi_blk_size) < 0)
@@ -756,11 +756,11 @@ static int8_t SCSI_ProcessRead (USBD_HandleTypeDef  *pdev, uint8_t lun)
 static int8_t SCSI_ProcessWrite (USBD_HandleTypeDef  *pdev, uint8_t lun)
 {
   uint32_t len;
-  USBD_MSC_BOT_HandleTypeDef  *hmsc = ((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->msc;
+  USBD_MSC_BOT_HandleTypeDef *hmsc = &((usbd_cdc_msc_hid_state_t*)pdev->pClassData)->MSC_BOT_ClassData;
   
   len = MIN(hmsc->scsi_blk_len , MSC_MEDIA_PACKET); 
   
-  if(((USBD_StorageTypeDef *)pdev->pUserData)->Write(lun ,
+  if(hmsc->bdev_ops->Write(lun ,
                               hmsc->bot_data, 
                               hmsc->scsi_blk_addr_in_blks,
                               len / hmsc->scsi_blk_size) < 0)