Double buffering fix for reception. In the case of double buffering,

it is impossible to determine exactly how large the allocated buffer should be.
To achieve double-buffering acceleration, the PCD_FreeUserBuffer call must
occur before the HAL_PCD_DataOutStageCallback call. But the real data buffer
can be allocated only in this callback. It turns out that the approach itself
needs to be changed - always allocate maximum allowable endpoint buffer size
(it's already happends in USB_ActivateEndpoint). At the same time we need to
check the size of the data received. This check be done at the time of data
receipt. During reception confirmation, it may be that there is no allocated
buffer at all. In this case, we will have to leave the filled PMA intact and
not complete its release. In this case, this operation will be repeated in
HAL_PCD_EP_ReceiveData.

system/Drivers/STM32F1xx_HAL_Driver/Inc/stm32f1xx_ll_usb.h

@@ -160,6 +160,9 @@ typedef struct
   uint32_t  xfer_len;       /*!< Current transfer length                                                  */
 
   uint32_t  xfer_count;     /*!< Partial transfer length in case of multi packet transfer                 */
+
+  uint16_t  pending0;        /*!, Fact, that double buffering transfer have pended data                    */
+  uint16_t  pending1;        /*!, Fact, that double buffering transfer have pended data                    */
 }USB_OTG_EPTypeDef;
 
 typedef struct
@@ -269,20 +272,24 @@ typedef struct
 
   uint8_t   doublebuffer;    /*!< Double buffer enable
                                  This parameter can be 0 or 1                                             */
-  
-  uint16_t  tx_fifo_num;    /*!< This parameter is not required by USB Device FS peripheral, it is used 
+
+  uint16_t  tx_fifo_num;    /*!< This parameter is not required by USB Device FS peripheral, it is used
                                  only by USB OTG FS peripheral    
                                  This parameter is added to ensure compatibility across USB peripherals   */
 
   uint32_t  maxpacket;      /*!< Endpoint Max packet size
                                  This parameter must be a number between Min_Data = 0 and Max_Data = 64KB */
 
   uint8_t   *xfer_buff;     /*!< Pointer to transfer buffer                                               */
-
+
+
   uint32_t  xfer_len;       /*!< Current transfer length                                                  */
 
   uint32_t  xfer_count;     /*!< Partial transfer length in case of multi packet transfer                 */
 
+  uint16_t  pending0;        /*!, Fact, that double buffering transfer have pended data                    */
+  uint16_t  pending1;        /*!, Fact, that double buffering transfer have pended data                    */
+
 } USB_EPTypeDef;
 #endif /* USB */
 /**