STM32G4 BSP's virtual com port fails to print character when UART register callback is turned on.

[rechiekho]

In a nutshell, as you turned on the UART register callback option as shown in the figure below, the virtual com port fails to print any items.

After further inspection, I believe it is a bug in `stm32g4xx_nucleo.c`, under function `BSP_COM_Init`. It seems like someone forget to index the `IsComMspCbValid` to find the validity of the given `COM`, as shown in code below. 

#if (USE_HAL_UART_REGISTER_CALLBACKS == 1)
static uint32_t IsComMspCbValid[COMn] = {0};
#endif

/**
  * @brief  Configures COM port.
  * @PAram  COM COM port to be configured.
  *         This parameter can be COM1
  * @PAram  COM_Init Pointer to a UART_HandleTypeDef structure that contains the
  *                  configuration information for the specified USART peripheral.
  * @retval BSP error code
  */
int32_t BSP_COM_Init(COM_TypeDef COM, COM_InitTypeDef *COM_Init)
{
  int32_t ret = BSP_ERROR_NONE;

  if(COM > COMn)
  {
    ret = BSP_ERROR_WRONG_PARAM;
  }
  else
  {
#if (USE_HAL_UART_REGISTER_CALLBACKS == 0)
    /* Init the UART Msp */
    COM1_MspInit(&hcom_uart[COM]);
#else
    if(IsComMspCbValid == 0U) // HERE
    {
      if(BSP_COM_RegisterDefaultMspCallbacks(COM) != BSP_ERROR_NONE)
      {
        return BSP_ERROR_MSP_FAILURE;
      }
    }
#endif

    if(MX_LPUART1_Init(&hcom_uart[COM], COM_Init) != HAL_OK)
    {
      return BSP_ERROR_PERIPH_FAILURE;
    }
  }

  return ret;
}

 This causes, `BSP_COM_RegisterDefaultMspCallbacks(COM)` never get called and the `COM` is never initialised. Thus the lack of response when using the `printf` function.

After adding indexing as shown in code below, the `printf` successfully work as intended.

    if (IsComMspCbValid[COM] == 0U)
    {
      if (BSP_COM_RegisterDefaultMspCallbacks(COM) != BSP_ERROR_NONE)
      {
        return BSP_ERROR_MSP_FAILURE;
      }
    }

Hopefully, the team could fix this small issue.