stm32 USB Device模块学习，求大神指点~~~

liuchang

大神：小弟最近在学习stm32 USB Device模块，很多不懂，希望大神不惜赐教~~~
uint8_t Setup0_Process(void)
{
  union
  {
    uint8_t* b;
    uint16_t* w;
  } pBuf;

#ifdef STM32F10X_CL
  USB_OTG_EP *ep;
  uint16_t offset = 0;

  ep = PCD_GetOutEP(ENDP0);
  pBuf.b = ep->xfer_buff;
#else  
  uint16_t offset = 1;

  pBuf.b = PMAAddr + (uint8_t *)(_GetEPRxAddr(ENDP0) * 2);
#endif /* STM32F10X_CL */

  if (pInformation->ControlState != PAUSE)/*请问大神：该如何理解ControlState？？？（ControlState属于DEVICE_INFO 结构体，如下）*/
  {
    pInformation->USBbmRequestType = *pBuf.b++; /* bmRequestType */
    pInformation->USBbRequest = *pBuf.b++; /* bRequest */
    pBuf.w += offset;  /* word not accessed because of 32 bits addressing */
    pInformation->USBwValue = ByteSwap(*pBuf.w++); /* wValue */
    pBuf.w += offset;  /* word not accessed because of 32 bits addressing */
    pInformation->USBwIndex  = ByteSwap(*pBuf.w++); /* wIndex */
    pBuf.w += offset;  /* word not accessed because of 32 bits addressing */
    pInformation->USBwLength = *pBuf.w; /* wLength */
  }

  pInformation->ControlState = SETTING_UP;
  if (pInformation->USBwLength == 0)
  {
    /* Setup with no data stage */
    NoData_Setup0();
  }
  else
  {
    /* Setup with data stage */
    Data_Setup0();
  }
  return Post0_Process();
}
/*******************************************************************/
typedef struct _DEVICE_INFO
{
  uint8_t USBbmRequestType;       /* bmRequestType */
  uint8_t USBbRequest;            /* bRequest */
  uint16_t_uint8_t USBwValues;         /* wValue */
  uint16_t_uint8_t USBwIndexs;         /* wIndex */
  uint16_t_uint8_t USBwLengths;        /* wLength */

  uint8_t ControlState;           /* of type CONTROL_STATE */
  uint8_t Current_Feature;
  uint8_t Current_Configuration;   /* Selected configuration */
  uint8_t Current_Interface;       /* Selected interface of current configuration */
  uint8_t Current_AlternateSetting;/* Selected Alternate Setting of current
                                     interface*/

  ENDPOINT_INFO Ctrl_Info;
}DEVICE_INFO;/*这个结构体的意义是什么？恳请大神指教*/

flyleaf

DEVICE_INFO是usb协议规定需求的usb设备信息，与usb主机通讯时需要把这些信息交给主机，以便让主机识别