usb设备,如何获取设备描述符?
这是我写的获取设备描述符的程序,但是获取的设备描述符不正确。
请大家帮我看看哪儿错了?
#define Ezusb_IOCTL_INDEX 0x0000
#define IOCTL_Ezusb_GET_DEVICE_DESCRIPTOR CTL_CODE(FILE_DEVICE_UNKNOWN, \
Ezusb_IOCTL_INDEX+4, \
METHOD_BUFFERED, \
FILE_ANY_ACCESS)
HANDLE hDevice = NULL;
bool bResult= FALSE;
ULONG nBytes;
USB_DEVICE_DESCRIPTOR output;
bResult=DeviceIoControl(hDevice,
IOCTL_Ezusb_GET_DEVICE_DESCRIPTOR,
NULL,
0,
&output,
sizeof(USB_DEVICE_DESCRIPTOR),
&nBytes,
NULL); 这个NULL这里有个警告warning C4800: 'int' : forcing value to bool 'true' or 'false' (performance warning)
这是怎么回事?