The pfnCBKFUN is the callback function address, and the callback function must be written by yourself in your application. typedef void (*PCALLBACK_INQUIRY_DEVICE) (PBLUETOOTH_DEVICE_INFO pDevInfo) indicates that your callback function should be defined like:
void myCbkFunction(PBLUETOOTH_DEVICE_INFO pDevInfo). After you finish the function, register like this:
BT_RegisterCallback(EVENT_INQUIRY_DEVICE_REPORT, myCbkFunction)
After you register the callback function, you can just call this callback function with pDevInfo as input parameter.It's a pointer to BLUETOOTH_DEVICE_INFO or the address of a BLUETOOTH_DEVICE_INFO Variable:
BLUETOOTH_DEVICE_INFO devInfo = {0};
devInfo.dwSize = sizeof(BLUETOOTH_DEVICE_INFO);
((PCALLBACK_INQUIRY_DEVICE)pCbk)(&devInfo);