SetupDiGetDeviceInterfaceDetail returns only "\" for the path of all USB-HID objects

Question

I can tell how many USB HID devices I have (7), but every time I try to get the details on any device, the path returned for it is always "\", so I can’t access the device at all. I use code that is very similar in procedure to this code:

HANDLE connectDeviceNumber(DWORD deviceIndex)
{
    GUID hidGUID;
    HDEVINFO hardwareDeviceInfoSet;
    SP_DEVICE_INTERFACE_DATA deviceInterfaceData;
    PSP_INTERFACE_DEVICE_DETAIL_DATA deviceDetail;
    ULONG requiredSize;
    HANDLE deviceHandle = INVALID_HANDLE_VALUE;
    DWORD result;

    //Get the HID GUID value - used as mask to get list of devices
    HidD_GetHidGuid (&hidGUID);

    //Get a list of devices matching the criteria (hid interface, present)
    hardwareDeviceInfoSet = SetupDiGetClassDevs (&hidGUID,
                                                 NULL, // Define no enumerator (global)
                                                 NULL, // Define no
                                                 (DIGCF_PRESENT | // Only Devices present
                                                 DIGCF_DEVICEINTERFACE)); // Function class devices.

    deviceInterfaceData.cbSize = sizeof(SP_DEVICE_INTERFACE_DATA);

    //Go through the list and get the interface data
    result = SetupDiEnumDeviceInterfaces (hardwareDeviceInfoSet,
                                          NULL, //infoData,
                                          &hidGUID, //interfaceClassGuid,
                                          deviceIndex, 
                                          &deviceInterfaceData);

    /* Failed to get a device - possibly the index is larger than the number of devices */
    if (result == FALSE)
    {
        SetupDiDestroyDeviceInfoList (hardwareDeviceInfoSet);
        Log("hidin: -- failed to get specified device number");
        return INVALID_HANDLE_VALUE;
    }

    //Get the details with null values to get the required size of the buffer
    SetupDiGetDeviceInterfaceDetail (hardwareDeviceInfoSet,
                                     &deviceInterfaceData,
                                     NULL, //interfaceDetail,
                                     0, //interfaceDetailSize,
                                     &requiredSize,
                                     0); //infoData))

    //Allocate the buffer
    deviceDetail = (PSP_INTERFACE_DEVICE_DETAIL_DATA)malloc(requiredSize);
    deviceDetail->cbSize = sizeof(SP_INTERFACE_DEVICE_DETAIL_DATA);

    //Fill the buffer with the device details
    if (!SetupDiGetDeviceInterfaceDetail (hardwareDeviceInfoSet,
                                          &deviceInterfaceData,
                                          deviceDetail,
                                          requiredSize,
                                          &requiredSize,
                                          NULL)) 
    {
        SetupDiDestroyDeviceInfoList (hardwareDeviceInfoSet);
        free (deviceDetail);
        Log("hidin: -- failed to get device info");
        return INVALID_HANDLE_VALUE;
    }

    Log("Opening device with path: %s", deviceDetail->DevicePath);

Answer 1

Perhaps you are compiling with UNICODE? Then the log line of Log () is incorrect. Fix:

   Log("Opening device with path: %ls", deviceDetail->DevicePath);

Answer 2

The documentation for SetupDiEnumDeviceInterfacesstates that you must first call it using deviceIndex == 0; You must not skip values.