USB permission error using libusb

Question

I am trying to create a driver for a USB-to-DMX converter (Velleman VM116.)

The problem I have is that when I try to open the USB device and configure it it returns a error: Configurating USB failed: Operation not permitted, I cannot find what this error stands for. How can I configure the USB device the good way? This is my code:

int dmxOpen(){
    int result;

    struct usb_bus *busses;
    struct usb_bus *bus;

    usb_init();
    usb_find_busses();
    result = usb_find_devices();
    if(result < 0){
        perror("Finding USB devices failed");
        return 0;
    }

    usb_set_debug(1);

    busses = usb_get_busses();
    for(bus = busses; bus; bus = bus->next){
        for(dev = bus->devices; dev; dev = dev->next){
             if ((dev->descriptor.idVendor == 0x10cf) && (dev->descriptor.idProduct == 0x8062)){
                udev = usb_open(dev);
#if defined(LIBUSB_HAS_GET_DRIVER_NP) && defined(LIBUSB_HAS_DETACH_KERNEL_DRIVER_NP)
                usb_detach_kernel_driver_np(udev, 0);
#endif
                result = usb_set_configuration(udev, dev->descriptor.bNumConfigurations);
                if(result < 0){
                    usb_close(udev);
                    perror("Configurating USB failed");
                    return 0;
                }
                result = usb_claim_interface(udev, 0);
                if(result < 0){
                    usb_release_interface(udev, 1);
                    usb_close(udev);
                    perror("Claiming USB failed");
                    return 0;
                }
                return 1;
            }
        }
    }
    return 0;
}

By the way my computer is running on Linux Debian 64 bit, and this are the device specs:

Bus 010 Device 002: ID 10cf:8062 Velleman Components, Inc. 
Device Descriptor:
  bLength                18
  bDescriptorType         1
  bcdUSB               1.10
  bDeviceClass            0 (Defined at Interface level)
  bDeviceSubClass         0 
  bDeviceProtocol         0 
  bMaxPacketSize0         8
  idVendor           0x10cf Velleman Components, Inc.
  idProduct          0x8062 
  bcdDevice            0.00
  iManufacturer           1 
  iProduct                2 
  iSerial                 0 
  bNumConfigurations      1
  Configuration Descriptor:
    bLength                 9
    bDescriptorType         2
    wTotalLength           41
    bNumInterfaces          1
    bConfigurationValue     1
    iConfiguration          4 
    bmAttributes         0x80
      (Bus Powered)
    MaxPower              100mA
    Interface Descriptor:
      bLength                 9
      bDescriptorType         4
      bInterfaceNumber        0
      bAlternateSetting       0
      bNumEndpoints           2
      bInterfaceClass         3 Human Interface Device
      bInterfaceSubClass      0 No Subclass
      bInterfaceProtocol      0 None
      iInterface              0 
    HID Device Descriptor:
      bLength                 9
      bDescriptorType        33
      bcdHID               1.00
      bCountryCode            0 Not supported
      bNumDescriptors         1
      bDescriptorType        34 Report
      wDescriptorLength      29
     Report Descriptors: 
       ** UNAVAILABLE **
      Endpoint Descriptor:
    bLength                 7
    bDescriptorType         5
    bEndpointAddress     0x81  EP 1 IN
    bmAttributes            3
      Transfer Type            Interrupt
      Synch Type               None
      Usage Type               Data
    wMaxPacketSize     0x0008  1x 8 bytes
    bInterval              10
      Endpoint Descriptor:
    bLength                 7
    bDescriptorType         5
    bEndpointAddress     0x01  EP 1 OUT
    bmAttributes            3
      Transfer Type            Interrupt
      Synch Type               None
      Usage Type               Data
    wMaxPacketSize     0x0008  1x 8 bytes
    bInterval              10

Answer 1

It was indeed a privilege problem, when I sudo it it works

You can use a UDEV script to change the permissions of your USB device on attach. This way you don't need to be root to allow access via libusb.