Android & libusb submit ISOC transfer error

Question

I write the Android application using libusb-1.0.9 and NDK (Android 4.0.4+) which has to read out audio-data from the USB-audiocard. The USB device from libusb opens successfully, and for it it is possible to receive all interfaces/EndPoint list. But when making ISOC transfer I faced with following unclear me error:

Debugging C code of making transfer:

static uint8_t buf[12];

static void cb_xfr(struct libusb_transfer *xfr)
{
     LOGD("USB callback\n");
     libusb_free_transfer(xfr);
}

JNIEXPORT jlong JNICALL
Java_com_usbtest_libusb_Libusb_makeISOCTransfer(JNIEnv *env, jobject this, jlong ms) 
{
      static struct libusb_transfer *xfr;
      int num_iso_pack = 1;
      unsigned char ep = 0x84;

       xfr = libusb_alloc_transfer(num_iso_pack);
       if (!xfr)  {
               LOGD("libusb_alloc_transfer: errno=%d\n", errno);
               return -1000;
       }

       LOGD("libusb_fill_iso_transfer: ep=%x, buf=%d, num iso=%d\n", ep, sizeof(buf), num_iso_pack);
       libusb_fill_iso_transfer(xfr, handle, ep, buf, sizeof(buf), num_iso_pack, cb_xfr, NULL, 0);
       libusb_set_iso_packet_lengths(xfr, sizeof(buf)/num_iso_pack);
       int res = libusb_submit_transfer(xfr);
       LOGD("libusb_submit_transfer: %d, errno=%d\n", res, errno);
       struct timeval tv;
       tv.tv_sec = 1;
       tv.tv_usec = 0;
       libusb_handle_events_timeout(NULL, &tv);
       return res;
}

After a call of libusb_submit_transfer I received a mistake: libusb_submit_transfer: -1, errno -2 And text messages:

 need 1 32k URBs for transfer
 first URB failed, easy peasy

EndPoint 0x84 is true for audio-in. The buf[] size = 12 - corresponds to the field wMaxPacketSize of this EndPoint. I request 1 transfer. Field of xfr->status = 0, but callback isn't caused. I thought that it is necessary to increase the buf buffer to 32K - I increased, but it didn't help. I tried to increase quantity of transfers. Same error. Prompt me please in what there can be a error?

Answer 1

I found the solution of this problem. In this topic http://en.it-usenet.org/thread/14995/14985/ there was a similar question, and the decision appeared to make detach for device HID USB interfaces.

I've used libusb_detach_kernel to detach the 2 hid drivers and submit transfer returned 0!!

I made libusb_detach_kernel_driver(handle, interface) for all interfaces of the device (0..3) after device opening, and as a result of libusb_submit_transfer return SUCCESS of transfer.