USB skel_write_bulk_callback gives error -71

[Sendhilraj T]

Hello all,
I am trying to write imx21 board connected to my host. When I write 64 
bytes of data, the wrte call back gives error -71 which is protocol error.
Herewith I am giving the dmesg for my driver code along with the code.
I would like to where I am making mistake and how to rectify it?

Looking for ur help.
/T.S

dmesg
=====

skel_write
I have 64 bytes of data to write
buf 0 0x12
buf 1 0x13

::I am going to fill the bulk urb structure
I'm in usb.h::URB initialization SUCCESS
after URB submit
skel_release
skel_write_bulk_callback
STATUS::-71
=====dmesg over===

static void skel_write_bulk_callback(struct urb *urb, struct pt_regs 
*regs)
{

 
    struct usb_skel *dev;
    printk("%s\n ", __FUNCTION__);
    dev = (struct usb_skel *)urb->context;
    printk("STATUS::%d\n",urb->status);

    /* sync/async unlink faults aren't errors */
    if (urb->status &&
        !(urb->status == -ENOENT ||
          urb->status == -ECONNRESET ||
          urb->status == -ESHUTDOWN)) {
        dbg("%s - nonzero write bulk status received: %d",
            __FUNCTION__, urb->status);
    }

    /* free up our allocated buffer */
    usb_buffer_free(urb->dev, urb->transfer_buffer_length,
            urb->transfer_buffer, urb->transfer_dma);
    up(&dev->limit_sem);
}
static ssize_t skel_write(struct file *file, const char *user_buffer, 
size_t count, loff_t *ppos)
{
    struct usb_skel *dev;
    int retval = 0;
    struct urb *urb = NULL;
    char *buf = NULL;
    unsigned int pipe,temp,is_out;//PE added for testing
    struct usb_device *udev;//PE added for testing
    unsigned epnum ;//PE added for testing
    struct usb_host_endpoint *ep;//PE added for testing


    size_t writesize = min(count, (size_t)MAX_TRANSFER);
    printk("writesize::%d\n",writesize);
    printk("%s\n",__FUNCTION__);
    dev = (struct usb_skel *)file->private_data;


    /* verify that we actually have some data to write */
    if (count == 0)
    {
        printk("sw count 0\n");
        goto exit;
    }
    printk("I have %d bytes of data to write\n",count);

    /* limit the number of URBs in flight to stop a user from using up all 
RAM */
    if (down_interruptible(&dev->limit_sem)) {
        printk("sw down_interruptible\n");
        retval = -ERESTARTSYS;
        goto exit;
    }

    /* create a urb, and a buffer for it, and copy the data to the urb */
    urb = usb_alloc_urb(0, SLAB_NOIO);
    if (!urb) {
        printk("Skell Write usb alloc urb fail\n");
        retval = -ENOMEM;
        goto error;
    }

    buf = usb_buffer_alloc(dev->udev, writesize, SLAB_NOIO, 
&urb->transfer_dma);
    if (!buf) {
        retval = -ENOMEM;
        printk("sw usb buffer alloc fail\n");
        goto error;
    }

    if (copy_from_user(buf, user_buffer, writesize)) {
        retval = -EFAULT;
        printk("sw copy from user fail\n");
        goto error;
    }
    printk("buf 0 0x%x\n",buf[0]);//PE SEN added for testing
    printk("buf 1 0x%x\n",buf[1]);//PE SEN added for testing

    printk("::I am going to fill the bulk urb structure\n");
    /* initialize the urb properly */
    usb_fill_bulk_urb(urb, dev->udev,
              usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
              buf, writesize, skel_write_bulk_callback, dev);

    printk("URB initialization SUCCESS\n");
    urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
 

    /* send the data out the bulk port */
    retval = usb_submit_urb(urb, SLAB_ATOMIC);
    if (retval) {
        err("%s - failed submitting write urb, error %d", __FUNCTION__, 
retval);
        goto error;
    }

    printk("after URB submit\n");
    /* release our reference to this urb, the USB core will eventually 
free it entirely */
    usb_free_urb(urb);

#endif

exit:
    return writesize;

error:
    usb_buffer_free(dev->udev, writesize, buf, urb->transfer_dma);
    usb_free_urb(urb);
    up(&dev->limit_sem);
    return retval;

return writesize;
}