Linux 2.6.35 下usb框架程序源码(6)

/*
     * release our reference to this urb, the USB core will eventually free
     * it entirely
     */
    usb_free_urb(urb);


    return writesize;

error_unanchor:
    usb_unanchor_urb(urb);
error:
    if (urb) {
        usb_free_coherent(dev->udev, writesize, buf, urb->transfer_dma);
        usb_free_urb(urb);
    }
    up(&dev->limit_sem);

exit:
    return retval;
}

static const struct file_operations skel_fops = {
    .owner =    THIS_MODULE,
    .read =        skel_read,
    .write =    skel_write,
    .open =        skel_open,
    .release =    skel_release,
    .flush =    skel_flush,
};

/*
 * usb class driver info in order to get a minor number from the usb core,
 * and to have the device registered with the driver core
 */
static struct usb_class_driver skel_class = {
    .name =        "skel%d",
    .fops =        &skel_fops,
    .minor_base =    USB_SKEL_MINOR_BASE,
};

static int skel_probe(struct usb_interface *interface,
              const struct usb_device_id *id)
{
    struct usb_skel *dev;
    struct usb_host_interface *iface_desc;
    struct usb_endpoint_descriptor *endpoint;
    size_t buffer_size;
    int i;
    int retval = -ENOMEM;

/* allocate memory for our device state and initialize it */
    dev = kzalloc(sizeof(*dev), GFP_KERNEL);
    if (!dev) {
        err("Out of memory");
        goto error;
    }
    kref_init(&dev->kref);
    sema_init(&dev->limit_sem, WRITES_IN_FLIGHT);
    mutex_init(&dev->io_mutex);
    spin_lock_init(&dev->err_lock);
    init_usb_anchor(&dev->submitted);
    init_completion(&dev->bulk_in_completion);

dev->udev = usb_get_dev(interface_to_usbdev(interface));
    dev->interface = interface;

/* set up the endpoint information */
    /* use only the first bulk-in and bulk-out endpoints */
    iface_desc = interface->cur_altsetting;
    for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
        endpoint = &iface_desc->endpoint[i].desc;

if (!dev->bulk_in_endpointAddr &&
            usb_endpoint_is_bulk_in(endpoint)) {
            /* we found a bulk in endpoint */
            buffer_size = le16_to_cpu(endpoint->wMaxPacketSize);
            dev->bulk_in_size = buffer_size;
            dev->bulk_in_endpointAddr = endpoint->bEndpointAddress;
            dev->bulk_in_buffer = kmalloc(buffer_size, GFP_KERNEL);
            if (!dev->bulk_in_buffer) {
                err("Could not allocate bulk_in_buffer");
                goto error;
            }
            dev->bulk_in_urb = usb_alloc_urb(0, GFP_KERNEL);
            if (!dev->bulk_in_urb) {
                err("Could not allocate bulk_in_urb");
                goto error;
            }
        }

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