自娛自樂6之Linux gadget驅動5（自編gadget驅動，包涵與之通訊的主機usb驅動，已調試通過）

這個代碼調試，你首先要保證你的udc驅動沒用問題，這個有些矛盾，應爲我本來要用gadget驅動來調試udc驅動，結果反過來了。

這是在zero基礎改的，大概的改動

1. 去掉loop。

2. sink的讀寫去掉了。

3. 增加了一個misc，通過fs去讀寫數據。

4. setup的特殊請求去掉了。

之前的文章已經把大部分的東西說完了，所以代碼沒有太多的註釋。請結合之前的文章閱讀。

我用了一個完成量，在沒有數據時，讀可能會死在那。這個可以優化一下，我就不做了。

還有就是主機是虛擬機的usb，linux-2.6.18（無恥的告訴你就是usb-skeleton驅動），gadget是板子的，linux-3.2.36

gadget_transfer.c //linux-3.2.36

/* #define VERBOSE_DEBUG */

#include <linux/kernel.h>
#include <linux/slab.h>
#include <linux/utsname.h>
#include <linux/device.h>
#include <linux/module.h>
#include <linux/miscdevice.h>
#include <linux/completion.h>
#include <linux/fs.h>

#include <asm/uaccess.h>

#define CONFIG_USB_GADGET_VBUS_DRAW 500

#include "composite.c"
#include "usbstring.c"
#include "config.c"
#include "epautoconf.c"

#define BUFLEN 4096

struct f_sourcesink {
    struct usb_function    function;

    struct usb_ep        *in_ep;
    struct usb_ep        *out_ep;

    struct completion gdt_completion;
    char data[BUFLEN];
    unsigned actual;//數據實際長度
};

static inline struct f_sourcesink *func_to_ss(struct usb_function *f)
{
    return container_of(f, struct f_sourcesink, function);
}

/*-------------------------------------------------------------------------*/
//接口描述符
static struct usb_interface_descriptor source_sink_intf = {
    .bLength =        sizeof source_sink_intf,
    .bDescriptorType =    USB_DT_INTERFACE,

    .bNumEndpoints =    2,
    .bInterfaceClass =    USB_CLASS_VENDOR_SPEC,
    /* .iInterface = DYNAMIC */
};

/* full speed support: */
//全速設備端點描述符
static struct usb_endpoint_descriptor fs_source_desc = {
    .bLength =        USB_DT_ENDPOINT_SIZE,
    .bDescriptorType =    USB_DT_ENDPOINT,

    .bEndpointAddress =    USB_DIR_IN,
    .bmAttributes =        USB_ENDPOINT_XFER_BULK,
};

static struct usb_endpoint_descriptor fs_sink_desc = {
    .bLength =        USB_DT_ENDPOINT_SIZE,
    .bDescriptorType =    USB_DT_ENDPOINT,

    .bEndpointAddress =    USB_DIR_OUT,
    .bmAttributes =        USB_ENDPOINT_XFER_BULK,
};

static struct usb_descriptor_header *fs_source_sink_descs[] = {
    (struct usb_descriptor_header *) &source_sink_intf,
    (struct usb_descriptor_header *) &fs_sink_desc,
    (struct usb_descriptor_header *) &fs_source_desc,
    NULL,
};

/* high speed support: */
//高速設備端點描述符
static struct usb_endpoint_descriptor hs_source_desc = {
    .bLength =        USB_DT_ENDPOINT_SIZE,
    .bDescriptorType =    USB_DT_ENDPOINT,

    .bmAttributes =        USB_ENDPOINT_XFER_BULK,
    .wMaxPacketSize =    cpu_to_le16(512),
};

static struct usb_endpoint_descriptor hs_sink_desc = {
    .bLength =        USB_DT_ENDPOINT_SIZE,
    .bDescriptorType =    USB_DT_ENDPOINT,

    .bmAttributes =        USB_ENDPOINT_XFER_BULK,
    .wMaxPacketSize =    cpu_to_le16(512),
};

static struct usb_descriptor_header *hs_source_sink_descs[] = {
    (struct usb_descriptor_header *) &source_sink_intf,
    (struct usb_descriptor_header *) &hs_source_desc,
    (struct usb_descriptor_header *) &hs_sink_desc,
    NULL,
};


/* function-specific strings: */
static struct usb_string strings_sourcesink[] = {
    [0].s = "source and sink data",
    {  }            /* end of list */
};

static struct usb_gadget_strings stringtab_sourcesink = {
    .language    = 0x0409,    /* en-us */
    .strings    = strings_sourcesink,
};

static struct usb_gadget_strings *sourcesink_strings[] = {
    &stringtab_sourcesink,
    NULL,
};

/*-------------------------------------------------------------------------*/

static const char longname[] = "Gadget gadget_transfer";

#define DRIVER_VENDOR_NUM       0x0ff0          
#define DRIVER_PRODUCT_NUM      0x0ff0          

/*-------------------------------------------------------------------------*/

//usb設備描述符
static struct usb_device_descriptor device_desc = {
    .bLength =        sizeof device_desc,
    .bDescriptorType =    USB_DT_DEVICE,

    .bcdUSB =        cpu_to_le16(0x0200),
    .bDeviceClass =        USB_CLASS_VENDOR_SPEC,

    .idVendor =        cpu_to_le16(DRIVER_VENDOR_NUM),
    .idProduct =        cpu_to_le16(DRIVER_PRODUCT_NUM),
    .bNumConfigurations =    2,
};

/* string IDs are assigned dynamically */

#define STRING_MANUFACTURER_IDX        0
#define STRING_PRODUCT_IDX        1
#define STRING_SERIAL_IDX        2

static char manufacturer[50];

/* default serial number takes at least two packets */
static char serial[] = "0123456789.0123456789.0123456789";

static struct usb_string strings_dev[] = {
    [STRING_MANUFACTURER_IDX].s = manufacturer,
    [STRING_PRODUCT_IDX].s = longname,
    [STRING_SERIAL_IDX].s = serial,
    {  }            /* end of list */
};

static struct usb_gadget_strings stringtab_dev = {
    .language    = 0x0409,    /* en-us */
    .strings    = strings_dev,
};

static struct usb_gadget_strings *dev_strings[] = {
    &stringtab_dev,
    NULL,
};

/*-------------------------------------------------------------------------*/

struct usb_request *alloc_ep_req(struct usb_ep *ep)
{
    struct usb_request    *req;

    //看過之前udc的request，就知道這個就是個kzalloc
    req = usb_ep_alloc_request(ep, GFP_ATOMIC);
    if (req) {
        req->length = BUFLEN;
        req->buf = kmalloc(BUFLEN, GFP_ATOMIC);
        if (!req->buf) {
            usb_ep_free_request(ep, req);
            req = NULL;
        }
    }
    return req;
}

void free_ep_req(struct usb_ep *ep, struct usb_request *req)
{
    kfree(req->buf);
    usb_ep_free_request(ep, req);
}

static void disable_ep(struct usb_composite_dev *cdev, struct usb_ep *ep)
{
    int            value;

    if (ep->driver_data) {
        value = usb_ep_disable(ep);
        ep->driver_data = NULL;
    }
}

void disable_endpoints(struct usb_composite_dev *cdev,
        struct usb_ep *in, struct usb_ep *out)
{
    disable_ep(cdev, in);
    disable_ep(cdev, out);
}

/*-------------------------------------------------------------------------*/

static int __init
sourcesink_bind(struct usb_configuration *c, struct usb_function *f)
{
    struct usb_composite_dev *cdev = c->cdev;
    struct f_sourcesink    *ss = func_to_ss(f);
    int    id;


    id = usb_interface_id(c, f);
    if (id < 0)
        return id;
    source_sink_intf.bInterfaceNumber = id;

    ss->in_ep = usb_ep_autoconfig(cdev->gadget, &fs_source_desc);
    if (!ss->in_ep) {
autoconf_fail:
        return -ENODEV;
    }
    ss->in_ep->driver_data = cdev;    /* claim */

    ss->out_ep = usb_ep_autoconfig(cdev->gadget, &fs_sink_desc);
    if (!ss->out_ep)
        goto autoconf_fail;
    ss->out_ep->driver_data = cdev;    /* claim */

    /* support high speed hardware */
    if (gadget_is_dualspeed(c->cdev->gadget)) {
        hs_source_desc.bEndpointAddress =
                fs_source_desc.bEndpointAddress;
        hs_sink_desc.bEndpointAddress =
                fs_sink_desc.bEndpointAddress;
        f->hs_descriptors = hs_source_sink_descs;
    }

    return 0;
}

static void
sourcesink_unbind(struct usb_configuration *c, struct usb_function *f)
{
    kfree(func_to_ss(f));
}

static void disable_source_sink(struct f_sourcesink *ss)
{
    struct usb_composite_dev    *cdev;

    cdev = ss->function.config->cdev;
    disable_endpoints(cdev, ss->in_ep, ss->out_ep);//就是disable了in和out
}

static int
enable_source_sink(struct usb_composite_dev *cdev, struct f_sourcesink *ss)
{
    int                    result = 0;
    struct usb_ep                *ep;

    /* one endpoint writes (sources) zeroes IN (to the host) */
    ep = ss->in_ep;
    result = config_ep_by_speed(cdev->gadget, &(ss->function), ep);
    if (result)
        return result;
    result = usb_ep_enable(ep);
    if (result < 0)
        return result;
    ep->driver_data = ss;

    /* one endpoint reads (sinks) anything OUT (from the host) */
    ep = ss->out_ep;
    result = config_ep_by_speed(cdev->gadget, &(ss->function), ep);
    if (result)
        goto fail;
    result = usb_ep_enable(ep);
    if (result < 0)
        goto fail;
    ep->driver_data = ss;

    return result;

fail:
    ep = ss->in_ep;
    usb_ep_disable(ep);
    ep->driver_data = NULL;

    return result;
}

static int sourcesink_set_alt(struct usb_function *f,
        unsigned intf, unsigned alt)
{
    struct f_sourcesink    *ss = func_to_ss(f);
    struct usb_composite_dev *cdev = f->config->cdev;

    /* we know alt is zero */
    if (ss->in_ep->driver_data)
        disable_source_sink(ss);
    return enable_source_sink(cdev, ss);
}

static void sourcesink_disable(struct usb_function *f)
{
    struct f_sourcesink    *ss = func_to_ss(f);

    disable_source_sink(ss);
}

/*-------------------------------------------------------------------------*/

static struct f_sourcesink    *ss;

static int __init sourcesink_bind_config(struct usb_configuration *c)
{
    int            status;

    ss = kzalloc(sizeof *ss, GFP_KERNEL);
    if (!ss)
        return -ENOMEM;

    init_completion(&ss->gdt_completion);

    ss->function.name = "source/sink";
    ss->function.descriptors = fs_source_sink_descs;
    ss->function.bind = sourcesink_bind;
    ss->function.unbind = sourcesink_unbind;
    ss->function.set_alt = sourcesink_set_alt;
    ss->function.disable = sourcesink_disable;

    status = usb_add_function(c, &ss->function);
    if (status)
        kfree(ss);
    return status;
}

static int sourcesink_setup(struct usb_configuration *c,
        const struct usb_ctrlrequest *ctrl)
{
    return 0;
}

static struct usb_configuration sourcesink_driver = {
    .label        = "source/sink",
    .strings    = sourcesink_strings,
    .setup        = sourcesink_setup,
    .bConfigurationValue = 3,
    .bmAttributes    = USB_CONFIG_ATT_SELFPOWER,
    /* .iConfiguration = DYNAMIC */
};

/**
 * sourcesink_add - add a source/sink testing configuration to a device
 * @cdev: the device to support the configuration
 */
static int __init sourcesink_add(struct usb_composite_dev *cdev)
{
    int id;

    /* allocate string ID(s) */
    id = usb_string_id(cdev);
    if (id < 0)
        return id;
    strings_sourcesink[0].id = id;

    source_sink_intf.iInterface = id;
    sourcesink_driver.iConfiguration = id;

    return usb_add_config(cdev, &sourcesink_driver, sourcesink_bind_config);
}

struct gadget_misc
{
    struct miscdevice miscdevp;
};

static void source_sink_complete(struct usb_ep *ep, struct usb_request *req)
{
    int            status = req->status;

    switch (status) {

    case 0:                /* normal completion? */

    case -ECONNABORTED:        /* hardware forced ep reset */
    case -ECONNRESET:        /* request dequeued */
    case -ESHUTDOWN:        /* disconnect from host */
        if (ep == ss->out_ep)
        {
            memset(ss->data, 0, BUFLEN);
            memcpy(ss->data, req->buf, req->actual);
            ss->actual = req->actual;
        }
        break;

    case -EOVERFLOW:
    default:
    case -EREMOTEIO:    
        break;
    }
    //沒有繼續
    free_ep_req(ep, req);
    complete(&ss->gdt_completion);
}

static int gadget_transfer_open(struct inode *inode, struct file *filp)
{
    return 0;
}

static ssize_t gadget_transfer_read(struct file *filp, char __user * buf, size_t count, loff_t * f_pos)
{
    struct usb_request    *req;
    int ret;

    req = alloc_ep_req(ss->out_ep);
    if (!req)
    {
        ret = -ENOMEM;
        goto fail;
    }

    req->complete = source_sink_complete;

    ret = usb_ep_queue(ss->out_ep, req, GFP_ATOMIC);
    if (ret) {
        free_ep_req(ss->out_ep, req);

        goto fail;
    }

    wait_for_completion(&ss->gdt_completion);

    ss->actual = (count < ss->actual) ? count : ss->actual;
    if (copy_to_user (buf, ss->data, ss->actual)) //拷貝讀取的數據到用戶空間
    {
         ret = -EFAULT;
         goto fail;
    }

    return ss->actual;

fail:
    return ret;
}

static ssize_t gadget_transfer_write(struct file *filp, const char __user * buf, size_t count, loff_t * f_pos)
{
    struct usb_request    *req;
    int ret;

    req = alloc_ep_req(ss->in_ep);
    if (!req)
    {
        return -ENOMEM;
    }

    req->length = (count < BUFLEN) ? count : BUFLEN;

    if (copy_from_user (req->buf, buf, req->length)) //拷貝讀取的數據到用戶空間
    {
         ret = -EFAULT;
         goto fail;
    }



    req->complete = source_sink_complete;

    ret = usb_ep_queue(ss->in_ep, req, GFP_ATOMIC);
    if (ret) 
    {
        goto fail;
    }

    wait_for_completion(&ss->gdt_completion);

    return req->actual;

fail:
    free_ep_req(ss->in_ep, req);

    return ret;
}

static int gadget_transfer_release(struct inode *inode, struct file *filp)
{
    return 0;
}

static struct file_operations gadget_transfer_fops = {
  owner:THIS_MODULE,
  open:gadget_transfer_open,
  read:gadget_transfer_read,
  write:gadget_transfer_write,
  release:gadget_transfer_release,
};


static struct miscdevice gadget_transfer_misc = {
    MISC_DYNAMIC_MINOR,
    "gadget_transfer",
    &gadget_transfer_fops,
};

/*-------------------------------------------------------------------------*/

static int __init gadget_transfer_bind(struct usb_composite_dev *cdev)
{
    struct usb_gadget    *gadget = cdev->gadget;
    int            id;
    int ret = 0;

    ret = misc_register(&gadget_transfer_misc);
    if (ret)
    {
         goto fail_reg;
    }

    //各字符串描述符的引索
    id = usb_string_id(cdev);//這個東西之前有說過，就是cdev->next_string_id++返回，怕id衝突
    if (id < 0)
        return id;
    strings_dev[STRING_MANUFACTURER_IDX].id = id;
    device_desc.iManufacturer = id;

    id = usb_string_id(cdev);
    if (id < 0)
        return id;
    strings_dev[STRING_PRODUCT_IDX].id = id;
    device_desc.iProduct = id;

    id = usb_string_id(cdev);
    if (id < 0)
        return id;
    strings_dev[STRING_SERIAL_IDX].id = id;
    device_desc.iSerialNumber = id;

    sourcesink_add(cdev);

    device_desc.bcdDevice = cpu_to_le16(0x0200 + 0x12);
    
    snprintf(manufacturer, sizeof manufacturer, "%s %s with %s",
        init_utsname()->sysname, init_utsname()->release,
        gadget->name);

fail_reg:

    return 0;
}

static int gadget_transfer_unbind(struct usb_composite_dev *cdev)
{
    misc_deregister(&gadget_transfer_misc);

    return 0;
}

static struct usb_composite_driver gadget_transfer_driver = {
    .name        = "gadget_transfer",
    .dev        = &device_desc,
    .strings    = dev_strings,
    .max_speed    = USB_SPEED_SUPER,
    .unbind        = gadget_transfer_unbind,
};

MODULE_LICENSE("GPL");

static int __init init(void)
{
    return usb_composite_probe(&gadget_transfer_driver, gadget_transfer_bind);
}
module_init(init);

static void __exit cleanup(void)
{
    usb_composite_unregister(&gadget_transfer_driver);
}
module_exit(cleanup);

usb-skeleton.c //linux-2.6.18 就改了

//#define USB_SKEL_VENDOR_ID 0x0ff0
//#define USB_SKEL_PRODUCT_ID 0x0ff0

/*
 * USB Skeleton driver - 2.0
 *
 * Copyright (C) 2001-2004 Greg Kroah-Hartman ([email protected])
 *
 *    This program is free software; you can redistribute it and/or
 *    modify it under the terms of the GNU General Public License as
 *    published by the Free Software Foundation, version 2.
 *
 * This driver is based on the 2.6.3 version of drivers/usb/usb-skeleton.c 
 * but has been rewritten to be easy to read and use, as no locks are now
 * needed anymore.
 *
 */

#include <linux/kernel.h>
#include <linux/errno.h>
#include <linux/init.h>
#include <linux/slab.h>
#include <linux/module.h>
#include <linux/kref.h>
#include <asm/uaccess.h>
#include <linux/usb.h>

/* Define these values to match your devices */
#define USB_SKEL_VENDOR_ID    0x0ff0
#define USB_SKEL_PRODUCT_ID    0x0ff0

/* table of devices that work with this driver */
static struct usb_device_id skel_table [] = {
    { USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },
    { }                    /* Terminating entry */
};
MODULE_DEVICE_TABLE (usb, skel_table);


/* Get a minor range for your devices from the usb maintainer */
#define USB_SKEL_MINOR_BASE    192

/* our private defines. if this grows any larger, use your own .h file */
#define MAX_TRANSFER        ( PAGE_SIZE - 512 )
#define WRITES_IN_FLIGHT    8

/* Structure to hold all of our device specific stuff */
struct usb_skel {
    struct usb_device *    udev;            /* the usb device for this device */
    struct usb_interface *    interface;        /* the interface for this device */
    struct semaphore    limit_sem;        /* limiting the number of writes in progress */
    unsigned char *        bulk_in_buffer;        /* the buffer to receive data */
    size_t            bulk_in_size;        /* the size of the receive buffer */
    __u8            bulk_in_endpointAddr;    /* the address of the bulk in endpoint */
    __u8            bulk_out_endpointAddr;    /* the address of the bulk out endpoint */
    struct kref        kref;
};
#define to_skel_dev(d) container_of(d, struct usb_skel, kref)

static struct usb_driver skel_driver;

static void skel_delete(struct kref *kref)
{    
    struct usb_skel *dev = to_skel_dev(kref);

    usb_put_dev(dev->udev);
    kfree (dev->bulk_in_buffer);
    kfree (dev);
}

static int skel_open(struct inode *inode, struct file *file)
{
    struct usb_skel *dev;
    struct usb_interface *interface;
    int subminor;
    int retval = 0;

    subminor = iminor(inode);

    interface = usb_find_interface(&skel_driver, subminor);
    if (!interface) {
        err ("%s - error, can't find device for minor %d",
             __FUNCTION__, subminor);
        retval = -ENODEV;
        goto exit;
    }

    dev = usb_get_intfdata(interface);
    if (!dev) {
        retval = -ENODEV;
        goto exit;
    }

    /* increment our usage count for the device */
    kref_get(&dev->kref);

    /* save our object in the file's private structure */
    file->private_data = dev;

exit:
    return retval;
}

static int skel_release(struct inode *inode, struct file *file)
{
    struct usb_skel *dev;

    dev = (struct usb_skel *)file->private_data;
    if (dev == NULL)
        return -ENODEV;

    /* decrement the count on our device */
    kref_put(&dev->kref, skel_delete);
    return 0;
}

static ssize_t skel_read(struct file *file, char *buffer, size_t count, loff_t *ppos)
{
    struct usb_skel *dev;
    int retval = 0;
    int bytes_read;

    dev = (struct usb_skel *)file->private_data;
    
    /* do a blocking bulk read to get data from the device */
    retval = usb_bulk_msg(dev->udev,
                  usb_rcvbulkpipe(dev->udev, dev->bulk_in_endpointAddr),
                  dev->bulk_in_buffer,
                  min(dev->bulk_in_size, count),
                  &bytes_read, 10000);

    memset(buffer, 0, sizeof(buffer));

    /* if the read was successful, copy the data to userspace */
    if (!retval) {
        if (copy_to_user(buffer, dev->bulk_in_buffer, bytes_read))
            retval = -EFAULT;
        else
            retval = bytes_read;
    }

    return retval;
}

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

    dev = (struct usb_skel *)urb->context;

    /* 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;
    size_t writesize = min(count, (size_t)MAX_TRANSFER);

    dev = (struct usb_skel *)file->private_data;

    /* verify that we actually have some data to write */
    if (count == 0)
        goto exit;

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

    /* create a urb, and a buffer for it, and copy the data to the urb */
    urb = usb_alloc_urb(0, GFP_KERNEL);
    if (!urb) {
        retval = -ENOMEM;
        goto error;
    }

    buf = usb_buffer_alloc(dev->udev, writesize, GFP_KERNEL, &urb->transfer_dma);
    if (!buf) {
        retval = -ENOMEM;
        goto error;
    }

    if (copy_from_user(buf, user_buffer, writesize)) {
        retval = -EFAULT;
        goto error;
    }

    /* 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);
    urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;

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

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

exit:
    return writesize;

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

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

/* 
 * 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 = NULL;
    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 == NULL) {
        err("Out of memory");
        goto error;
    }
    kref_init(&dev->kref);
    sema_init(&dev->limit_sem, WRITES_IN_FLIGHT);

    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 &&
            ((endpoint->bEndpointAddress & USB_ENDPOINT_DIR_MASK)
                    == USB_DIR_IN) &&
            ((endpoint->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK)
                    == USB_ENDPOINT_XFER_BULK)) {
            /* 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;
            }
        }

        if (!dev->bulk_out_endpointAddr &&
            ((endpoint->bEndpointAddress & USB_ENDPOINT_DIR_MASK)
                    == USB_DIR_OUT) &&
            ((endpoint->bmAttributes & USB_ENDPOINT_XFERTYPE_MASK)
                    == USB_ENDPOINT_XFER_BULK)) {
            /* we found a bulk out endpoint */
            dev->bulk_out_endpointAddr = endpoint->bEndpointAddress;
        }
    }
    if (!(dev->bulk_in_endpointAddr && dev->bulk_out_endpointAddr)) {
        err("Could not find both bulk-in and bulk-out endpoints");
        goto error;
    }

    /* save our data pointer in this interface device */
    usb_set_intfdata(interface, dev);

    /* we can register the device now, as it is ready */
    retval = usb_register_dev(interface, &skel_class);
    if (retval) {
        /* something prevented us from registering this driver */
        err("Not able to get a minor for this device.");
        usb_set_intfdata(interface, NULL);
        goto error;
    }

    /* let the user know what node this device is now attached to */
    info("USB Skeleton device now attached to USBSkel-%d", interface->minor);
    return 0;

error:
    if (dev)
        kref_put(&dev->kref, skel_delete);
    return retval;
}

static void skel_disconnect(struct usb_interface *interface)
{
    struct usb_skel *dev;
    int minor = interface->minor;

    /* prevent skel_open() from racing skel_disconnect() */
    lock_kernel();

    dev = usb_get_intfdata(interface);
    usb_set_intfdata(interface, NULL);

    /* give back our minor */
    usb_deregister_dev(interface, &skel_class);

    unlock_kernel();

    /* decrement our usage count */
    kref_put(&dev->kref, skel_delete);

    info("USB Skeleton #%d now disconnected", minor);
}

static struct usb_driver skel_driver = {
    .name =        "skeleton",
    .probe =    skel_probe,
    .disconnect =    skel_disconnect,
    .id_table =    skel_table,
};

static int __init usb_skel_init(void)
{
    int result;

    /* register this driver with the USB subsystem */
    result = usb_register(&skel_driver);
    if (result)
        err("usb_register failed. Error number %d", result);

    return result;
}

static void __exit usb_skel_exit(void)
{
    /* deregister this driver with the USB subsystem */
    usb_deregister(&skel_driver);
}

module_init (usb_skel_init);
module_exit (usb_skel_exit);

MODULE_LICENSE("GPL");

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