SAFE public projects git trees. - safe/jmp/linux-2.6/blob - drivers/usb/usb-skeleton.c

   1 /*
   2  * USB Skeleton driver - 2.2
   3  *
   4  * Copyright (C) 2001-2004 Greg Kroah-Hartman (greg@kroah.com)
   5  *
   6  *      This program is free software; you can redistribute it and/or
   7  *      modify it under the terms of the GNU General Public License as
   8  *      published by the Free Software Foundation, version 2.
   9  *
  10  * This driver is based on the 2.6.3 version of drivers/usb/usb-skeleton.c
  11  * but has been rewritten to be easier to read and use.
  12  *
  13  */
  14
  15 #include <linux/kernel.h>
  16 #include <linux/errno.h>
  17 #include <linux/init.h>
  18 #include <linux/slab.h>
  19 #include <linux/module.h>
  20 #include <linux/kref.h>
  21 #include <asm/uaccess.h>
  22 #include <linux/usb.h>
  23 #include <linux/mutex.h>
  24
  25
  26 /* Define these values to match your devices */
  27 #define USB_SKEL_VENDOR_ID      0xfff0
  28 #define USB_SKEL_PRODUCT_ID     0xfff0
  29
  30 /* table of devices that work with this driver */
  31 static struct usb_device_id skel_table [] = {
  32         { USB_DEVICE(USB_SKEL_VENDOR_ID, USB_SKEL_PRODUCT_ID) },
  33         { }                                     /* Terminating entry */
  34 };
  35 MODULE_DEVICE_TABLE(usb, skel_table);
  36
  37
  38 /* Get a minor range for your devices from the usb maintainer */
  39 #define USB_SKEL_MINOR_BASE     192
  40
  41 /* our private defines. if this grows any larger, use your own .h file */
  42 #define MAX_TRANSFER            (PAGE_SIZE - 512)
  43 /* MAX_TRANSFER is chosen so that the VM is not stressed by
  44    allocations > PAGE_SIZE and the number of packets in a page
  45    is an integer 512 is the largest possible packet on EHCI */
  46 #define WRITES_IN_FLIGHT        8
  47 /* arbitrarily chosen */
  48
  49 /* Structure to hold all of our device specific stuff */
  50 struct usb_skel {
  51         struct usb_device       *udev;                  /* the usb device for this device */
  52         struct usb_interface    *interface;             /* the interface for this device */
  53         struct semaphore        limit_sem;              /* limiting the number of writes in progress */
  54         struct usb_anchor       submitted;              /* in case we need to retract our submissions */
  55         struct urb              *bulk_in_urb;           /* the urb to read data with */
  56         unsigned char           *bulk_in_buffer;        /* the buffer to receive data */
  57         size_t                  bulk_in_size;           /* the size of the receive buffer */
  58         size_t                  bulk_in_filled;         /* number of bytes in the buffer */
  59         size_t                  bulk_in_copied;         /* already copied to user space */
  60         __u8                    bulk_in_endpointAddr;   /* the address of the bulk in endpoint */
  61         __u8                    bulk_out_endpointAddr;  /* the address of the bulk out endpoint */
  62         int                     errors;                 /* the last request tanked */
  63         int                     open_count;             /* count the number of openers */
  64         bool                    ongoing_read;           /* a read is going on */
  65         bool                    processed_urb;          /* indicates we haven't processed the urb */
  66         spinlock_t              err_lock;               /* lock for errors */
  67         struct kref             kref;
  68         struct mutex            io_mutex;               /* synchronize I/O with disconnect */
  69         struct completion       bulk_in_completion;     /* to wait for an ongoing read */
  70 };
  71 #define to_skel_dev(d) container_of(d, struct usb_skel, kref)
  72
  73 static struct usb_driver skel_driver;
  74 static void skel_draw_down(struct usb_skel *dev);
  75
  76 static void skel_delete(struct kref *kref)
  77 {
  78         struct usb_skel *dev = to_skel_dev(kref);
  79
  80         usb_free_urb(dev->bulk_in_urb);
  81         usb_put_dev(dev->udev);
  82         kfree(dev->bulk_in_buffer);
  83         kfree(dev);
  84 }
  85
  86 static int skel_open(struct inode *inode, struct file *file)
  87 {
  88         struct usb_skel *dev;
  89         struct usb_interface *interface;
  90         int subminor;
  91         int retval = 0;
  92
  93         subminor = iminor(inode);
  94
  95         interface = usb_find_interface(&skel_driver, subminor);
  96         if (!interface) {
  97                 err ("%s - error, can't find device for minor %d",
  98                      __func__, subminor);
  99                 retval = -ENODEV;
 100                 goto exit;
 101         }
 102
 103         dev = usb_get_intfdata(interface);
 104         if (!dev) {
 105                 retval = -ENODEV;
 106                 goto exit;
 107         }
 108
 109         /* increment our usage count for the device */
 110         kref_get(&dev->kref);
 111
 112         /* lock the device to allow correctly handling errors
 113          * in resumption */
 114         mutex_lock(&dev->io_mutex);
 115
 116         if (!dev->open_count++) {
 117                 retval = usb_autopm_get_interface(interface);
 118                         if (retval) {
 119                                 dev->open_count--;
 120                                 mutex_unlock(&dev->io_mutex);
 121                                 kref_put(&dev->kref, skel_delete);
 122                                 goto exit;
 123                         }
 124         } /* else { //uncomment this block if you want exclusive open
 125                 retval = -EBUSY;
 126                 dev->open_count--;
 127                 mutex_unlock(&dev->io_mutex);
 128                 kref_put(&dev->kref, skel_delete);
 129                 goto exit;
 130         } */
 131         /* prevent the device from being autosuspended */
 132
 133         /* save our object in the file's private structure */
 134         file->private_data = dev;
 135         mutex_unlock(&dev->io_mutex);
 136
 137 exit:
 138         return retval;
 139 }
 140
 141 static int skel_release(struct inode *inode, struct file *file)
 142 {
 143         struct usb_skel *dev;
 144
 145         dev = (struct usb_skel *)file->private_data;
 146         if (dev == NULL)
 147                 return -ENODEV;
 148
 149         /* allow the device to be autosuspended */
 150         mutex_lock(&dev->io_mutex);
 151         if (!--dev->open_count && dev->interface)
 152                 usb_autopm_put_interface(dev->interface);
 153         mutex_unlock(&dev->io_mutex);
 154
 155         /* decrement the count on our device */
 156         kref_put(&dev->kref, skel_delete);
 157         return 0;
 158 }
 159
 160 static int skel_flush(struct file *file, fl_owner_t id)
 161 {
 162         struct usb_skel *dev;
 163         int res;
 164
 165         dev = (struct usb_skel *)file->private_data;
 166         if (dev == NULL)
 167                 return -ENODEV;
 168
 169         /* wait for io to stop */
 170         mutex_lock(&dev->io_mutex);
 171         skel_draw_down(dev);
 172
 173         /* read out errors, leave subsequent opens a clean slate */
 174         spin_lock_irq(&dev->err_lock);
 175         res = dev->errors ? (dev->errors == -EPIPE ? -EPIPE : -EIO) : 0;
 176         dev->errors = 0;
 177         spin_unlock_irq(&dev->err_lock);
 178
 179         mutex_unlock(&dev->io_mutex);
 180
 181         return res;
 182 }
 183
 184 static void skel_read_bulk_callback(struct urb *urb)
 185 {
 186         struct usb_skel *dev;
 187
 188         dev = urb->context;
 189
 190         spin_lock(&dev->err_lock);
 191         /* sync/async unlink faults aren't errors */
 192         if (urb->status) {
 193                 if(!(urb->status == -ENOENT ||
 194                     urb->status == -ECONNRESET ||
 195                     urb->status == -ESHUTDOWN))
 196                         err("%s - nonzero write bulk status received: %d",
 197                             __func__, urb->status);
 198
 199                 dev->errors = urb->status;
 200         } else {
 201                 dev->bulk_in_filled = urb->actual_length;
 202         }
 203         dev->ongoing_read = 0;
 204         spin_unlock(&dev->err_lock);
 205
 206         complete(&dev->bulk_in_completion);
 207 }
 208
 209 static int skel_do_read_io(struct usb_skel *dev, size_t count)
 210 {
 211         int rv;
 212
 213         /* prepare a read */
 214         usb_fill_bulk_urb(dev->bulk_in_urb,
 215                         dev->udev,
 216                         usb_rcvbulkpipe(dev->udev,
 217                                 dev->bulk_in_endpointAddr),
 218                         dev->bulk_in_buffer,
 219                         min(dev->bulk_in_size, count),
 220                         skel_read_bulk_callback,
 221                         dev);
 222         /* tell everybody to leave the URB alone */
 223         spin_lock_irq(&dev->err_lock);
 224         dev->ongoing_read = 1;
 225         spin_unlock_irq(&dev->err_lock);
 226
 227         /* do it */
 228         rv = usb_submit_urb(dev->bulk_in_urb, GFP_KERNEL);
 229         if (rv < 0) {
 230                 err("%s - failed submitting read urb, error %d",
 231                         __func__, rv);
 232                 dev->bulk_in_filled = 0;
 233                 rv = (rv == -ENOMEM) ? rv : -EIO;
 234                 spin_lock_irq(&dev->err_lock);
 235                 dev->ongoing_read = 0;
 236                 spin_unlock_irq(&dev->err_lock);
 237         }
 238
 239         return rv;
 240 }
 241
 242 static ssize_t skel_read(struct file *file, char *buffer, size_t count, loff_t *ppos)
 243 {
 244         struct usb_skel *dev;
 245         int rv;
 246         bool ongoing_io;
 247
 248         dev = (struct usb_skel *)file->private_data;
 249
 250         /* if we cannot read at all, return EOF */
 251         if (!dev->bulk_in_urb || !count)
 252                 return 0;
 253
 254         /* no concurrent readers */
 255         rv = mutex_lock_interruptible(&dev->io_mutex);
 256         if (rv < 0)
 257                 return rv;
 258
 259         if (!dev->interface) {          /* disconnect() was called */
 260                 rv = -ENODEV;
 261                 goto exit;
 262         }
 263
 264         /* if IO is under way, we must not touch things */
 265 retry:
 266         spin_lock_irq(&dev->err_lock);
 267         ongoing_io = dev->ongoing_read;
 268         spin_unlock_irq(&dev->err_lock);
 269
 270         if (ongoing_io) {
 271                 /* nonblocking IO shall not wait */
 272                 if (file->f_flags & O_NONBLOCK) {
 273                         rv = -EAGAIN;
 274                         goto exit;
 275                 }
 276                 /*
 277                  * IO may take forever
 278                  * hence wait in an interruptible state
 279                  */
 280                 rv = wait_for_completion_interruptible(&dev->bulk_in_completion);
 281                 if (rv < 0)
 282                         goto exit;
 283                 /*
 284                  * by waiting we also semiprocessed the urb
 285                  * we must finish now
 286                  */
 287                 dev->bulk_in_copied = 0;
 288                 dev->processed_urb = 1;
 289         }
 290
 291         if (!dev->processed_urb) {
 292                 /*
 293                  * the URB hasn't been processed
 294                  * do it now
 295                  */
 296                 wait_for_completion(&dev->bulk_in_completion);
 297                 dev->bulk_in_copied = 0;
 298                 dev->processed_urb = 1;
 299         }
 300
 301         /* errors must be reported */
 302         if ((rv = dev->errors) < 0) {
 303                 /* any error is reported once */
 304                 dev->errors = 0;
 305                 /* to preserve notifications about reset */
 306                 rv = (rv == -EPIPE) ? rv : -EIO;
 307                 /* no data to deliver */
 308                 dev->bulk_in_filled = 0;
 309                 /* report it */
 310                 goto exit;
 311         }
 312
 313         /*
 314          * if the buffer is filled we may satisfy the read
 315          * else we need to start IO
 316          */
 317
 318         if (dev->bulk_in_filled) {
 319                 /* we had read data */
 320                 size_t available = dev->bulk_in_filled - dev->bulk_in_copied;
 321                 size_t chunk = min(available, count);
 322
 323                 if (!available) {
 324                         /*
 325                          * all data has been used
 326                          * actual IO needs to be done
 327                          */
 328                         rv = skel_do_read_io(dev, count);
 329                         if (rv < 0)
 330                                 goto exit;
 331                         else
 332                                 goto retry;
 333                 }
 334                 /*
 335                  * data is available
 336                  * chunk tells us how much shall be copied
 337                  */
 338
 339                 if (copy_to_user(buffer,
 340                                  dev->bulk_in_buffer + dev->bulk_in_copied,
 341                                  chunk))
 342                         rv = -EFAULT;
 343                 else
 344                         rv = chunk;
 345
 346                 dev->bulk_in_copied += chunk;
 347
 348                 /*
 349                  * if we are asked for more than we have,
 350                  * we start IO but don't wait
 351                  */
 352                 if (available < count)
 353                         skel_do_read_io(dev, count - chunk);
 354         } else {
 355                 /* no data in the buffer */
 356                 rv = skel_do_read_io(dev, count);
 357                 if (rv < 0)
 358                         goto exit;
 359                 else if (!file->f_flags & O_NONBLOCK)
 360                         goto retry;
 361                 rv = -EAGAIN;
 362         }
 363 exit:
 364         mutex_unlock(&dev->io_mutex);
 365         return rv;
 366 }
 367
 368 static void skel_write_bulk_callback(struct urb *urb)
 369 {
 370         struct usb_skel *dev;
 371
 372         dev = urb->context;
 373
 374         /* sync/async unlink faults aren't errors */
 375         if (urb->status) {
 376                 if(!(urb->status == -ENOENT ||
 377                     urb->status == -ECONNRESET ||
 378                     urb->status == -ESHUTDOWN))
 379                         err("%s - nonzero write bulk status received: %d",
 380                             __func__, urb->status);
 381
 382                 spin_lock(&dev->err_lock);
 383                 dev->errors = urb->status;
 384                 spin_unlock(&dev->err_lock);
 385         }
 386
 387         /* free up our allocated buffer */
 388         usb_buffer_free(urb->dev, urb->transfer_buffer_length,
 389                         urb->transfer_buffer, urb->transfer_dma);
 390         up(&dev->limit_sem);
 391 }
 392
 393 static ssize_t skel_write(struct file *file, const char *user_buffer, size_t count, loff_t *ppos)
 394 {
 395         struct usb_skel *dev;
 396         int retval = 0;
 397         struct urb *urb = NULL;
 398         char *buf = NULL;
 399         size_t writesize = min(count, (size_t)MAX_TRANSFER);
 400
 401         dev = (struct usb_skel *)file->private_data;
 402
 403         /* verify that we actually have some data to write */
 404         if (count == 0)
 405                 goto exit;
 406
 407         /* limit the number of URBs in flight to stop a user from using up all RAM */
 408         if (!file->f_flags & O_NONBLOCK) {
 409                 if (down_interruptible(&dev->limit_sem)) {
 410                         retval = -ERESTARTSYS;
 411                         goto exit;
 412                 }
 413         } else {
 414                 if (down_trylock(&dev->limit_sem)) {
 415                         retval = -EAGAIN;
 416                         goto exit;
 417                 }
 418         }
 419
 420         spin_lock_irq(&dev->err_lock);
 421         if ((retval = dev->errors) < 0) {
 422                 /* any error is reported once */
 423                 dev->errors = 0;
 424                 /* to preserve notifications about reset */
 425                 retval = (retval == -EPIPE) ? retval : -EIO;
 426         }
 427         spin_unlock_irq(&dev->err_lock);
 428         if (retval < 0)
 429                 goto error;
 430
 431         /* create a urb, and a buffer for it, and copy the data to the urb */
 432         urb = usb_alloc_urb(0, GFP_KERNEL);
 433         if (!urb) {
 434                 retval = -ENOMEM;
 435                 goto error;
 436         }
 437
 438         buf = usb_buffer_alloc(dev->udev, writesize, GFP_KERNEL, &urb->transfer_dma);
 439         if (!buf) {
 440                 retval = -ENOMEM;
 441                 goto error;
 442         }
 443
 444         if (copy_from_user(buf, user_buffer, writesize)) {
 445                 retval = -EFAULT;
 446                 goto error;
 447         }
 448
 449         /* this lock makes sure we don't submit URBs to gone devices */
 450         mutex_lock(&dev->io_mutex);
 451         if (!dev->interface) {          /* disconnect() was called */
 452                 mutex_unlock(&dev->io_mutex);
 453                 retval = -ENODEV;
 454                 goto error;
 455         }
 456
 457         /* initialize the urb properly */
 458         usb_fill_bulk_urb(urb, dev->udev,
 459                           usb_sndbulkpipe(dev->udev, dev->bulk_out_endpointAddr),
 460                           buf, writesize, skel_write_bulk_callback, dev);
 461         urb->transfer_flags |= URB_NO_TRANSFER_DMA_MAP;
 462         usb_anchor_urb(urb, &dev->submitted);
 463
 464         /* send the data out the bulk port */
 465         retval = usb_submit_urb(urb, GFP_KERNEL);
 466         mutex_unlock(&dev->io_mutex);
 467         if (retval) {
 468                 err("%s - failed submitting write urb, error %d", __func__, retval);
 469                 goto error_unanchor;
 470         }
 471
 472         /* release our reference to this urb, the USB core will eventually free it entirely */
 473         usb_free_urb(urb);
 474
 475
 476         return writesize;
 477
 478 error_unanchor:
 479         usb_unanchor_urb(urb);
 480 error:
 481         if (urb) {
 482                 usb_buffer_free(dev->udev, writesize, buf, urb->transfer_dma);
 483                 usb_free_urb(urb);
 484         }
 485         up(&dev->limit_sem);
 486
 487 exit:
 488         return retval;
 489 }
 490
 491 static const struct file_operations skel_fops = {
 492         .owner =        THIS_MODULE,
 493         .read =         skel_read,
 494         .write =        skel_write,
 495         .open =         skel_open,
 496         .release =      skel_release,
 497         .flush =        skel_flush,
 498 };
 499
 500 /*
 501  * usb class driver info in order to get a minor number from the usb core,
 502  * and to have the device registered with the driver core
 503  */
 504 static struct usb_class_driver skel_class = {
 505         .name =         "skel%d",
 506         .fops =         &skel_fops,
 507         .minor_base =   USB_SKEL_MINOR_BASE,
 508 };
 509
 510 static int skel_probe(struct usb_interface *interface, const struct usb_device_id *id)
 511 {
 512         struct usb_skel *dev;
 513         struct usb_host_interface *iface_desc;
 514         struct usb_endpoint_descriptor *endpoint;
 515         size_t buffer_size;
 516         int i;
 517         int retval = -ENOMEM;
 518
 519         /* allocate memory for our device state and initialize it */
 520         dev = kzalloc(sizeof(*dev), GFP_KERNEL);
 521         if (!dev) {
 522                 err("Out of memory");
 523                 goto error;
 524         }
 525         kref_init(&dev->kref);
 526         sema_init(&dev->limit_sem, WRITES_IN_FLIGHT);
 527         mutex_init(&dev->io_mutex);
 528         spin_lock_init(&dev->err_lock);
 529         init_usb_anchor(&dev->submitted);
 530         init_completion(&dev->bulk_in_completion);
 531
 532         dev->udev = usb_get_dev(interface_to_usbdev(interface));
 533         dev->interface = interface;
 534
 535         /* set up the endpoint information */
 536         /* use only the first bulk-in and bulk-out endpoints */
 537         iface_desc = interface->cur_altsetting;
 538         for (i = 0; i < iface_desc->desc.bNumEndpoints; ++i) {
 539                 endpoint = &iface_desc->endpoint[i].desc;
 540
 541                 if (!dev->bulk_in_endpointAddr &&
 542                     usb_endpoint_is_bulk_in(endpoint)) {
 543                         /* we found a bulk in endpoint */
 544                         buffer_size = le16_to_cpu(endpoint->wMaxPacketSize);
 545                         dev->bulk_in_size = buffer_size;
 546                         dev->bulk_in_endpointAddr = endpoint->bEndpointAddress;
 547                         dev->bulk_in_buffer = kmalloc(buffer_size, GFP_KERNEL);
 548                         if (!dev->bulk_in_buffer) {
 549                                 err("Could not allocate bulk_in_buffer");
 550                                 goto error;
 551                         }
 552                         dev->bulk_in_urb = usb_alloc_urb(0, GFP_KERNEL);
 553                         if (!dev->bulk_in_urb) {
 554                                 err("Could not allocate bulk_in_urb");
 555                                 goto error;
 556                         }
 557                 }
 558
 559                 if (!dev->bulk_out_endpointAddr &&
 560                     usb_endpoint_is_bulk_out(endpoint)) {
 561                         /* we found a bulk out endpoint */
 562                         dev->bulk_out_endpointAddr = endpoint->bEndpointAddress;
 563                 }
 564         }
 565         if (!(dev->bulk_in_endpointAddr && dev->bulk_out_endpointAddr)) {
 566                 err("Could not find both bulk-in and bulk-out endpoints");
 567                 goto error;
 568         }
 569
 570         /* save our data pointer in this interface device */
 571         usb_set_intfdata(interface, dev);
 572
 573         /* we can register the device now, as it is ready */
 574         retval = usb_register_dev(interface, &skel_class);
 575         if (retval) {
 576                 /* something prevented us from registering this driver */
 577                 err("Not able to get a minor for this device.");
 578                 usb_set_intfdata(interface, NULL);
 579                 goto error;
 580         }
 581
 582         /* let the user know what node this device is now attached to */
 583         dev_info(&interface->dev,
 584                  "USB Skeleton device now attached to USBSkel-%d",
 585                  interface->minor);
 586         return 0;
 587
 588 error:
 589         if (dev)
 590                 /* this frees allocated memory */
 591                 kref_put(&dev->kref, skel_delete);
 592         return retval;
 593 }
 594
 595 static void skel_disconnect(struct usb_interface *interface)
 596 {
 597         struct usb_skel *dev;
 598         int minor = interface->minor;
 599
 600         dev = usb_get_intfdata(interface);
 601         usb_set_intfdata(interface, NULL);
 602
 603         /* give back our minor */
 604         usb_deregister_dev(interface, &skel_class);
 605
 606         /* prevent more I/O from starting */
 607         mutex_lock(&dev->io_mutex);
 608         dev->interface = NULL;
 609         mutex_unlock(&dev->io_mutex);
 610
 611         usb_kill_anchored_urbs(&dev->submitted);
 612
 613         /* decrement our usage count */
 614         kref_put(&dev->kref, skel_delete);
 615
 616         dev_info(&interface->dev, "USB Skeleton #%d now disconnected", minor);
 617 }
 618
 619 static void skel_draw_down(struct usb_skel *dev)
 620 {
 621         int time;
 622
 623         time = usb_wait_anchor_empty_timeout(&dev->submitted, 1000);
 624         if (!time)
 625                 usb_kill_anchored_urbs(&dev->submitted);
 626         usb_kill_urb(dev->bulk_in_urb);
 627 }
 628
 629 static int skel_suspend(struct usb_interface *intf, pm_message_t message)
 630 {
 631         struct usb_skel *dev = usb_get_intfdata(intf);
 632
 633         if (!dev)
 634                 return 0;
 635         skel_draw_down(dev);
 636         return 0;
 637 }
 638
 639 static int skel_resume (struct usb_interface *intf)
 640 {
 641         return 0;
 642 }
 643
 644 static int skel_pre_reset(struct usb_interface *intf)
 645 {
 646         struct usb_skel *dev = usb_get_intfdata(intf);
 647
 648         mutex_lock(&dev->io_mutex);
 649         skel_draw_down(dev);
 650
 651         return 0;
 652 }
 653
 654 static int skel_post_reset(struct usb_interface *intf)
 655 {
 656         struct usb_skel *dev = usb_get_intfdata(intf);
 657
 658         /* we are sure no URBs are active - no locking needed */
 659         dev->errors = -EPIPE;
 660         mutex_unlock(&dev->io_mutex);
 661
 662         return 0;
 663 }
 664
 665 static struct usb_driver skel_driver = {
 666         .name =         "skeleton",
 667         .probe =        skel_probe,
 668         .disconnect =   skel_disconnect,
 669         .suspend =      skel_suspend,
 670         .resume =       skel_resume,
 671         .pre_reset =    skel_pre_reset,
 672         .post_reset =   skel_post_reset,
 673         .id_table =     skel_table,
 674         .supports_autosuspend = 1,
 675 };
 676
 677 static int __init usb_skel_init(void)
 678 {
 679         int result;
 680
 681         /* register this driver with the USB subsystem */
 682         result = usb_register(&skel_driver);
 683         if (result)
 684                 err("usb_register failed. Error number %d", result);
 685
 686         return result;
 687 }
 688
 689 static void __exit usb_skel_exit(void)
 690 {
 691         /* deregister this driver with the USB subsystem */
 692         usb_deregister(&skel_driver);
 693 }
 694
 695 module_init(usb_skel_init);
 696 module_exit(usb_skel_exit);
 697
 698 MODULE_LICENSE("GPL");