drivers/uio/uio.c

   1 /*
   2  * drivers/uio/uio.c
   3  *
   4  * Copyright(C) 2005, Benedikt Spranger <b.spranger@linutronix.de>
   5  * Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
   6  * Copyright(C) 2006, Hans J. Koch <hjk@linutronix.de>
   7  * Copyright(C) 2006, Greg Kroah-Hartman <greg@kroah.com>
   8  *
   9  * Userspace IO
  10  *
  11  * Base Functions
  12  *
  13  * Licensed under the GPLv2 only.
  14  */
  15
  16 #include <linux/module.h>
  17 #include <linux/init.h>
  18 #include <linux/poll.h>
  19 #include <linux/device.h>
  20 #include <linux/mm.h>
  21 #include <linux/idr.h>
  22 #include <linux/string.h>
  23 #include <linux/kobject.h>
  24 #include <linux/uio_driver.h>
  25
  26 #define UIO_MAX_DEVICES 255
  27
  28 struct uio_device {
  29         struct module           *owner;
  30         struct device           *dev;
  31         int                     minor;
  32         atomic_t                event;
  33         struct fasync_struct    *async_queue;
  34         wait_queue_head_t       wait;
  35         int                     vma_count;
  36         struct uio_info         *info;
  37         struct kobject          *map_dir;
  38 };
  39
  40 static int uio_major;
  41 static DEFINE_IDR(uio_idr);
  42 static const struct file_operations uio_fops;
  43
  44 /* UIO class infrastructure */
  45 static struct uio_class {
  46         struct kref kref;
  47         struct class *class;
  48 } *uio_class;
  49
  50 /* Protect idr accesses */
  51 static DEFINE_MUTEX(minor_lock);
  52
  53 /*
  54  * attributes
  55  */
  56
  57 struct uio_map {
  58         struct kobject kobj;
  59         struct uio_mem *mem;
  60 };
  61 #define to_map(map) container_of(map, struct uio_map, kobj)
  62
  63 static ssize_t map_addr_show(struct uio_mem *mem, char *buf)
  64 {
  65         return sprintf(buf, "0x%lx\n", mem->addr);
  66 }
  67
  68 static ssize_t map_size_show(struct uio_mem *mem, char *buf)
  69 {
  70         return sprintf(buf, "0x%lx\n", mem->size);
  71 }
  72
  73 static ssize_t map_offset_show(struct uio_mem *mem, char *buf)
  74 {
  75         return sprintf(buf, "0x%lx\n", mem->addr & ~PAGE_MASK);
  76 }
  77
  78 struct uio_sysfs_entry {
  79         struct attribute attr;
  80         ssize_t (*show)(struct uio_mem *, char *);
  81         ssize_t (*store)(struct uio_mem *, const char *, size_t);
  82 };
  83
  84 static struct uio_sysfs_entry addr_attribute =
  85         __ATTR(addr, S_IRUGO, map_addr_show, NULL);
  86 static struct uio_sysfs_entry size_attribute =
  87         __ATTR(size, S_IRUGO, map_size_show, NULL);
  88 static struct uio_sysfs_entry offset_attribute =
  89         __ATTR(offset, S_IRUGO, map_offset_show, NULL);
  90
  91 static struct attribute *attrs[] = {
  92         &addr_attribute.attr,
  93         &size_attribute.attr,
  94         &offset_attribute.attr,
  95         NULL,   /* need to NULL terminate the list of attributes */
  96 };
  97
  98 static void map_release(struct kobject *kobj)
  99 {
 100         struct uio_map *map = to_map(kobj);
 101         kfree(map);
 102 }
 103
 104 static ssize_t map_type_show(struct kobject *kobj, struct attribute *attr,
 105                              char *buf)
 106 {
 107         struct uio_map *map = to_map(kobj);
 108         struct uio_mem *mem = map->mem;
 109         struct uio_sysfs_entry *entry;
 110
 111         entry = container_of(attr, struct uio_sysfs_entry, attr);
 112
 113         if (!entry->show)
 114                 return -EIO;
 115
 116         return entry->show(mem, buf);
 117 }
 118
 119 static struct sysfs_ops uio_sysfs_ops = {
 120         .show = map_type_show,
 121 };
 122
 123 static struct kobj_type map_attr_type = {
 124         .release        = map_release,
 125         .sysfs_ops      = &uio_sysfs_ops,
 126         .default_attrs  = attrs,
 127 };
 128
 129 static ssize_t show_name(struct device *dev,
 130                          struct device_attribute *attr, char *buf)
 131 {
 132         struct uio_device *idev = dev_get_drvdata(dev);
 133         if (idev)
 134                 return sprintf(buf, "%s\n", idev->info->name);
 135         else
 136                 return -ENODEV;
 137 }
 138 static DEVICE_ATTR(name, S_IRUGO, show_name, NULL);
 139
 140 static ssize_t show_version(struct device *dev,
 141                             struct device_attribute *attr, char *buf)
 142 {
 143         struct uio_device *idev = dev_get_drvdata(dev);
 144         if (idev)
 145                 return sprintf(buf, "%s\n", idev->info->version);
 146         else
 147                 return -ENODEV;
 148 }
 149 static DEVICE_ATTR(version, S_IRUGO, show_version, NULL);
 150
 151 static ssize_t show_event(struct device *dev,
 152                           struct device_attribute *attr, char *buf)
 153 {
 154         struct uio_device *idev = dev_get_drvdata(dev);
 155         if (idev)
 156                 return sprintf(buf, "%u\n",
 157                                 (unsigned int)atomic_read(&idev->event));
 158         else
 159                 return -ENODEV;
 160 }
 161 static DEVICE_ATTR(event, S_IRUGO, show_event, NULL);
 162
 163 static struct attribute *uio_attrs[] = {
 164         &dev_attr_name.attr,
 165         &dev_attr_version.attr,
 166         &dev_attr_event.attr,
 167         NULL,
 168 };
 169
 170 static struct attribute_group uio_attr_grp = {
 171         .attrs = uio_attrs,
 172 };
 173
 174 /*
 175  * device functions
 176  */
 177 static int uio_dev_add_attributes(struct uio_device *idev)
 178 {
 179         int ret;
 180         int mi;
 181         int map_found = 0;
 182         struct uio_mem *mem;
 183         struct uio_map *map;
 184
 185         ret = sysfs_create_group(&idev->dev->kobj, &uio_attr_grp);
 186         if (ret)
 187                 goto err_group;
 188
 189         for (mi = 0; mi < MAX_UIO_MAPS; mi++) {
 190                 mem = &idev->info->mem[mi];
 191                 if (mem->size == 0)
 192                         break;
 193                 if (!map_found) {
 194                         map_found = 1;
 195                         idev->map_dir = kobject_create_and_add("maps",
 196                                                         &idev->dev->kobj);
 197                         if (!idev->map_dir)
 198                                 goto err;
 199                 }
 200                 map = kzalloc(sizeof(*map), GFP_KERNEL);
 201                 if (!map)
 202                         goto err;
 203                 kobject_init(&map->kobj, &map_attr_type);
 204                 map->mem = mem;
 205                 mem->map = map;
 206                 ret = kobject_add(&map->kobj, idev->map_dir, "map%d", mi);
 207                 if (ret)
 208                         goto err;
 209                 ret = kobject_uevent(&map->kobj, KOBJ_ADD);
 210                 if (ret)
 211                         goto err;
 212         }
 213
 214         return 0;
 215
 216 err:
 217         for (mi--; mi>=0; mi--) {
 218                 mem = &idev->info->mem[mi];
 219                 map = mem->map;
 220                 kobject_put(&map->kobj);
 221         }
 222         kobject_put(idev->map_dir);
 223         sysfs_remove_group(&idev->dev->kobj, &uio_attr_grp);
 224 err_group:
 225         dev_err(idev->dev, "error creating sysfs files (%d)\n", ret);
 226         return ret;
 227 }
 228
 229 static void uio_dev_del_attributes(struct uio_device *idev)
 230 {
 231         int mi;
 232         struct uio_mem *mem;
 233         for (mi = 0; mi < MAX_UIO_MAPS; mi++) {
 234                 mem = &idev->info->mem[mi];
 235                 if (mem->size == 0)
 236                         break;
 237                 kobject_put(&mem->map->kobj);
 238         }
 239         kobject_put(idev->map_dir);
 240         sysfs_remove_group(&idev->dev->kobj, &uio_attr_grp);
 241 }
 242
 243 static int uio_get_minor(struct uio_device *idev)
 244 {
 245         int retval = -ENOMEM;
 246         int id;
 247
 248         mutex_lock(&minor_lock);
 249         if (idr_pre_get(&uio_idr, GFP_KERNEL) == 0)
 250                 goto exit;
 251
 252         retval = idr_get_new(&uio_idr, idev, &id);
 253         if (retval < 0) {
 254                 if (retval == -EAGAIN)
 255                         retval = -ENOMEM;
 256                 goto exit;
 257         }
 258         idev->minor = id & MAX_ID_MASK;
 259 exit:
 260         mutex_unlock(&minor_lock);
 261         return retval;
 262 }
 263
 264 static void uio_free_minor(struct uio_device *idev)
 265 {
 266         mutex_lock(&minor_lock);
 267         idr_remove(&uio_idr, idev->minor);
 268         mutex_unlock(&minor_lock);
 269 }
 270
 271 /**
 272  * uio_event_notify - trigger an interrupt event
 273  * @info: UIO device capabilities
 274  */
 275 void uio_event_notify(struct uio_info *info)
 276 {
 277         struct uio_device *idev = info->uio_dev;
 278
 279         atomic_inc(&idev->event);
 280         wake_up_interruptible(&idev->wait);
 281         kill_fasync(&idev->async_queue, SIGIO, POLL_IN);
 282 }
 283 EXPORT_SYMBOL_GPL(uio_event_notify);
 284
 285 /**
 286  * uio_interrupt - hardware interrupt handler
 287  * @irq: IRQ number, can be UIO_IRQ_CYCLIC for cyclic timer
 288  * @dev_id: Pointer to the devices uio_device structure
 289  */
 290 static irqreturn_t uio_interrupt(int irq, void *dev_id)
 291 {
 292         struct uio_device *idev = (struct uio_device *)dev_id;
 293         irqreturn_t ret = idev->info->handler(irq, idev->info);
 294
 295         if (ret == IRQ_HANDLED)
 296                 uio_event_notify(idev->info);
 297
 298         return ret;
 299 }
 300
 301 struct uio_listener {
 302         struct uio_device *dev;
 303         s32 event_count;
 304 };
 305
 306 static int uio_open(struct inode *inode, struct file *filep)
 307 {
 308         struct uio_device *idev;
 309         struct uio_listener *listener;
 310         int ret = 0;
 311
 312         mutex_lock(&minor_lock);
 313         idev = idr_find(&uio_idr, iminor(inode));
 314         mutex_unlock(&minor_lock);
 315         if (!idev) {
 316                 ret = -ENODEV;
 317                 goto out;
 318         }
 319
 320         if (!try_module_get(idev->owner)) {
 321                 ret = -ENODEV;
 322                 goto out;
 323         }
 324
 325         listener = kmalloc(sizeof(*listener), GFP_KERNEL);
 326         if (!listener) {
 327                 ret = -ENOMEM;
 328                 goto err_alloc_listener;
 329         }
 330
 331         listener->dev = idev;
 332         listener->event_count = atomic_read(&idev->event);
 333         filep->private_data = listener;
 334
 335         if (idev->info->open) {
 336                 ret = idev->info->open(idev->info, inode);
 337                 if (ret)
 338                         goto err_infoopen;
 339         }
 340         return 0;
 341
 342 err_infoopen:
 343         kfree(listener);
 344
 345 err_alloc_listener:
 346         module_put(idev->owner);
 347
 348 out:
 349         return ret;
 350 }
 351
 352 static int uio_fasync(int fd, struct file *filep, int on)
 353 {
 354         struct uio_listener *listener = filep->private_data;
 355         struct uio_device *idev = listener->dev;
 356
 357         return fasync_helper(fd, filep, on, &idev->async_queue);
 358 }
 359
 360 static int uio_release(struct inode *inode, struct file *filep)
 361 {
 362         int ret = 0;
 363         struct uio_listener *listener = filep->private_data;
 364         struct uio_device *idev = listener->dev;
 365
 366         if (idev->info->release)
 367                 ret = idev->info->release(idev->info, inode);
 368
 369         module_put(idev->owner);
 370         kfree(listener);
 371         return ret;
 372 }
 373
 374 static unsigned int uio_poll(struct file *filep, poll_table *wait)
 375 {
 376         struct uio_listener *listener = filep->private_data;
 377         struct uio_device *idev = listener->dev;
 378
 379         if (idev->info->irq == UIO_IRQ_NONE)
 380                 return -EIO;
 381
 382         poll_wait(filep, &idev->wait, wait);
 383         if (listener->event_count != atomic_read(&idev->event))
 384                 return POLLIN | POLLRDNORM;
 385         return 0;
 386 }
 387
 388 static ssize_t uio_read(struct file *filep, char __user *buf,
 389                         size_t count, loff_t *ppos)
 390 {
 391         struct uio_listener *listener = filep->private_data;
 392         struct uio_device *idev = listener->dev;
 393         DECLARE_WAITQUEUE(wait, current);
 394         ssize_t retval;
 395         s32 event_count;
 396
 397         if (idev->info->irq == UIO_IRQ_NONE)
 398                 return -EIO;
 399
 400         if (count != sizeof(s32))
 401                 return -EINVAL;
 402
 403         add_wait_queue(&idev->wait, &wait);
 404
 405         do {
 406                 set_current_state(TASK_INTERRUPTIBLE);
 407
 408                 event_count = atomic_read(&idev->event);
 409                 if (event_count != listener->event_count) {
 410                         if (copy_to_user(buf, &event_count, count))
 411                                 retval = -EFAULT;
 412                         else {
 413                                 listener->event_count = event_count;
 414                                 retval = count;
 415                         }
 416                         break;
 417                 }
 418
 419                 if (filep->f_flags & O_NONBLOCK) {
 420                         retval = -EAGAIN;
 421                         break;
 422                 }
 423
 424                 if (signal_pending(current)) {
 425                         retval = -ERESTARTSYS;
 426                         break;
 427                 }
 428                 schedule();
 429         } while (1);
 430
 431         __set_current_state(TASK_RUNNING);
 432         remove_wait_queue(&idev->wait, &wait);
 433
 434         return retval;
 435 }
 436
 437 static ssize_t uio_write(struct file *filep, const char __user *buf,
 438                         size_t count, loff_t *ppos)
 439 {
 440         struct uio_listener *listener = filep->private_data;
 441         struct uio_device *idev = listener->dev;
 442         ssize_t retval;
 443         s32 irq_on;
 444
 445         if (idev->info->irq == UIO_IRQ_NONE)
 446                 return -EIO;
 447
 448         if (count != sizeof(s32))
 449                 return -EINVAL;
 450
 451         if (!idev->info->irqcontrol)
 452                 return -ENOSYS;
 453
 454         if (copy_from_user(&irq_on, buf, count))
 455                 return -EFAULT;
 456
 457         retval = idev->info->irqcontrol(idev->info, irq_on);
 458
 459         return retval ? retval : sizeof(s32);
 460 }
 461
 462 static int uio_find_mem_index(struct vm_area_struct *vma)
 463 {
 464         int mi;
 465         struct uio_device *idev = vma->vm_private_data;
 466
 467         for (mi = 0; mi < MAX_UIO_MAPS; mi++) {
 468                 if (idev->info->mem[mi].size == 0)
 469                         return -1;
 470                 if (vma->vm_pgoff == mi)
 471                         return mi;
 472         }
 473         return -1;
 474 }
 475
 476 static void uio_vma_open(struct vm_area_struct *vma)
 477 {
 478         struct uio_device *idev = vma->vm_private_data;
 479         idev->vma_count++;
 480 }
 481
 482 static void uio_vma_close(struct vm_area_struct *vma)
 483 {
 484         struct uio_device *idev = vma->vm_private_data;
 485         idev->vma_count--;
 486 }
 487
 488 static int uio_vma_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
 489 {
 490         struct uio_device *idev = vma->vm_private_data;
 491         struct page *page;
 492         unsigned long offset;
 493
 494         int mi = uio_find_mem_index(vma);
 495         if (mi < 0)
 496                 return VM_FAULT_SIGBUS;
 497
 498         /*
 499          * We need to subtract mi because userspace uses offset = N*PAGE_SIZE
 500          * to use mem[N].
 501          */
 502         offset = (vmf->pgoff - mi) << PAGE_SHIFT;
 503
 504         if (idev->info->mem[mi].memtype == UIO_MEM_LOGICAL)
 505                 page = virt_to_page(idev->info->mem[mi].addr + offset);
 506         else
 507                 page = vmalloc_to_page((void *)idev->info->mem[mi].addr
 508                                                         + offset);
 509         get_page(page);
 510         vmf->page = page;
 511         return 0;
 512 }
 513
 514 static struct vm_operations_struct uio_vm_ops = {
 515         .open = uio_vma_open,
 516         .close = uio_vma_close,
 517         .fault = uio_vma_fault,
 518 };
 519
 520 static int uio_mmap_physical(struct vm_area_struct *vma)
 521 {
 522         struct uio_device *idev = vma->vm_private_data;
 523         int mi = uio_find_mem_index(vma);
 524         if (mi < 0)
 525                 return -EINVAL;
 526
 527         vma->vm_flags |= VM_IO | VM_RESERVED;
 528
 529         vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
 530
 531         return remap_pfn_range(vma,
 532                                vma->vm_start,
 533                                idev->info->mem[mi].addr >> PAGE_SHIFT,
 534                                vma->vm_end - vma->vm_start,
 535                                vma->vm_page_prot);
 536 }
 537
 538 static int uio_mmap_logical(struct vm_area_struct *vma)
 539 {
 540         vma->vm_flags |= VM_RESERVED;
 541         vma->vm_ops = &uio_vm_ops;
 542         uio_vma_open(vma);
 543         return 0;
 544 }
 545
 546 static int uio_mmap(struct file *filep, struct vm_area_struct *vma)
 547 {
 548         struct uio_listener *listener = filep->private_data;
 549         struct uio_device *idev = listener->dev;
 550         int mi;
 551         unsigned long requested_pages, actual_pages;
 552         int ret = 0;
 553
 554         if (vma->vm_end < vma->vm_start)
 555                 return -EINVAL;
 556
 557         vma->vm_private_data = idev;
 558
 559         mi = uio_find_mem_index(vma);
 560         if (mi < 0)
 561                 return -EINVAL;
 562
 563         requested_pages = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
 564         actual_pages = (idev->info->mem[mi].size + PAGE_SIZE -1) >> PAGE_SHIFT;
 565         if (requested_pages > actual_pages)
 566                 return -EINVAL;
 567
 568         if (idev->info->mmap) {
 569                 ret = idev->info->mmap(idev->info, vma);
 570                 return ret;
 571         }
 572
 573         switch (idev->info->mem[mi].memtype) {
 574                 case UIO_MEM_PHYS:
 575                         return uio_mmap_physical(vma);
 576                 case UIO_MEM_LOGICAL:
 577                 case UIO_MEM_VIRTUAL:
 578                         return uio_mmap_logical(vma);
 579                 default:
 580                         return -EINVAL;
 581         }
 582 }
 583
 584 static const struct file_operations uio_fops = {
 585         .owner          = THIS_MODULE,
 586         .open           = uio_open,
 587         .release        = uio_release,
 588         .read           = uio_read,
 589         .write          = uio_write,
 590         .mmap           = uio_mmap,
 591         .poll           = uio_poll,
 592         .fasync         = uio_fasync,
 593 };
 594
 595 static int uio_major_init(void)
 596 {
 597         uio_major = register_chrdev(0, "uio", &uio_fops);
 598         if (uio_major < 0)
 599                 return uio_major;
 600         return 0;
 601 }
 602
 603 static void uio_major_cleanup(void)
 604 {
 605         unregister_chrdev(uio_major, "uio");
 606 }
 607
 608 static int init_uio_class(void)
 609 {
 610         int ret = 0;
 611
 612         if (uio_class != NULL) {
 613                 kref_get(&uio_class->kref);
 614                 goto exit;
 615         }
 616
 617         /* This is the first time in here, set everything up properly */
 618         ret = uio_major_init();
 619         if (ret)
 620                 goto exit;
 621
 622         uio_class = kzalloc(sizeof(*uio_class), GFP_KERNEL);
 623         if (!uio_class) {
 624                 ret = -ENOMEM;
 625                 goto err_kzalloc;
 626         }
 627
 628         kref_init(&uio_class->kref);
 629         uio_class->class = class_create(THIS_MODULE, "uio");
 630         if (IS_ERR(uio_class->class)) {
 631                 ret = IS_ERR(uio_class->class);
 632                 printk(KERN_ERR "class_create failed for uio\n");
 633                 goto err_class_create;
 634         }
 635         return 0;
 636
 637 err_class_create:
 638         kfree(uio_class);
 639         uio_class = NULL;
 640 err_kzalloc:
 641         uio_major_cleanup();
 642 exit:
 643         return ret;
 644 }
 645
 646 static void release_uio_class(struct kref *kref)
 647 {
 648         /* Ok, we cheat as we know we only have one uio_class */
 649         class_destroy(uio_class->class);
 650         kfree(uio_class);
 651         uio_major_cleanup();
 652         uio_class = NULL;
 653 }
 654
 655 static void uio_class_destroy(void)
 656 {
 657         if (uio_class)
 658                 kref_put(&uio_class->kref, release_uio_class);
 659 }
 660
 661 /**
 662  * uio_register_device - register a new userspace IO device
 663  * @owner:      module that creates the new device
 664  * @parent:     parent device
 665  * @info:       UIO device capabilities
 666  *
 667  * returns zero on success or a negative error code.
 668  */
 669 int __uio_register_device(struct module *owner,
 670                           struct device *parent,
 671                           struct uio_info *info)
 672 {
 673         struct uio_device *idev;
 674         int ret = 0;
 675
 676         if (!parent || !info || !info->name || !info->version)
 677                 return -EINVAL;
 678
 679         info->uio_dev = NULL;
 680
 681         ret = init_uio_class();
 682         if (ret)
 683                 return ret;
 684
 685         idev = kzalloc(sizeof(*idev), GFP_KERNEL);
 686         if (!idev) {
 687                 ret = -ENOMEM;
 688                 goto err_kzalloc;
 689         }
 690
 691         idev->owner = owner;
 692         idev->info = info;
 693         init_waitqueue_head(&idev->wait);
 694         atomic_set(&idev->event, 0);
 695
 696         ret = uio_get_minor(idev);
 697         if (ret)
 698                 goto err_get_minor;
 699
 700         idev->dev = device_create(uio_class->class, parent,
 701                                   MKDEV(uio_major, idev->minor), idev,
 702                                   "uio%d", idev->minor);
 703         if (IS_ERR(idev->dev)) {
 704                 printk(KERN_ERR "UIO: device register failed\n");
 705                 ret = PTR_ERR(idev->dev);
 706                 goto err_device_create;
 707         }
 708
 709         ret = uio_dev_add_attributes(idev);
 710         if (ret)
 711                 goto err_uio_dev_add_attributes;
 712
 713         info->uio_dev = idev;
 714
 715         if (idev->info->irq >= 0) {
 716                 ret = request_irq(idev->info->irq, uio_interrupt,
 717                                   idev->info->irq_flags, idev->info->name, idev);
 718                 if (ret)
 719                         goto err_request_irq;
 720         }
 721
 722         return 0;
 723
 724 err_request_irq:
 725         uio_dev_del_attributes(idev);
 726 err_uio_dev_add_attributes:
 727         device_destroy(uio_class->class, MKDEV(uio_major, idev->minor));
 728 err_device_create:
 729         uio_free_minor(idev);
 730 err_get_minor:
 731         kfree(idev);
 732 err_kzalloc:
 733         uio_class_destroy();
 734         return ret;
 735 }
 736 EXPORT_SYMBOL_GPL(__uio_register_device);
 737
 738 /**
 739  * uio_unregister_device - unregister a industrial IO device
 740  * @info:       UIO device capabilities
 741  *
 742  */
 743 void uio_unregister_device(struct uio_info *info)
 744 {
 745         struct uio_device *idev;
 746
 747         if (!info || !info->uio_dev)
 748                 return;
 749
 750         idev = info->uio_dev;
 751
 752         uio_free_minor(idev);
 753
 754         if (info->irq >= 0)
 755                 free_irq(info->irq, idev);
 756
 757         uio_dev_del_attributes(idev);
 758
 759         dev_set_drvdata(idev->dev, NULL);
 760         device_destroy(uio_class->class, MKDEV(uio_major, idev->minor));
 761         kfree(idev);
 762         uio_class_destroy();
 763
 764         return;
 765 }
 766 EXPORT_SYMBOL_GPL(uio_unregister_device);
 767
 768 static int __init uio_init(void)
 769 {
 770         return 0;
 771 }
 772
 773 static void __exit uio_exit(void)
 774 {
 775 }
 776
 777 module_init(uio_init)
 778 module_exit(uio_exit)
 779 MODULE_LICENSE("GPL v2");