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