drivers/i2c/i2c-dev.c

   1 /*
   2     i2c-dev.c - i2c-bus driver, char device interface
   3
   4     Copyright (C) 1995-97 Simon G. Vogl
   5     Copyright (C) 1998-99 Frodo Looijaard <frodol@dds.nl>
   6     Copyright (C) 2003 Greg Kroah-Hartman <greg@kroah.com>
   7
   8     This program is free software; you can redistribute it and/or modify
   9     it under the terms of the GNU General Public License as published by
  10     the Free Software Foundation; either version 2 of the License, or
  11     (at your option) any later version.
  12
  13     This program is distributed in the hope that it will be useful,
  14     but WITHOUT ANY WARRANTY; without even the implied warranty of
  15     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16     GNU General Public License for more details.
  17
  18     You should have received a copy of the GNU General Public License
  19     along with this program; if not, write to the Free Software
  20     Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21 */
  22
  23 /* Note that this is a complete rewrite of Simon Vogl's i2c-dev module.
  24    But I have used so much of his original code and ideas that it seems
  25    only fair to recognize him as co-author -- Frodo */
  26
  27 /* The I2C_RDWR ioctl code is written by Kolja Waschk <waschk@telos.de> */
  28
  29 #include <linux/kernel.h>
  30 #include <linux/module.h>
  31 #include <linux/fs.h>
  32 #include <linux/slab.h>
  33 #include <linux/init.h>
  34 #include <linux/list.h>
  35 #include <linux/i2c.h>
  36 #include <linux/i2c-dev.h>
  37 #include <linux/jiffies.h>
  38 #include <linux/uaccess.h>
  39
  40 static struct i2c_driver i2cdev_driver;
  41
  42 /*
  43  * An i2c_dev represents an i2c_adapter ... an I2C or SMBus master, not a
  44  * slave (i2c_client) with which messages will be exchanged.  It's coupled
  45  * with a character special file which is accessed by user mode drivers.
  46  *
  47  * The list of i2c_dev structures is parallel to the i2c_adapter lists
  48  * maintained by the driver model, and is updated using notifications
  49  * delivered to the i2cdev_driver.
  50  */
  51 struct i2c_dev {
  52         struct list_head list;
  53         struct i2c_adapter *adap;
  54         struct device *dev;
  55 };
  56
  57 #define I2C_MINORS      256
  58 static LIST_HEAD(i2c_dev_list);
  59 static DEFINE_SPINLOCK(i2c_dev_list_lock);
  60
  61 static struct i2c_dev *i2c_dev_get_by_minor(unsigned index)
  62 {
  63         struct i2c_dev *i2c_dev;
  64
  65         spin_lock(&i2c_dev_list_lock);
  66         list_for_each_entry(i2c_dev, &i2c_dev_list, list) {
  67                 if (i2c_dev->adap->nr == index)
  68                         goto found;
  69         }
  70         i2c_dev = NULL;
  71 found:
  72         spin_unlock(&i2c_dev_list_lock);
  73         return i2c_dev;
  74 }
  75
  76 static struct i2c_dev *get_free_i2c_dev(struct i2c_adapter *adap)
  77 {
  78         struct i2c_dev *i2c_dev;
  79
  80         if (adap->nr >= I2C_MINORS) {
  81                 printk(KERN_ERR "i2c-dev: Out of device minors (%d)\n",
  82                        adap->nr);
  83                 return ERR_PTR(-ENODEV);
  84         }
  85
  86         i2c_dev = kzalloc(sizeof(*i2c_dev), GFP_KERNEL);
  87         if (!i2c_dev)
  88                 return ERR_PTR(-ENOMEM);
  89         i2c_dev->adap = adap;
  90
  91         spin_lock(&i2c_dev_list_lock);
  92         list_add_tail(&i2c_dev->list, &i2c_dev_list);
  93         spin_unlock(&i2c_dev_list_lock);
  94         return i2c_dev;
  95 }
  96
  97 static void return_i2c_dev(struct i2c_dev *i2c_dev)
  98 {
  99         spin_lock(&i2c_dev_list_lock);
 100         list_del(&i2c_dev->list);
 101         spin_unlock(&i2c_dev_list_lock);
 102         kfree(i2c_dev);
 103 }
 104
 105 static ssize_t show_adapter_name(struct device *dev,
 106                                  struct device_attribute *attr, char *buf)
 107 {
 108         struct i2c_dev *i2c_dev = i2c_dev_get_by_minor(MINOR(dev->devt));
 109
 110         if (!i2c_dev)
 111                 return -ENODEV;
 112         return sprintf(buf, "%s\n", i2c_dev->adap->name);
 113 }
 114 static DEVICE_ATTR(name, S_IRUGO, show_adapter_name, NULL);
 115
 116 /* ------------------------------------------------------------------------- */
 117
 118 /*
 119  * After opening an instance of this character special file, a file
 120  * descriptor starts out associated only with an i2c_adapter (and bus).
 121  *
 122  * Using the I2C_RDWR ioctl(), you can then *immediately* issue i2c_msg
 123  * traffic to any devices on the bus used by that adapter.  That's because
 124  * the i2c_msg vectors embed all the addressing information they need, and
 125  * are submitted directly to an i2c_adapter.  However, SMBus-only adapters
 126  * don't support that interface.
 127  *
 128  * To use read()/write() system calls on that file descriptor, or to use
 129  * SMBus interfaces (and work with SMBus-only hosts!), you must first issue
 130  * an I2C_SLAVE (or I2C_SLAVE_FORCE) ioctl.  That configures an anonymous
 131  * (never registered) i2c_client so it holds the addressing information
 132  * needed by those system calls and by this SMBus interface.
 133  */
 134
 135 static ssize_t i2cdev_read(struct file *file, char __user *buf, size_t count,
 136                 loff_t *offset)
 137 {
 138         char *tmp;
 139         int ret;
 140
 141         struct i2c_client *client = file->private_data;
 142
 143         if (count > 8192)
 144                 count = 8192;
 145
 146         tmp = kmalloc(count, GFP_KERNEL);
 147         if (tmp == NULL)
 148                 return -ENOMEM;
 149
 150         pr_debug("i2c-dev: i2c-%d reading %zu bytes.\n",
 151                 iminor(file->f_path.dentry->d_inode), count);
 152
 153         ret = i2c_master_recv(client, tmp, count);
 154         if (ret >= 0)
 155                 ret = copy_to_user(buf, tmp, count) ? -EFAULT : ret;
 156         kfree(tmp);
 157         return ret;
 158 }
 159
 160 static ssize_t i2cdev_write(struct file *file, const char __user *buf,
 161                 size_t count, loff_t *offset)
 162 {
 163         int ret;
 164         char *tmp;
 165         struct i2c_client *client = file->private_data;
 166
 167         if (count > 8192)
 168                 count = 8192;
 169
 170         tmp = kmalloc(count, GFP_KERNEL);
 171         if (tmp == NULL)
 172                 return -ENOMEM;
 173         if (copy_from_user(tmp, buf, count)) {
 174                 kfree(tmp);
 175                 return -EFAULT;
 176         }
 177
 178         pr_debug("i2c-dev: i2c-%d writing %zu bytes.\n",
 179                 iminor(file->f_path.dentry->d_inode), count);
 180
 181         ret = i2c_master_send(client, tmp, count);
 182         kfree(tmp);
 183         return ret;
 184 }
 185
 186 static int i2cdev_check(struct device *dev, void *addrp)
 187 {
 188         struct i2c_client *client = i2c_verify_client(dev);
 189
 190         if (!client || client->addr != *(unsigned int *)addrp)
 191                 return 0;
 192
 193         return dev->driver ? -EBUSY : 0;
 194 }
 195
 196 /* This address checking function differs from the one in i2c-core
 197    in that it considers an address with a registered device, but no
 198    driver bound to it, as NOT busy. */
 199 static int i2cdev_check_addr(struct i2c_adapter *adapter, unsigned int addr)
 200 {
 201         return device_for_each_child(&adapter->dev, &addr, i2cdev_check);
 202 }
 203
 204 static noinline int i2cdev_ioctl_rdrw(struct i2c_client *client,
 205                 unsigned long arg)
 206 {
 207         struct i2c_rdwr_ioctl_data rdwr_arg;
 208         struct i2c_msg *rdwr_pa;
 209         u8 __user **data_ptrs;
 210         int i, res;
 211
 212         if (copy_from_user(&rdwr_arg,
 213                            (struct i2c_rdwr_ioctl_data __user *)arg,
 214                            sizeof(rdwr_arg)))
 215                 return -EFAULT;
 216
 217         /* Put an arbitrary limit on the number of messages that can
 218          * be sent at once */
 219         if (rdwr_arg.nmsgs > I2C_RDRW_IOCTL_MAX_MSGS)
 220                 return -EINVAL;
 221
 222         rdwr_pa = (struct i2c_msg *)
 223                 kmalloc(rdwr_arg.nmsgs * sizeof(struct i2c_msg),
 224                 GFP_KERNEL);
 225         if (!rdwr_pa)
 226                 return -ENOMEM;
 227
 228         if (copy_from_user(rdwr_pa, rdwr_arg.msgs,
 229                            rdwr_arg.nmsgs * sizeof(struct i2c_msg))) {
 230                 kfree(rdwr_pa);
 231                 return -EFAULT;
 232         }
 233
 234         data_ptrs = kmalloc(rdwr_arg.nmsgs * sizeof(u8 __user *), GFP_KERNEL);
 235         if (data_ptrs == NULL) {
 236                 kfree(rdwr_pa);
 237                 return -ENOMEM;
 238         }
 239
 240         res = 0;
 241         for (i = 0; i < rdwr_arg.nmsgs; i++) {
 242                 /* Limit the size of the message to a sane amount;
 243                  * and don't let length change either. */
 244                 if ((rdwr_pa[i].len > 8192) ||
 245                     (rdwr_pa[i].flags & I2C_M_RECV_LEN)) {
 246                         res = -EINVAL;
 247                         break;
 248                 }
 249                 data_ptrs[i] = (u8 __user *)rdwr_pa[i].buf;
 250                 rdwr_pa[i].buf = kmalloc(rdwr_pa[i].len, GFP_KERNEL);
 251                 if (rdwr_pa[i].buf == NULL) {
 252                         res = -ENOMEM;
 253                         break;
 254                 }
 255                 if (copy_from_user(rdwr_pa[i].buf, data_ptrs[i],
 256                                    rdwr_pa[i].len)) {
 257                                 ++i; /* Needs to be kfreed too */
 258                                 res = -EFAULT;
 259                         break;
 260                 }
 261         }
 262         if (res < 0) {
 263                 int j;
 264                 for (j = 0; j < i; ++j)
 265                         kfree(rdwr_pa[j].buf);
 266                 kfree(data_ptrs);
 267                 kfree(rdwr_pa);
 268                 return res;
 269         }
 270
 271         res = i2c_transfer(client->adapter, rdwr_pa, rdwr_arg.nmsgs);
 272         while (i-- > 0) {
 273                 if (res >= 0 && (rdwr_pa[i].flags & I2C_M_RD)) {
 274                         if (copy_to_user(data_ptrs[i], rdwr_pa[i].buf,
 275                                          rdwr_pa[i].len))
 276                                 res = -EFAULT;
 277                 }
 278                 kfree(rdwr_pa[i].buf);
 279         }
 280         kfree(data_ptrs);
 281         kfree(rdwr_pa);
 282         return res;
 283 }
 284
 285 static noinline int i2cdev_ioctl_smbus(struct i2c_client *client,
 286                 unsigned long arg)
 287 {
 288         struct i2c_smbus_ioctl_data data_arg;
 289         union i2c_smbus_data temp;
 290         int datasize, res;
 291
 292         if (copy_from_user(&data_arg,
 293                            (struct i2c_smbus_ioctl_data __user *) arg,
 294                            sizeof(struct i2c_smbus_ioctl_data)))
 295                 return -EFAULT;
 296         if ((data_arg.size != I2C_SMBUS_BYTE) &&
 297             (data_arg.size != I2C_SMBUS_QUICK) &&
 298             (data_arg.size != I2C_SMBUS_BYTE_DATA) &&
 299             (data_arg.size != I2C_SMBUS_WORD_DATA) &&
 300             (data_arg.size != I2C_SMBUS_PROC_CALL) &&
 301             (data_arg.size != I2C_SMBUS_BLOCK_DATA) &&
 302             (data_arg.size != I2C_SMBUS_I2C_BLOCK_BROKEN) &&
 303             (data_arg.size != I2C_SMBUS_I2C_BLOCK_DATA) &&
 304             (data_arg.size != I2C_SMBUS_BLOCK_PROC_CALL)) {
 305                 dev_dbg(&client->adapter->dev,
 306                         "size out of range (%x) in ioctl I2C_SMBUS.\n",
 307                         data_arg.size);
 308                 return -EINVAL;
 309         }
 310         /* Note that I2C_SMBUS_READ and I2C_SMBUS_WRITE are 0 and 1,
 311            so the check is valid if size==I2C_SMBUS_QUICK too. */
 312         if ((data_arg.read_write != I2C_SMBUS_READ) &&
 313             (data_arg.read_write != I2C_SMBUS_WRITE)) {
 314                 dev_dbg(&client->adapter->dev,
 315                         "read_write out of range (%x) in ioctl I2C_SMBUS.\n",
 316                         data_arg.read_write);
 317                 return -EINVAL;
 318         }
 319
 320         /* Note that command values are always valid! */
 321
 322         if ((data_arg.size == I2C_SMBUS_QUICK) ||
 323             ((data_arg.size == I2C_SMBUS_BYTE) &&
 324             (data_arg.read_write == I2C_SMBUS_WRITE)))
 325                 /* These are special: we do not use data */
 326                 return i2c_smbus_xfer(client->adapter, client->addr,
 327                                       client->flags, data_arg.read_write,
 328                                       data_arg.command, data_arg.size, NULL);
 329
 330         if (data_arg.data == NULL) {
 331                 dev_dbg(&client->adapter->dev,
 332                         "data is NULL pointer in ioctl I2C_SMBUS.\n");
 333                 return -EINVAL;
 334         }
 335
 336         if ((data_arg.size == I2C_SMBUS_BYTE_DATA) ||
 337             (data_arg.size == I2C_SMBUS_BYTE))
 338                 datasize = sizeof(data_arg.data->byte);
 339         else if ((data_arg.size == I2C_SMBUS_WORD_DATA) ||
 340                  (data_arg.size == I2C_SMBUS_PROC_CALL))
 341                 datasize = sizeof(data_arg.data->word);
 342         else /* size == smbus block, i2c block, or block proc. call */
 343                 datasize = sizeof(data_arg.data->block);
 344
 345         if ((data_arg.size == I2C_SMBUS_PROC_CALL) ||
 346             (data_arg.size == I2C_SMBUS_BLOCK_PROC_CALL) ||
 347             (data_arg.size == I2C_SMBUS_I2C_BLOCK_DATA) ||
 348             (data_arg.read_write == I2C_SMBUS_WRITE)) {
 349                 if (copy_from_user(&temp, data_arg.data, datasize))
 350                         return -EFAULT;
 351         }
 352         if (data_arg.size == I2C_SMBUS_I2C_BLOCK_BROKEN) {
 353                 /* Convert old I2C block commands to the new
 354                    convention. This preserves binary compatibility. */
 355                 data_arg.size = I2C_SMBUS_I2C_BLOCK_DATA;
 356                 if (data_arg.read_write == I2C_SMBUS_READ)
 357                         temp.block[0] = I2C_SMBUS_BLOCK_MAX;
 358         }
 359         res = i2c_smbus_xfer(client->adapter, client->addr, client->flags,
 360               data_arg.read_write, data_arg.command, data_arg.size, &temp);
 361         if (!res && ((data_arg.size == I2C_SMBUS_PROC_CALL) ||
 362                      (data_arg.size == I2C_SMBUS_BLOCK_PROC_CALL) ||
 363                      (data_arg.read_write == I2C_SMBUS_READ))) {
 364                 if (copy_to_user(data_arg.data, &temp, datasize))
 365                         return -EFAULT;
 366         }
 367         return res;
 368 }
 369
 370 static long i2cdev_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
 371 {
 372         struct i2c_client *client = file->private_data;
 373         unsigned long funcs;
 374
 375         dev_dbg(&client->adapter->dev, "ioctl, cmd=0x%02x, arg=0x%02lx\n",
 376                 cmd, arg);
 377
 378         switch (cmd) {
 379         case I2C_SLAVE:
 380         case I2C_SLAVE_FORCE:
 381                 /* NOTE:  devices set up to work with "new style" drivers
 382                  * can't use I2C_SLAVE, even when the device node is not
 383                  * bound to a driver.  Only I2C_SLAVE_FORCE will work.
 384                  *
 385                  * Setting the PEC flag here won't affect kernel drivers,
 386                  * which will be using the i2c_client node registered with
 387                  * the driver model core.  Likewise, when that client has
 388                  * the PEC flag already set, the i2c-dev driver won't see
 389                  * (or use) this setting.
 390                  */
 391                 if ((arg > 0x3ff) ||
 392                     (((client->flags & I2C_M_TEN) == 0) && arg > 0x7f))
 393                         return -EINVAL;
 394                 if (cmd == I2C_SLAVE && i2cdev_check_addr(client->adapter, arg))
 395                         return -EBUSY;
 396                 /* REVISIT: address could become busy later */
 397                 client->addr = arg;
 398                 return 0;
 399         case I2C_TENBIT:
 400                 if (arg)
 401                         client->flags |= I2C_M_TEN;
 402                 else
 403                         client->flags &= ~I2C_M_TEN;
 404                 return 0;
 405         case I2C_PEC:
 406                 if (arg)
 407                         client->flags |= I2C_CLIENT_PEC;
 408                 else
 409                         client->flags &= ~I2C_CLIENT_PEC;
 410                 return 0;
 411         case I2C_FUNCS:
 412                 funcs = i2c_get_functionality(client->adapter);
 413                 return put_user(funcs, (unsigned long __user *)arg);
 414
 415         case I2C_RDWR:
 416                 return i2cdev_ioctl_rdrw(client, arg);
 417
 418         case I2C_SMBUS:
 419                 return i2cdev_ioctl_smbus(client, arg);
 420
 421         case I2C_RETRIES:
 422                 client->adapter->retries = arg;
 423                 break;
 424         case I2C_TIMEOUT:
 425                 /* For historical reasons, user-space sets the timeout
 426                  * value in units of 10 ms.
 427                  */
 428                 client->adapter->timeout = msecs_to_jiffies(arg * 10);
 429                 break;
 430         default:
 431                 /* NOTE:  returning a fault code here could cause trouble
 432                  * in buggy userspace code.  Some old kernel bugs returned
 433                  * zero in this case, and userspace code might accidentally
 434                  * have depended on that bug.
 435                  */
 436                 return -ENOTTY;
 437         }
 438         return 0;
 439 }
 440
 441 static int i2cdev_open(struct inode *inode, struct file *file)
 442 {
 443         unsigned int minor = iminor(inode);
 444         struct i2c_client *client;
 445         struct i2c_adapter *adap;
 446         struct i2c_dev *i2c_dev;
 447
 448         i2c_dev = i2c_dev_get_by_minor(minor);
 449         if (!i2c_dev)
 450                 return -ENODEV;
 451
 452         adap = i2c_get_adapter(i2c_dev->adap->nr);
 453         if (!adap)
 454                 return -ENODEV;
 455
 456         /* This creates an anonymous i2c_client, which may later be
 457          * pointed to some address using I2C_SLAVE or I2C_SLAVE_FORCE.
 458          *
 459          * This client is ** NEVER REGISTERED ** with the driver model
 460          * or I2C core code!!  It just holds private copies of addressing
 461          * information and maybe a PEC flag.
 462          */
 463         client = kzalloc(sizeof(*client), GFP_KERNEL);
 464         if (!client) {
 465                 i2c_put_adapter(adap);
 466                 return -ENOMEM;
 467         }
 468         snprintf(client->name, I2C_NAME_SIZE, "i2c-dev %d", adap->nr);
 469         client->driver = &i2cdev_driver;
 470
 471         client->adapter = adap;
 472         file->private_data = client;
 473
 474         return 0;
 475 }
 476
 477 static int i2cdev_release(struct inode *inode, struct file *file)
 478 {
 479         struct i2c_client *client = file->private_data;
 480
 481         i2c_put_adapter(client->adapter);
 482         kfree(client);
 483         file->private_data = NULL;
 484
 485         return 0;
 486 }
 487
 488 static const struct file_operations i2cdev_fops = {
 489         .owner          = THIS_MODULE,
 490         .llseek         = no_llseek,
 491         .read           = i2cdev_read,
 492         .write          = i2cdev_write,
 493         .unlocked_ioctl = i2cdev_ioctl,
 494         .open           = i2cdev_open,
 495         .release        = i2cdev_release,
 496 };
 497
 498 /* ------------------------------------------------------------------------- */
 499
 500 /*
 501  * The legacy "i2cdev_driver" is used primarily to get notifications when
 502  * I2C adapters are added or removed, so that each one gets an i2c_dev
 503  * and is thus made available to userspace driver code.
 504  */
 505
 506 static struct class *i2c_dev_class;
 507
 508 static int i2cdev_attach_adapter(struct i2c_adapter *adap)
 509 {
 510         struct i2c_dev *i2c_dev;
 511         int res;
 512
 513         i2c_dev = get_free_i2c_dev(adap);
 514         if (IS_ERR(i2c_dev))
 515                 return PTR_ERR(i2c_dev);
 516
 517         /* register this i2c device with the driver core */
 518         i2c_dev->dev = device_create(i2c_dev_class, &adap->dev,
 519                                      MKDEV(I2C_MAJOR, adap->nr), NULL,
 520                                      "i2c-%d", adap->nr);
 521         if (IS_ERR(i2c_dev->dev)) {
 522                 res = PTR_ERR(i2c_dev->dev);
 523                 goto error;
 524         }
 525         res = device_create_file(i2c_dev->dev, &dev_attr_name);
 526         if (res)
 527                 goto error_destroy;
 528
 529         pr_debug("i2c-dev: adapter [%s] registered as minor %d\n",
 530                  adap->name, adap->nr);
 531         return 0;
 532 error_destroy:
 533         device_destroy(i2c_dev_class, MKDEV(I2C_MAJOR, adap->nr));
 534 error:
 535         return_i2c_dev(i2c_dev);
 536         return res;
 537 }
 538
 539 static int i2cdev_detach_adapter(struct i2c_adapter *adap)
 540 {
 541         struct i2c_dev *i2c_dev;
 542
 543         i2c_dev = i2c_dev_get_by_minor(adap->nr);
 544         if (!i2c_dev) /* attach_adapter must have failed */
 545                 return 0;
 546
 547         device_remove_file(i2c_dev->dev, &dev_attr_name);
 548         return_i2c_dev(i2c_dev);
 549         device_destroy(i2c_dev_class, MKDEV(I2C_MAJOR, adap->nr));
 550
 551         pr_debug("i2c-dev: adapter [%s] unregistered\n", adap->name);
 552         return 0;
 553 }
 554
 555 static struct i2c_driver i2cdev_driver = {
 556         .driver = {
 557                 .name   = "dev_driver",
 558         },
 559         .attach_adapter = i2cdev_attach_adapter,
 560         .detach_adapter = i2cdev_detach_adapter,
 561 };
 562
 563 /* ------------------------------------------------------------------------- */
 564
 565 /*
 566  * module load/unload record keeping
 567  */
 568
 569 static int __init i2c_dev_init(void)
 570 {
 571         int res;
 572
 573         printk(KERN_INFO "i2c /dev entries driver\n");
 574
 575         res = register_chrdev(I2C_MAJOR, "i2c", &i2cdev_fops);
 576         if (res)
 577                 goto out;
 578
 579         i2c_dev_class = class_create(THIS_MODULE, "i2c-dev");
 580         if (IS_ERR(i2c_dev_class)) {
 581                 res = PTR_ERR(i2c_dev_class);
 582                 goto out_unreg_chrdev;
 583         }
 584
 585         res = i2c_add_driver(&i2cdev_driver);
 586         if (res)
 587                 goto out_unreg_class;
 588
 589         return 0;
 590
 591 out_unreg_class:
 592         class_destroy(i2c_dev_class);
 593 out_unreg_chrdev:
 594         unregister_chrdev(I2C_MAJOR, "i2c");
 595 out:
 596         printk(KERN_ERR "%s: Driver Initialisation failed\n", __FILE__);
 597         return res;
 598 }
 599
 600 static void __exit i2c_dev_exit(void)
 601 {
 602         i2c_del_driver(&i2cdev_driver);
 603         class_destroy(i2c_dev_class);
 604         unregister_chrdev(I2C_MAJOR, "i2c");
 605 }
 606
 607 MODULE_AUTHOR("Frodo Looijaard <frodol@dds.nl> and "
 608                 "Simon G. Vogl <simon@tk.uni-linz.ac.at>");
 609 MODULE_DESCRIPTION("I2C /dev entries driver");
 610 MODULE_LICENSE("GPL");
 611
 612 module_init(i2c_dev_init);
 613 module_exit(i2c_dev_exit);