drivers/misc/eeprom/at24.c

   1 /*
   2  * at24.c - handle most I2C EEPROMs
   3  *
   4  * Copyright (C) 2005-2007 David Brownell
   5  * Copyright (C) 2008 Wolfram Sang, Pengutronix
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  */
  12 #include <linux/kernel.h>
  13 #include <linux/init.h>
  14 #include <linux/module.h>
  15 #include <linux/slab.h>
  16 #include <linux/delay.h>
  17 #include <linux/mutex.h>
  18 #include <linux/sysfs.h>
  19 #include <linux/mod_devicetable.h>
  20 #include <linux/log2.h>
  21 #include <linux/bitops.h>
  22 #include <linux/jiffies.h>
  23 #include <linux/of.h>
  24 #include <linux/i2c.h>
  25 #include <linux/i2c/at24.h>
  26
  27 /*
  28  * I2C EEPROMs from most vendors are inexpensive and mostly interchangeable.
  29  * Differences between different vendor product lines (like Atmel AT24C or
  30  * MicroChip 24LC, etc) won't much matter for typical read/write access.
  31  * There are also I2C RAM chips, likewise interchangeable. One example
  32  * would be the PCF8570, which acts like a 24c02 EEPROM (256 bytes).
  33  *
  34  * However, misconfiguration can lose data. "Set 16-bit memory address"
  35  * to a part with 8-bit addressing will overwrite data. Writing with too
  36  * big a page size also loses data. And it's not safe to assume that the
  37  * conventional addresses 0x50..0x57 only hold eeproms; a PCF8563 RTC
  38  * uses 0x51, for just one example.
  39  *
  40  * Accordingly, explicit board-specific configuration data should be used
  41  * in almost all cases. (One partial exception is an SMBus used to access
  42  * "SPD" data for DRAM sticks. Those only use 24c02 EEPROMs.)
  43  *
  44  * So this driver uses "new style" I2C driver binding, expecting to be
  45  * told what devices exist. That may be in arch/X/mach-Y/board-Z.c or
  46  * similar kernel-resident tables; or, configuration data coming from
  47  * a bootloader.
  48  *
  49  * Other than binding model, current differences from "eeprom" driver are
  50  * that this one handles write access and isn't restricted to 24c02 devices.
  51  * It also handles larger devices (32 kbit and up) with two-byte addresses,
  52  * which won't work on pure SMBus systems.
  53  */
  54
  55 struct at24_data {
  56         struct at24_platform_data chip;
  57         struct memory_accessor macc;
  58         int use_smbus;
  59
  60         /*
  61          * Lock protects against activities from other Linux tasks,
  62          * but not from changes by other I2C masters.
  63          */
  64         struct mutex lock;
  65         struct bin_attribute bin;
  66
  67         u8 *writebuf;
  68         unsigned write_max;
  69         unsigned num_addresses;
  70
  71         /*
  72          * Some chips tie up multiple I2C addresses; dummy devices reserve
  73          * them for us, and we'll use them with SMBus calls.
  74          */
  75         struct i2c_client *client[];
  76 };
  77
  78 /*
  79  * This parameter is to help this driver avoid blocking other drivers out
  80  * of I2C for potentially troublesome amounts of time. With a 100 kHz I2C
  81  * clock, one 256 byte read takes about 1/43 second which is excessive;
  82  * but the 1/170 second it takes at 400 kHz may be quite reasonable; and
  83  * at 1 MHz (Fm+) a 1/430 second delay could easily be invisible.
  84  *
  85  * This value is forced to be a power of two so that writes align on pages.
  86  */
  87 static unsigned io_limit = 128;
  88 module_param(io_limit, uint, 0);
  89 MODULE_PARM_DESC(io_limit, "Maximum bytes per I/O (default 128)");
  90
  91 /*
  92  * Specs often allow 5 msec for a page write, sometimes 20 msec;
  93  * it's important to recover from write timeouts.
  94  */
  95 static unsigned write_timeout = 25;
  96 module_param(write_timeout, uint, 0);
  97 MODULE_PARM_DESC(write_timeout, "Time (in ms) to try writes (default 25)");
  98
  99 #define AT24_SIZE_BYTELEN 5
 100 #define AT24_SIZE_FLAGS 8
 101
 102 #define AT24_BITMASK(x) (BIT(x) - 1)
 103
 104 /* create non-zero magic value for given eeprom parameters */
 105 #define AT24_DEVICE_MAGIC(_len, _flags)                 \
 106         ((1 << AT24_SIZE_FLAGS | (_flags))              \
 107             << AT24_SIZE_BYTELEN | ilog2(_len))
 108
 109 static const struct i2c_device_id at24_ids[] = {
 110         /* needs 8 addresses as A0-A2 are ignored */
 111         { "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR) },
 112         /* old variants can't be handled with this generic entry! */
 113         { "24c01", AT24_DEVICE_MAGIC(1024 / 8, 0) },
 114         { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) },
 115         /* spd is a 24c02 in memory DIMMs */
 116         { "spd", AT24_DEVICE_MAGIC(2048 / 8,
 117                 AT24_FLAG_READONLY | AT24_FLAG_IRUGO) },
 118         { "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) },
 119         /* 24rf08 quirk is handled at i2c-core */
 120         { "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) },
 121         { "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) },
 122         { "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16) },
 123         { "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16) },
 124         { "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16) },
 125         { "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16) },
 126         { "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16) },
 127         { "24c1024", AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16) },
 128         { "at24", 0 },
 129         { /* END OF LIST */ }
 130 };
 131 MODULE_DEVICE_TABLE(i2c, at24_ids);
 132
 133 /*-------------------------------------------------------------------------*/
 134
 135 /*
 136  * This routine supports chips which consume multiple I2C addresses. It
 137  * computes the addressing information to be used for a given r/w request.
 138  * Assumes that sanity checks for offset happened at sysfs-layer.
 139  */
 140 static struct i2c_client *at24_translate_offset(struct at24_data *at24,
 141                 unsigned *offset)
 142 {
 143         unsigned i;
 144
 145         if (at24->chip.flags & AT24_FLAG_ADDR16) {
 146                 i = *offset >> 16;
 147                 *offset &= 0xffff;
 148         } else {
 149                 i = *offset >> 8;
 150                 *offset &= 0xff;
 151         }
 152
 153         return at24->client[i];
 154 }
 155
 156 static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
 157                 unsigned offset, size_t count)
 158 {
 159         struct i2c_msg msg[2];
 160         u8 msgbuf[2];
 161         struct i2c_client *client;
 162         unsigned long timeout, read_time;
 163         int status, i;
 164
 165         memset(msg, 0, sizeof(msg));
 166
 167         /*
 168          * REVISIT some multi-address chips don't rollover page reads to
 169          * the next slave address, so we may need to truncate the count.
 170          * Those chips might need another quirk flag.
 171          *
 172          * If the real hardware used four adjacent 24c02 chips and that
 173          * were misconfigured as one 24c08, that would be a similar effect:
 174          * one "eeprom" file not four, but larger reads would fail when
 175          * they crossed certain pages.
 176          */
 177
 178         /*
 179          * Slave address and byte offset derive from the offset. Always
 180          * set the byte address; on a multi-master board, another master
 181          * may have changed the chip's "current" address pointer.
 182          */
 183         client = at24_translate_offset(at24, &offset);
 184
 185         if (count > io_limit)
 186                 count = io_limit;
 187
 188         switch (at24->use_smbus) {
 189         case I2C_SMBUS_I2C_BLOCK_DATA:
 190                 /* Smaller eeproms can work given some SMBus extension calls */
 191                 if (count > I2C_SMBUS_BLOCK_MAX)
 192                         count = I2C_SMBUS_BLOCK_MAX;
 193                 break;
 194         case I2C_SMBUS_WORD_DATA:
 195                 count = 2;
 196                 break;
 197         case I2C_SMBUS_BYTE_DATA:
 198                 count = 1;
 199                 break;
 200         default:
 201                 /*
 202                  * When we have a better choice than SMBus calls, use a
 203                  * combined I2C message. Write address; then read up to
 204                  * io_limit data bytes. Note that read page rollover helps us
 205                  * here (unlike writes). msgbuf is u8 and will cast to our
 206                  * needs.
 207                  */
 208                 i = 0;
 209                 if (at24->chip.flags & AT24_FLAG_ADDR16)
 210                         msgbuf[i++] = offset >> 8;
 211                 msgbuf[i++] = offset;
 212
 213                 msg[0].addr = client->addr;
 214                 msg[0].buf = msgbuf;
 215                 msg[0].len = i;
 216
 217                 msg[1].addr = client->addr;
 218                 msg[1].flags = I2C_M_RD;
 219                 msg[1].buf = buf;
 220                 msg[1].len = count;
 221         }
 222
 223         /*
 224          * Reads fail if the previous write didn't complete yet. We may
 225          * loop a few times until this one succeeds, waiting at least
 226          * long enough for one entire page write to work.
 227          */
 228         timeout = jiffies + msecs_to_jiffies(write_timeout);
 229         do {
 230                 read_time = jiffies;
 231                 switch (at24->use_smbus) {
 232                 case I2C_SMBUS_I2C_BLOCK_DATA:
 233                         status = i2c_smbus_read_i2c_block_data(client, offset,
 234                                         count, buf);
 235                         break;
 236                 case I2C_SMBUS_WORD_DATA:
 237                         status = i2c_smbus_read_word_data(client, offset);
 238                         if (status >= 0) {
 239                                 buf[0] = status & 0xff;
 240                                 buf[1] = status >> 8;
 241                                 status = count;
 242                         }
 243                         break;
 244                 case I2C_SMBUS_BYTE_DATA:
 245                         status = i2c_smbus_read_byte_data(client, offset);
 246                         if (status >= 0) {
 247                                 buf[0] = status;
 248                                 status = count;
 249                         }
 250                         break;
 251                 default:
 252                         status = i2c_transfer(client->adapter, msg, 2);
 253                         if (status == 2)
 254                                 status = count;
 255                 }
 256                 dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
 257                                 count, offset, status, jiffies);
 258
 259                 if (status == count)
 260                         return count;
 261
 262                 /* REVISIT: at HZ=100, this is sloooow */
 263                 msleep(1);
 264         } while (time_before(read_time, timeout));
 265
 266         return -ETIMEDOUT;
 267 }
 268
 269 static ssize_t at24_read(struct at24_data *at24,
 270                 char *buf, loff_t off, size_t count)
 271 {
 272         ssize_t retval = 0;
 273
 274         if (unlikely(!count))
 275                 return count;
 276
 277         /*
 278          * Read data from chip, protecting against concurrent updates
 279          * from this host, but not from other I2C masters.
 280          */
 281         mutex_lock(&at24->lock);
 282
 283         while (count) {
 284                 ssize_t status;
 285
 286                 status = at24_eeprom_read(at24, buf, off, count);
 287                 if (status <= 0) {
 288                         if (retval == 0)
 289                                 retval = status;
 290                         break;
 291                 }
 292                 buf += status;
 293                 off += status;
 294                 count -= status;
 295                 retval += status;
 296         }
 297
 298         mutex_unlock(&at24->lock);
 299
 300         return retval;
 301 }
 302
 303 static ssize_t at24_bin_read(struct file *filp, struct kobject *kobj,
 304                 struct bin_attribute *attr,
 305                 char *buf, loff_t off, size_t count)
 306 {
 307         struct at24_data *at24;
 308
 309         at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
 310         return at24_read(at24, buf, off, count);
 311 }
 312
 313
 314 /*
 315  * Note that if the hardware write-protect pin is pulled high, the whole
 316  * chip is normally write protected. But there are plenty of product
 317  * variants here, including OTP fuses and partial chip protect.
 318  *
 319  * We only use page mode writes; the alternative is sloooow. This routine
 320  * writes at most one page.
 321  */
 322 static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
 323                 unsigned offset, size_t count)
 324 {
 325         struct i2c_client *client;
 326         struct i2c_msg msg;
 327         ssize_t status;
 328         unsigned long timeout, write_time;
 329         unsigned next_page;
 330
 331         /* Get corresponding I2C address and adjust offset */
 332         client = at24_translate_offset(at24, &offset);
 333
 334         /* write_max is at most a page */
 335         if (count > at24->write_max)
 336                 count = at24->write_max;
 337
 338         /* Never roll over backwards, to the start of this page */
 339         next_page = roundup(offset + 1, at24->chip.page_size);
 340         if (offset + count > next_page)
 341                 count = next_page - offset;
 342
 343         /* If we'll use I2C calls for I/O, set up the message */
 344         if (!at24->use_smbus) {
 345                 int i = 0;
 346
 347                 msg.addr = client->addr;
 348                 msg.flags = 0;
 349
 350                 /* msg.buf is u8 and casts will mask the values */
 351                 msg.buf = at24->writebuf;
 352                 if (at24->chip.flags & AT24_FLAG_ADDR16)
 353                         msg.buf[i++] = offset >> 8;
 354
 355                 msg.buf[i++] = offset;
 356                 memcpy(&msg.buf[i], buf, count);
 357                 msg.len = i + count;
 358         }
 359
 360         /*
 361          * Writes fail if the previous one didn't complete yet. We may
 362          * loop a few times until this one succeeds, waiting at least
 363          * long enough for one entire page write to work.
 364          */
 365         timeout = jiffies + msecs_to_jiffies(write_timeout);
 366         do {
 367                 write_time = jiffies;
 368                 if (at24->use_smbus) {
 369                         status = i2c_smbus_write_i2c_block_data(client,
 370                                         offset, count, buf);
 371                         if (status == 0)
 372                                 status = count;
 373                 } else {
 374                         status = i2c_transfer(client->adapter, &msg, 1);
 375                         if (status == 1)
 376                                 status = count;
 377                 }
 378                 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
 379                                 count, offset, status, jiffies);
 380
 381                 if (status == count)
 382                         return count;
 383
 384                 /* REVISIT: at HZ=100, this is sloooow */
 385                 msleep(1);
 386         } while (time_before(write_time, timeout));
 387
 388         return -ETIMEDOUT;
 389 }
 390
 391 static ssize_t at24_write(struct at24_data *at24, const char *buf, loff_t off,
 392                           size_t count)
 393 {
 394         ssize_t retval = 0;
 395
 396         if (unlikely(!count))
 397                 return count;
 398
 399         /*
 400          * Write data to chip, protecting against concurrent updates
 401          * from this host, but not from other I2C masters.
 402          */
 403         mutex_lock(&at24->lock);
 404
 405         while (count) {
 406                 ssize_t status;
 407
 408                 status = at24_eeprom_write(at24, buf, off, count);
 409                 if (status <= 0) {
 410                         if (retval == 0)
 411                                 retval = status;
 412                         break;
 413                 }
 414                 buf += status;
 415                 off += status;
 416                 count -= status;
 417                 retval += status;
 418         }
 419
 420         mutex_unlock(&at24->lock);
 421
 422         return retval;
 423 }
 424
 425 static ssize_t at24_bin_write(struct file *filp, struct kobject *kobj,
 426                 struct bin_attribute *attr,
 427                 char *buf, loff_t off, size_t count)
 428 {
 429         struct at24_data *at24;
 430
 431         at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
 432         return at24_write(at24, buf, off, count);
 433 }
 434
 435 /*-------------------------------------------------------------------------*/
 436
 437 /*
 438  * This lets other kernel code access the eeprom data. For example, it
 439  * might hold a board's Ethernet address, or board-specific calibration
 440  * data generated on the manufacturing floor.
 441  */
 442
 443 static ssize_t at24_macc_read(struct memory_accessor *macc, char *buf,
 444                          off_t offset, size_t count)
 445 {
 446         struct at24_data *at24 = container_of(macc, struct at24_data, macc);
 447
 448         return at24_read(at24, buf, offset, count);
 449 }
 450
 451 static ssize_t at24_macc_write(struct memory_accessor *macc, const char *buf,
 452                           off_t offset, size_t count)
 453 {
 454         struct at24_data *at24 = container_of(macc, struct at24_data, macc);
 455
 456         return at24_write(at24, buf, offset, count);
 457 }
 458
 459 /*-------------------------------------------------------------------------*/
 460
 461 #ifdef CONFIG_OF
 462 static void at24_get_ofdata(struct i2c_client *client,
 463                 struct at24_platform_data *chip)
 464 {
 465         const __be32 *val;
 466         struct device_node *node = client->dev.of_node;
 467
 468         if (node) {
 469                 if (of_get_property(node, "read-only", NULL))
 470                         chip->flags |= AT24_FLAG_READONLY;
 471                 val = of_get_property(node, "pagesize", NULL);
 472                 if (val)
 473                         chip->page_size = be32_to_cpup(val);
 474         }
 475 }
 476 #else
 477 static void at24_get_ofdata(struct i2c_client *client,
 478                 struct at24_platform_data *chip)
 479 { }
 480 #endif /* CONFIG_OF */
 481
 482 static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
 483 {
 484         struct at24_platform_data chip;
 485         bool writable;
 486         int use_smbus = 0;
 487         struct at24_data *at24;
 488         int err;
 489         unsigned i, num_addresses;
 490         kernel_ulong_t magic;
 491
 492         if (client->dev.platform_data) {
 493                 chip = *(struct at24_platform_data *)client->dev.platform_data;
 494         } else {
 495                 if (!id->driver_data) {
 496                         err = -ENODEV;
 497                         goto err_out;
 498                 }
 499                 magic = id->driver_data;
 500                 chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
 501                 magic >>= AT24_SIZE_BYTELEN;
 502                 chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
 503                 /*
 504                  * This is slow, but we can't know all eeproms, so we better
 505                  * play safe. Specifying custom eeprom-types via platform_data
 506                  * is recommended anyhow.
 507                  */
 508                 chip.page_size = 1;
 509
 510                 /* update chipdata if OF is present */
 511                 at24_get_ofdata(client, &chip);
 512
 513                 chip.setup = NULL;
 514                 chip.context = NULL;
 515         }
 516
 517         if (!is_power_of_2(chip.byte_len))
 518                 dev_warn(&client->dev,
 519                         "byte_len looks suspicious (no power of 2)!\n");
 520         if (!chip.page_size) {
 521                 dev_err(&client->dev, "page_size must not be 0!\n");
 522                 err = -EINVAL;
 523                 goto err_out;
 524         }
 525         if (!is_power_of_2(chip.page_size))
 526                 dev_warn(&client->dev,
 527                         "page_size looks suspicious (no power of 2)!\n");
 528
 529         /* Use I2C operations unless we're stuck with SMBus extensions. */
 530         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
 531                 if (chip.flags & AT24_FLAG_ADDR16) {
 532                         err = -EPFNOSUPPORT;
 533                         goto err_out;
 534                 }
 535                 if (i2c_check_functionality(client->adapter,
 536                                 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
 537                         use_smbus = I2C_SMBUS_I2C_BLOCK_DATA;
 538                 } else if (i2c_check_functionality(client->adapter,
 539                                 I2C_FUNC_SMBUS_READ_WORD_DATA)) {
 540                         use_smbus = I2C_SMBUS_WORD_DATA;
 541                 } else if (i2c_check_functionality(client->adapter,
 542                                 I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
 543                         use_smbus = I2C_SMBUS_BYTE_DATA;
 544                 } else {
 545                         err = -EPFNOSUPPORT;
 546                         goto err_out;
 547                 }
 548         }
 549
 550         if (chip.flags & AT24_FLAG_TAKE8ADDR)
 551                 num_addresses = 8;
 552         else
 553                 num_addresses = DIV_ROUND_UP(chip.byte_len,
 554                         (chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
 555
 556         at24 = kzalloc(sizeof(struct at24_data) +
 557                 num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
 558         if (!at24) {
 559                 err = -ENOMEM;
 560                 goto err_out;
 561         }
 562
 563         mutex_init(&at24->lock);
 564         at24->use_smbus = use_smbus;
 565         at24->chip = chip;
 566         at24->num_addresses = num_addresses;
 567
 568         /*
 569          * Export the EEPROM bytes through sysfs, since that's convenient.
 570          * By default, only root should see the data (maybe passwords etc)
 571          */
 572         sysfs_bin_attr_init(&at24->bin);
 573         at24->bin.attr.name = "eeprom";
 574         at24->bin.attr.mode = chip.flags & AT24_FLAG_IRUGO ? S_IRUGO : S_IRUSR;
 575         at24->bin.read = at24_bin_read;
 576         at24->bin.size = chip.byte_len;
 577
 578         at24->macc.read = at24_macc_read;
 579
 580         writable = !(chip.flags & AT24_FLAG_READONLY);
 581         if (writable) {
 582                 if (!use_smbus || i2c_check_functionality(client->adapter,
 583                                 I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
 584
 585                         unsigned write_max = chip.page_size;
 586
 587                         at24->macc.write = at24_macc_write;
 588
 589                         at24->bin.write = at24_bin_write;
 590                         at24->bin.attr.mode |= S_IWUSR;
 591
 592                         if (write_max > io_limit)
 593                                 write_max = io_limit;
 594                         if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
 595                                 write_max = I2C_SMBUS_BLOCK_MAX;
 596                         at24->write_max = write_max;
 597
 598                         /* buffer (data + address at the beginning) */
 599                         at24->writebuf = kmalloc(write_max + 2, GFP_KERNEL);
 600                         if (!at24->writebuf) {
 601                                 err = -ENOMEM;
 602                                 goto err_struct;
 603                         }
 604                 } else {
 605                         dev_warn(&client->dev,
 606                                 "cannot write due to controller restrictions.");
 607                 }
 608         }
 609
 610         at24->client[0] = client;
 611
 612         /* use dummy devices for multiple-address chips */
 613         for (i = 1; i < num_addresses; i++) {
 614                 at24->client[i] = i2c_new_dummy(client->adapter,
 615                                         client->addr + i);
 616                 if (!at24->client[i]) {
 617                         dev_err(&client->dev, "address 0x%02x unavailable\n",
 618                                         client->addr + i);
 619                         err = -EADDRINUSE;
 620                         goto err_clients;
 621                 }
 622         }
 623
 624         err = sysfs_create_bin_file(&client->dev.kobj, &at24->bin);
 625         if (err)
 626                 goto err_clients;
 627
 628         i2c_set_clientdata(client, at24);
 629
 630         dev_info(&client->dev, "%zu byte %s EEPROM, %s, %u bytes/write\n",
 631                 at24->bin.size, client->name,
 632                 writable ? "writable" : "read-only", at24->write_max);
 633         if (use_smbus == I2C_SMBUS_WORD_DATA ||
 634             use_smbus == I2C_SMBUS_BYTE_DATA) {
 635                 dev_notice(&client->dev, "Falling back to %s reads, "
 636                            "performance will suffer\n", use_smbus ==
 637                            I2C_SMBUS_WORD_DATA ? "word" : "byte");
 638         }
 639
 640         /* export data to kernel code */
 641         if (chip.setup)
 642                 chip.setup(&at24->macc, chip.context);
 643
 644         return 0;
 645
 646 err_clients:
 647         for (i = 1; i < num_addresses; i++)
 648                 if (at24->client[i])
 649                         i2c_unregister_device(at24->client[i]);
 650
 651         kfree(at24->writebuf);
 652 err_struct:
 653         kfree(at24);
 654 err_out:
 655         dev_dbg(&client->dev, "probe error %d\n", err);
 656         return err;
 657 }
 658
 659 static int __devexit at24_remove(struct i2c_client *client)
 660 {
 661         struct at24_data *at24;
 662         int i;
 663
 664         at24 = i2c_get_clientdata(client);
 665         sysfs_remove_bin_file(&client->dev.kobj, &at24->bin);
 666
 667         for (i = 1; i < at24->num_addresses; i++)
 668                 i2c_unregister_device(at24->client[i]);
 669
 670         kfree(at24->writebuf);
 671         kfree(at24);
 672         return 0;
 673 }
 674
 675 /*-------------------------------------------------------------------------*/
 676
 677 static struct i2c_driver at24_driver = {
 678         .driver = {
 679                 .name = "at24",
 680                 .owner = THIS_MODULE,
 681         },
 682         .probe = at24_probe,
 683         .remove = __devexit_p(at24_remove),
 684         .id_table = at24_ids,
 685 };
 686
 687 static int __init at24_init(void)
 688 {
 689         if (!io_limit) {
 690                 pr_err("at24: io_limit must not be 0!\n");
 691                 return -EINVAL;
 692         }
 693
 694         io_limit = rounddown_pow_of_two(io_limit);
 695         return i2c_add_driver(&at24_driver);
 696 }
 697 module_init(at24_init);
 698
 699 static void __exit at24_exit(void)
 700 {
 701         i2c_del_driver(&at24_driver);
 702 }
 703 module_exit(at24_exit);
 704
 705 MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
 706 MODULE_AUTHOR("David Brownell and Wolfram Sang");
 707 MODULE_LICENSE("GPL");