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/acpi.h>
  25 #include <linux/i2c.h>
  26 #include <linux/platform_data/at24.h>
  27
  28 /*
  29  * I2C EEPROMs from most vendors are inexpensive and mostly interchangeable.
  30  * Differences between different vendor product lines (like Atmel AT24C or
  31  * MicroChip 24LC, etc) won't much matter for typical read/write access.
  32  * There are also I2C RAM chips, likewise interchangeable. One example
  33  * would be the PCF8570, which acts like a 24c02 EEPROM (256 bytes).
  34  *
  35  * However, misconfiguration can lose data. "Set 16-bit memory address"
  36  * to a part with 8-bit addressing will overwrite data. Writing with too
  37  * big a page size also loses data. And it's not safe to assume that the
  38  * conventional addresses 0x50..0x57 only hold eeproms; a PCF8563 RTC
  39  * uses 0x51, for just one example.
  40  *
  41  * Accordingly, explicit board-specific configuration data should be used
  42  * in almost all cases. (One partial exception is an SMBus used to access
  43  * "SPD" data for DRAM sticks. Those only use 24c02 EEPROMs.)
  44  *
  45  * So this driver uses "new style" I2C driver binding, expecting to be
  46  * told what devices exist. That may be in arch/X/mach-Y/board-Z.c or
  47  * similar kernel-resident tables; or, configuration data coming from
  48  * a bootloader.
  49  *
  50  * Other than binding model, current differences from "eeprom" driver are
  51  * that this one handles write access and isn't restricted to 24c02 devices.
  52  * It also handles larger devices (32 kbit and up) with two-byte addresses,
  53  * which won't work on pure SMBus systems.
  54  */
  55
  56 struct at24_data {
  57         struct at24_platform_data chip;
  58         struct memory_accessor macc;
  59         int use_smbus;
  60         int use_smbus_write;
  61
  62         /*
  63          * Lock protects against activities from other Linux tasks,
  64          * but not from changes by other I2C masters.
  65          */
  66         struct mutex lock;
  67         struct bin_attribute bin;
  68
  69         u8 *writebuf;
  70         unsigned write_max;
  71         unsigned num_addresses;
  72
  73         /*
  74          * Some chips tie up multiple I2C addresses; dummy devices reserve
  75          * them for us, and we'll use them with SMBus calls.
  76          */
  77         struct i2c_client *client[];
  78 };
  79
  80 /*
  81  * This parameter is to help this driver avoid blocking other drivers out
  82  * of I2C for potentially troublesome amounts of time. With a 100 kHz I2C
  83  * clock, one 256 byte read takes about 1/43 second which is excessive;
  84  * but the 1/170 second it takes at 400 kHz may be quite reasonable; and
  85  * at 1 MHz (Fm+) a 1/430 second delay could easily be invisible.
  86  *
  87  * This value is forced to be a power of two so that writes align on pages.
  88  */
  89 static unsigned io_limit = 128;
  90 module_param(io_limit, uint, 0);
  91 MODULE_PARM_DESC(io_limit, "Maximum bytes per I/O (default 128)");
  92
  93 /*
  94  * Specs often allow 5 msec for a page write, sometimes 20 msec;
  95  * it's important to recover from write timeouts.
  96  */
  97 static unsigned write_timeout = 25;
  98 module_param(write_timeout, uint, 0);
  99 MODULE_PARM_DESC(write_timeout, "Time (in ms) to try writes (default 25)");
 100
 101 #define AT24_SIZE_BYTELEN 5
 102 #define AT24_SIZE_FLAGS 8
 103
 104 #define AT24_BITMASK(x) (BIT(x) - 1)
 105
 106 /* create non-zero magic value for given eeprom parameters */
 107 #define AT24_DEVICE_MAGIC(_len, _flags)                 \
 108         ((1 << AT24_SIZE_FLAGS | (_flags))              \
 109             << AT24_SIZE_BYTELEN | ilog2(_len))
 110
 111 static const struct i2c_device_id at24_ids[] = {
 112         /* needs 8 addresses as A0-A2 are ignored */
 113         { "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR) },
 114         /* old variants can't be handled with this generic entry! */
 115         { "24c01", AT24_DEVICE_MAGIC(1024 / 8, 0) },
 116         { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) },
 117         /* spd is a 24c02 in memory DIMMs */
 118         { "spd", AT24_DEVICE_MAGIC(2048 / 8,
 119                 AT24_FLAG_READONLY | AT24_FLAG_IRUGO) },
 120         { "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) },
 121         /* 24rf08 quirk is handled at i2c-core */
 122         { "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) },
 123         { "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) },
 124         { "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16) },
 125         { "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16) },
 126         { "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16) },
 127         { "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16) },
 128         { "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16) },
 129         { "24c1024", AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16) },
 130         { "at24", 0 },
 131         { /* END OF LIST */ }
 132 };
 133 MODULE_DEVICE_TABLE(i2c, at24_ids);
 134
 135 static const struct acpi_device_id at24_acpi_ids[] = {
 136         { "INT3499", AT24_DEVICE_MAGIC(8192 / 8, 0) },
 137         { }
 138 };
 139 MODULE_DEVICE_TABLE(acpi, at24_acpi_ids);
 140
 141 /*-------------------------------------------------------------------------*/
 142
 143 /*
 144  * This routine supports chips which consume multiple I2C addresses. It
 145  * computes the addressing information to be used for a given r/w request.
 146  * Assumes that sanity checks for offset happened at sysfs-layer.
 147  */
 148 static struct i2c_client *at24_translate_offset(struct at24_data *at24,
 149                 unsigned *offset)
 150 {
 151         unsigned i;
 152
 153         if (at24->chip.flags & AT24_FLAG_ADDR16) {
 154                 i = *offset >> 16;
 155                 *offset &= 0xffff;
 156         } else {
 157                 i = *offset >> 8;
 158                 *offset &= 0xff;
 159         }
 160
 161         return at24->client[i];
 162 }
 163
 164 static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
 165                 unsigned offset, size_t count)
 166 {
 167         struct i2c_msg msg[2];
 168         u8 msgbuf[2];
 169         struct i2c_client *client;
 170         unsigned long timeout, read_time;
 171         int status, i;
 172
 173         memset(msg, 0, sizeof(msg));
 174
 175         /*
 176          * REVISIT some multi-address chips don't rollover page reads to
 177          * the next slave address, so we may need to truncate the count.
 178          * Those chips might need another quirk flag.
 179          *
 180          * If the real hardware used four adjacent 24c02 chips and that
 181          * were misconfigured as one 24c08, that would be a similar effect:
 182          * one "eeprom" file not four, but larger reads would fail when
 183          * they crossed certain pages.
 184          */
 185
 186         /*
 187          * Slave address and byte offset derive from the offset. Always
 188          * set the byte address; on a multi-master board, another master
 189          * may have changed the chip's "current" address pointer.
 190          */
 191         client = at24_translate_offset(at24, &offset);
 192
 193         if (count > io_limit)
 194                 count = io_limit;
 195
 196         if (at24->use_smbus) {
 197                 /* Smaller eeproms can work given some SMBus extension calls */
 198                 if (count > I2C_SMBUS_BLOCK_MAX)
 199                         count = I2C_SMBUS_BLOCK_MAX;
 200         } else {
 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                 if (at24->use_smbus) {
 232                         status = i2c_smbus_read_i2c_block_data_or_emulated(client, offset,
 233                                                                            count, buf);
 234                 } else {
 235                         status = i2c_transfer(client->adapter, msg, 2);
 236                         if (status == 2)
 237                                 status = count;
 238                 }
 239                 dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
 240                                 count, offset, status, jiffies);
 241
 242                 if (status == count)
 243                         return count;
 244
 245                 /* REVISIT: at HZ=100, this is sloooow */
 246                 msleep(1);
 247         } while (time_before(read_time, timeout));
 248
 249         return -ETIMEDOUT;
 250 }
 251
 252 static ssize_t at24_read(struct at24_data *at24,
 253                 char *buf, loff_t off, size_t count)
 254 {
 255         ssize_t retval = 0;
 256
 257         if (unlikely(!count))
 258                 return count;
 259
 260         /*
 261          * Read data from chip, protecting against concurrent updates
 262          * from this host, but not from other I2C masters.
 263          */
 264         mutex_lock(&at24->lock);
 265
 266         while (count) {
 267                 ssize_t status;
 268
 269                 status = at24_eeprom_read(at24, buf, off, count);
 270                 if (status <= 0) {
 271                         if (retval == 0)
 272                                 retval = status;
 273                         break;
 274                 }
 275                 buf += status;
 276                 off += status;
 277                 count -= status;
 278                 retval += status;
 279         }
 280
 281         mutex_unlock(&at24->lock);
 282
 283         return retval;
 284 }
 285
 286 static ssize_t at24_bin_read(struct file *filp, struct kobject *kobj,
 287                 struct bin_attribute *attr,
 288                 char *buf, loff_t off, size_t count)
 289 {
 290         struct at24_data *at24;
 291
 292         at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
 293         return at24_read(at24, buf, off, count);
 294 }
 295
 296
 297 /*
 298  * Note that if the hardware write-protect pin is pulled high, the whole
 299  * chip is normally write protected. But there are plenty of product
 300  * variants here, including OTP fuses and partial chip protect.
 301  *
 302  * We only use page mode writes; the alternative is sloooow. This routine
 303  * writes at most one page.
 304  */
 305 static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
 306                 unsigned offset, size_t count)
 307 {
 308         struct i2c_client *client;
 309         struct i2c_msg msg;
 310         ssize_t status = 0;
 311         unsigned long timeout, write_time;
 312         unsigned next_page;
 313
 314         /* Get corresponding I2C address and adjust offset */
 315         client = at24_translate_offset(at24, &offset);
 316
 317         /* write_max is at most a page */
 318         if (count > at24->write_max)
 319                 count = at24->write_max;
 320
 321         /* Never roll over backwards, to the start of this page */
 322         next_page = roundup(offset + 1, at24->chip.page_size);
 323         if (offset + count > next_page)
 324                 count = next_page - offset;
 325
 326         /* If we'll use I2C calls for I/O, set up the message */
 327         if (!at24->use_smbus) {
 328                 int i = 0;
 329
 330                 msg.addr = client->addr;
 331                 msg.flags = 0;
 332
 333                 /* msg.buf is u8 and casts will mask the values */
 334                 msg.buf = at24->writebuf;
 335                 if (at24->chip.flags & AT24_FLAG_ADDR16)
 336                         msg.buf[i++] = offset >> 8;
 337
 338                 msg.buf[i++] = offset;
 339                 memcpy(&msg.buf[i], buf, count);
 340                 msg.len = i + count;
 341         }
 342
 343         /*
 344          * Writes fail if the previous one didn't complete yet. We may
 345          * loop a few times until this one succeeds, waiting at least
 346          * long enough for one entire page write to work.
 347          */
 348         timeout = jiffies + msecs_to_jiffies(write_timeout);
 349         do {
 350                 write_time = jiffies;
 351                 if (at24->use_smbus_write) {
 352                         switch (at24->use_smbus_write) {
 353                         case I2C_SMBUS_I2C_BLOCK_DATA:
 354                                 status = i2c_smbus_write_i2c_block_data(client,
 355                                                 offset, count, buf);
 356                                 break;
 357                         case I2C_SMBUS_BYTE_DATA:
 358                                 status = i2c_smbus_write_byte_data(client,
 359                                                 offset, buf[0]);
 360                                 break;
 361                         }
 362
 363                         if (status == 0)
 364                                 status = count;
 365                 } else {
 366                         status = i2c_transfer(client->adapter, &msg, 1);
 367                         if (status == 1)
 368                                 status = count;
 369                 }
 370                 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
 371                                 count, offset, status, jiffies);
 372
 373                 if (status == count)
 374                         return count;
 375
 376                 /* REVISIT: at HZ=100, this is sloooow */
 377                 msleep(1);
 378         } while (time_before(write_time, timeout));
 379
 380         return -ETIMEDOUT;
 381 }
 382
 383 static ssize_t at24_write(struct at24_data *at24, const char *buf, loff_t off,
 384                           size_t count)
 385 {
 386         ssize_t retval = 0;
 387
 388         if (unlikely(!count))
 389                 return count;
 390
 391         /*
 392          * Write data to chip, protecting against concurrent updates
 393          * from this host, but not from other I2C masters.
 394          */
 395         mutex_lock(&at24->lock);
 396
 397         while (count) {
 398                 ssize_t status;
 399
 400                 status = at24_eeprom_write(at24, buf, off, count);
 401                 if (status <= 0) {
 402                         if (retval == 0)
 403                                 retval = status;
 404                         break;
 405                 }
 406                 buf += status;
 407                 off += status;
 408                 count -= status;
 409                 retval += status;
 410         }
 411
 412         mutex_unlock(&at24->lock);
 413
 414         return retval;
 415 }
 416
 417 static ssize_t at24_bin_write(struct file *filp, struct kobject *kobj,
 418                 struct bin_attribute *attr,
 419                 char *buf, loff_t off, size_t count)
 420 {
 421         struct at24_data *at24;
 422
 423         at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
 424         return at24_write(at24, buf, off, count);
 425 }
 426
 427 /*-------------------------------------------------------------------------*/
 428
 429 /*
 430  * This lets other kernel code access the eeprom data. For example, it
 431  * might hold a board's Ethernet address, or board-specific calibration
 432  * data generated on the manufacturing floor.
 433  */
 434
 435 static ssize_t at24_macc_read(struct memory_accessor *macc, char *buf,
 436                          off_t offset, size_t count)
 437 {
 438         struct at24_data *at24 = container_of(macc, struct at24_data, macc);
 439
 440         return at24_read(at24, buf, offset, count);
 441 }
 442
 443 static ssize_t at24_macc_write(struct memory_accessor *macc, const 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_write(at24, buf, offset, count);
 449 }
 450
 451 /*-------------------------------------------------------------------------*/
 452
 453 #ifdef CONFIG_OF
 454 static void at24_get_ofdata(struct i2c_client *client,
 455                 struct at24_platform_data *chip)
 456 {
 457         const __be32 *val;
 458         struct device_node *node = client->dev.of_node;
 459
 460         if (node) {
 461                 if (of_get_property(node, "read-only", NULL))
 462                         chip->flags |= AT24_FLAG_READONLY;
 463                 val = of_get_property(node, "pagesize", NULL);
 464                 if (val)
 465                         chip->page_size = be32_to_cpup(val);
 466         }
 467 }
 468 #else
 469 static void at24_get_ofdata(struct i2c_client *client,
 470                 struct at24_platform_data *chip)
 471 { }
 472 #endif /* CONFIG_OF */
 473
 474 static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
 475 {
 476         struct at24_platform_data chip;
 477         kernel_ulong_t magic = 0;
 478         bool writable;
 479         int use_smbus = 0;
 480         int use_smbus_write = 0;
 481         struct at24_data *at24;
 482         int err;
 483         unsigned i, num_addresses;
 484
 485         if (client->dev.platform_data) {
 486                 chip = *(struct at24_platform_data *)client->dev.platform_data;
 487         } else {
 488                 if (id) {
 489                         magic = id->driver_data;
 490                 } else {
 491                         const struct acpi_device_id *aid;
 492
 493                         aid = acpi_match_device(at24_acpi_ids, &client->dev);
 494                         if (aid)
 495                                 magic = aid->driver_data;
 496                 }
 497                 if (!magic)
 498                         return -ENODEV;
 499
 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                 return -EINVAL;
 523         }
 524         if (!is_power_of_2(chip.page_size))
 525                 dev_warn(&client->dev,
 526                         "page_size looks suspicious (no power of 2)!\n");
 527
 528         /* Use I2C operations unless we're stuck with SMBus extensions. */
 529         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
 530                 if (chip.flags & AT24_FLAG_ADDR16)
 531                         return -EPFNOSUPPORT;
 532
 533                 if (i2c_check_functionality(client->adapter,
 534                                 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
 535                         use_smbus = I2C_SMBUS_I2C_BLOCK_DATA;
 536                 } else if (i2c_check_functionality(client->adapter,
 537                                 I2C_FUNC_SMBUS_READ_WORD_DATA)) {
 538                         use_smbus = I2C_SMBUS_WORD_DATA;
 539                 } else if (i2c_check_functionality(client->adapter,
 540                                 I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
 541                         use_smbus = I2C_SMBUS_BYTE_DATA;
 542                 } else {
 543                         return -EPFNOSUPPORT;
 544                 }
 545         }
 546
 547         /* Use I2C operations unless we're stuck with SMBus extensions. */
 548         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
 549                 if (i2c_check_functionality(client->adapter,
 550                                 I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
 551                         use_smbus_write = I2C_SMBUS_I2C_BLOCK_DATA;
 552                 } else if (i2c_check_functionality(client->adapter,
 553                                 I2C_FUNC_SMBUS_WRITE_BYTE_DATA)) {
 554                         use_smbus_write = I2C_SMBUS_BYTE_DATA;
 555                         chip.page_size = 1;
 556                 }
 557         }
 558
 559         if (chip.flags & AT24_FLAG_TAKE8ADDR)
 560                 num_addresses = 8;
 561         else
 562                 num_addresses = DIV_ROUND_UP(chip.byte_len,
 563                         (chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
 564
 565         at24 = devm_kzalloc(&client->dev, sizeof(struct at24_data) +
 566                 num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
 567         if (!at24)
 568                 return -ENOMEM;
 569
 570         mutex_init(&at24->lock);
 571         at24->use_smbus = use_smbus;
 572         at24->use_smbus_write = use_smbus_write;
 573         at24->chip = chip;
 574         at24->num_addresses = num_addresses;
 575
 576         /*
 577          * Export the EEPROM bytes through sysfs, since that's convenient.
 578          * By default, only root should see the data (maybe passwords etc)
 579          */
 580         sysfs_bin_attr_init(&at24->bin);
 581         at24->bin.attr.name = "eeprom";
 582         at24->bin.attr.mode = chip.flags & AT24_FLAG_IRUGO ? S_IRUGO : S_IRUSR;
 583         at24->bin.read = at24_bin_read;
 584         at24->bin.size = chip.byte_len;
 585
 586         at24->macc.read = at24_macc_read;
 587
 588         writable = !(chip.flags & AT24_FLAG_READONLY);
 589         if (writable) {
 590                 if (!use_smbus || use_smbus_write) {
 591
 592                         unsigned write_max = chip.page_size;
 593
 594                         at24->macc.write = at24_macc_write;
 595
 596                         at24->bin.write = at24_bin_write;
 597                         at24->bin.attr.mode |= S_IWUSR;
 598
 599                         if (write_max > io_limit)
 600                                 write_max = io_limit;
 601                         if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
 602                                 write_max = I2C_SMBUS_BLOCK_MAX;
 603                         at24->write_max = write_max;
 604
 605                         /* buffer (data + address at the beginning) */
 606                         at24->writebuf = devm_kzalloc(&client->dev,
 607                                 write_max + 2, GFP_KERNEL);
 608                         if (!at24->writebuf)
 609                                 return -ENOMEM;
 610                 } else {
 611                         dev_warn(&client->dev,
 612                                 "cannot write due to controller restrictions.");
 613                 }
 614         }
 615
 616         at24->client[0] = client;
 617
 618         /* use dummy devices for multiple-address chips */
 619         for (i = 1; i < num_addresses; i++) {
 620                 at24->client[i] = i2c_new_dummy(client->adapter,
 621                                         client->addr + i);
 622                 if (!at24->client[i]) {
 623                         dev_err(&client->dev, "address 0x%02x unavailable\n",
 624                                         client->addr + i);
 625                         err = -EADDRINUSE;
 626                         goto err_clients;
 627                 }
 628         }
 629
 630         err = sysfs_create_bin_file(&client->dev.kobj, &at24->bin);
 631         if (err)
 632                 goto err_clients;
 633
 634         i2c_set_clientdata(client, at24);
 635
 636         dev_info(&client->dev, "%zu byte %s EEPROM, %s, %u bytes/write\n",
 637                 at24->bin.size, client->name,
 638                 writable ? "writable" : "read-only", at24->write_max);
 639         if (use_smbus == I2C_SMBUS_WORD_DATA ||
 640             use_smbus == I2C_SMBUS_BYTE_DATA) {
 641                 dev_notice(&client->dev, "Falling back to %s reads, "
 642                            "performance will suffer\n", use_smbus ==
 643                            I2C_SMBUS_WORD_DATA ? "word" : "byte");
 644         }
 645
 646         /* export data to kernel code */
 647         if (chip.setup)
 648                 chip.setup(&at24->macc, chip.context);
 649
 650         return 0;
 651
 652 err_clients:
 653         for (i = 1; i < num_addresses; i++)
 654                 if (at24->client[i])
 655                         i2c_unregister_device(at24->client[i]);
 656
 657         return err;
 658 }
 659
 660 static int at24_remove(struct i2c_client *client)
 661 {
 662         struct at24_data *at24;
 663         int i;
 664
 665         at24 = i2c_get_clientdata(client);
 666         sysfs_remove_bin_file(&client->dev.kobj, &at24->bin);
 667
 668         for (i = 1; i < at24->num_addresses; i++)
 669                 i2c_unregister_device(at24->client[i]);
 670
 671         return 0;
 672 }
 673
 674 /*-------------------------------------------------------------------------*/
 675
 676 static struct i2c_driver at24_driver = {
 677         .driver = {
 678                 .name = "at24",
 679                 .acpi_match_table = ACPI_PTR(at24_acpi_ids),
 680         },
 681         .probe = at24_probe,
 682         .remove = at24_remove,
 683         .id_table = at24_ids,
 684 };
 685
 686 static int __init at24_init(void)
 687 {
 688         if (!io_limit) {
 689                 pr_err("at24: io_limit must not be 0!\n");
 690                 return -EINVAL;
 691         }
 692
 693         io_limit = rounddown_pow_of_two(io_limit);
 694         return i2c_add_driver(&at24_driver);
 695 }
 696 module_init(at24_init);
 697
 698 static void __exit at24_exit(void)
 699 {
 700         i2c_del_driver(&at24_driver);
 701 }
 702 module_exit(at24_exit);
 703
 704 MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
 705 MODULE_AUTHOR("David Brownell and Wolfram Sang");
 706 MODULE_LICENSE("GPL");