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/platform_data/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         int use_smbus_write;
  60
  61         /*
  62          * Lock protects against activities from other Linux tasks,
  63          * but not from changes by other I2C masters.
  64          */
  65         struct mutex lock;
  66         struct bin_attribute bin;
  67
  68         u8 *writebuf;
  69         unsigned write_max;
  70         unsigned num_addresses;
  71
  72         /*
  73          * Some chips tie up multiple I2C addresses; dummy devices reserve
  74          * them for us, and we'll use them with SMBus calls.
  75          */
  76         struct i2c_client *client[];
  77 };
  78
  79 /*
  80  * This parameter is to help this driver avoid blocking other drivers out
  81  * of I2C for potentially troublesome amounts of time. With a 100 kHz I2C
  82  * clock, one 256 byte read takes about 1/43 second which is excessive;
  83  * but the 1/170 second it takes at 400 kHz may be quite reasonable; and
  84  * at 1 MHz (Fm+) a 1/430 second delay could easily be invisible.
  85  *
  86  * This value is forced to be a power of two so that writes align on pages.
  87  */
  88 static unsigned io_limit = 128;
  89 module_param(io_limit, uint, 0);
  90 MODULE_PARM_DESC(io_limit, "Maximum bytes per I/O (default 128)");
  91
  92 /*
  93  * Specs often allow 5 msec for a page write, sometimes 20 msec;
  94  * it's important to recover from write timeouts.
  95  */
  96 static unsigned write_timeout = 25;
  97 module_param(write_timeout, uint, 0);
  98 MODULE_PARM_DESC(write_timeout, "Time (in ms) to try writes (default 25)");
  99
 100 #define AT24_SIZE_BYTELEN 5
 101 #define AT24_SIZE_FLAGS 8
 102
 103 #define AT24_BITMASK(x) (BIT(x) - 1)
 104
 105 /* create non-zero magic value for given eeprom parameters */
 106 #define AT24_DEVICE_MAGIC(_len, _flags)                 \
 107         ((1 << AT24_SIZE_FLAGS | (_flags))              \
 108             << AT24_SIZE_BYTELEN | ilog2(_len))
 109
 110 static const struct i2c_device_id at24_ids[] = {
 111         /* needs 8 addresses as A0-A2 are ignored */
 112         { "24c00", AT24_DEVICE_MAGIC(128 / 8, AT24_FLAG_TAKE8ADDR) },
 113         /* old variants can't be handled with this generic entry! */
 114         { "24c01", AT24_DEVICE_MAGIC(1024 / 8, 0) },
 115         { "24c02", AT24_DEVICE_MAGIC(2048 / 8, 0) },
 116         /* spd is a 24c02 in memory DIMMs */
 117         { "spd", AT24_DEVICE_MAGIC(2048 / 8,
 118                 AT24_FLAG_READONLY | AT24_FLAG_IRUGO) },
 119         { "24c04", AT24_DEVICE_MAGIC(4096 / 8, 0) },
 120         /* 24rf08 quirk is handled at i2c-core */
 121         { "24c08", AT24_DEVICE_MAGIC(8192 / 8, 0) },
 122         { "24c16", AT24_DEVICE_MAGIC(16384 / 8, 0) },
 123         { "24c32", AT24_DEVICE_MAGIC(32768 / 8, AT24_FLAG_ADDR16) },
 124         { "24c64", AT24_DEVICE_MAGIC(65536 / 8, AT24_FLAG_ADDR16) },
 125         { "24c128", AT24_DEVICE_MAGIC(131072 / 8, AT24_FLAG_ADDR16) },
 126         { "24c256", AT24_DEVICE_MAGIC(262144 / 8, AT24_FLAG_ADDR16) },
 127         { "24c512", AT24_DEVICE_MAGIC(524288 / 8, AT24_FLAG_ADDR16) },
 128         { "24c1024", AT24_DEVICE_MAGIC(1048576 / 8, AT24_FLAG_ADDR16) },
 129         { "at24", 0 },
 130         { /* END OF LIST */ }
 131 };
 132 MODULE_DEVICE_TABLE(i2c, at24_ids);
 133
 134 /*-------------------------------------------------------------------------*/
 135
 136 /*
 137  * This routine supports chips which consume multiple I2C addresses. It
 138  * computes the addressing information to be used for a given r/w request.
 139  * Assumes that sanity checks for offset happened at sysfs-layer.
 140  */
 141 static struct i2c_client *at24_translate_offset(struct at24_data *at24,
 142                 unsigned *offset)
 143 {
 144         unsigned i;
 145
 146         if (at24->chip.flags & AT24_FLAG_ADDR16) {
 147                 i = *offset >> 16;
 148                 *offset &= 0xffff;
 149         } else {
 150                 i = *offset >> 8;
 151                 *offset &= 0xff;
 152         }
 153
 154         return at24->client[i];
 155 }
 156
 157 static ssize_t at24_eeprom_read(struct at24_data *at24, char *buf,
 158                 unsigned offset, size_t count)
 159 {
 160         struct i2c_msg msg[2];
 161         u8 msgbuf[2];
 162         struct i2c_client *client;
 163         unsigned long timeout, read_time;
 164         int status, i;
 165
 166         memset(msg, 0, sizeof(msg));
 167
 168         /*
 169          * REVISIT some multi-address chips don't rollover page reads to
 170          * the next slave address, so we may need to truncate the count.
 171          * Those chips might need another quirk flag.
 172          *
 173          * If the real hardware used four adjacent 24c02 chips and that
 174          * were misconfigured as one 24c08, that would be a similar effect:
 175          * one "eeprom" file not four, but larger reads would fail when
 176          * they crossed certain pages.
 177          */
 178
 179         /*
 180          * Slave address and byte offset derive from the offset. Always
 181          * set the byte address; on a multi-master board, another master
 182          * may have changed the chip's "current" address pointer.
 183          */
 184         client = at24_translate_offset(at24, &offset);
 185
 186         if (count > io_limit)
 187                 count = io_limit;
 188
 189         switch (at24->use_smbus) {
 190         case I2C_SMBUS_I2C_BLOCK_DATA:
 191                 /* Smaller eeproms can work given some SMBus extension calls */
 192                 if (count > I2C_SMBUS_BLOCK_MAX)
 193                         count = I2C_SMBUS_BLOCK_MAX;
 194                 break;
 195         case I2C_SMBUS_WORD_DATA:
 196                 count = 2;
 197                 break;
 198         case I2C_SMBUS_BYTE_DATA:
 199                 count = 1;
 200                 break;
 201         default:
 202                 /*
 203                  * When we have a better choice than SMBus calls, use a
 204                  * combined I2C message. Write address; then read up to
 205                  * io_limit data bytes. Note that read page rollover helps us
 206                  * here (unlike writes). msgbuf is u8 and will cast to our
 207                  * needs.
 208                  */
 209                 i = 0;
 210                 if (at24->chip.flags & AT24_FLAG_ADDR16)
 211                         msgbuf[i++] = offset >> 8;
 212                 msgbuf[i++] = offset;
 213
 214                 msg[0].addr = client->addr;
 215                 msg[0].buf = msgbuf;
 216                 msg[0].len = i;
 217
 218                 msg[1].addr = client->addr;
 219                 msg[1].flags = I2C_M_RD;
 220                 msg[1].buf = buf;
 221                 msg[1].len = count;
 222         }
 223
 224         /*
 225          * Reads fail if the previous write didn't complete yet. We may
 226          * loop a few times until this one succeeds, waiting at least
 227          * long enough for one entire page write to work.
 228          */
 229         timeout = jiffies + msecs_to_jiffies(write_timeout);
 230         do {
 231                 read_time = jiffies;
 232                 switch (at24->use_smbus) {
 233                 case I2C_SMBUS_I2C_BLOCK_DATA:
 234                         status = i2c_smbus_read_i2c_block_data(client, offset,
 235                                         count, buf);
 236                         break;
 237                 case I2C_SMBUS_WORD_DATA:
 238                         status = i2c_smbus_read_word_data(client, offset);
 239                         if (status >= 0) {
 240                                 buf[0] = status & 0xff;
 241                                 buf[1] = status >> 8;
 242                                 status = count;
 243                         }
 244                         break;
 245                 case I2C_SMBUS_BYTE_DATA:
 246                         status = i2c_smbus_read_byte_data(client, offset);
 247                         if (status >= 0) {
 248                                 buf[0] = status;
 249                                 status = count;
 250                         }
 251                         break;
 252                 default:
 253                         status = i2c_transfer(client->adapter, msg, 2);
 254                         if (status == 2)
 255                                 status = count;
 256                 }
 257                 dev_dbg(&client->dev, "read %zu@%d --> %d (%ld)\n",
 258                                 count, offset, status, jiffies);
 259
 260                 if (status == count)
 261                         return count;
 262
 263                 /* REVISIT: at HZ=100, this is sloooow */
 264                 msleep(1);
 265         } while (time_before(read_time, timeout));
 266
 267         return -ETIMEDOUT;
 268 }
 269
 270 static ssize_t at24_read(struct at24_data *at24,
 271                 char *buf, loff_t off, size_t count)
 272 {
 273         ssize_t retval = 0;
 274
 275         if (unlikely(!count))
 276                 return count;
 277
 278         /*
 279          * Read data from chip, protecting against concurrent updates
 280          * from this host, but not from other I2C masters.
 281          */
 282         mutex_lock(&at24->lock);
 283
 284         while (count) {
 285                 ssize_t status;
 286
 287                 status = at24_eeprom_read(at24, buf, off, count);
 288                 if (status <= 0) {
 289                         if (retval == 0)
 290                                 retval = status;
 291                         break;
 292                 }
 293                 buf += status;
 294                 off += status;
 295                 count -= status;
 296                 retval += status;
 297         }
 298
 299         mutex_unlock(&at24->lock);
 300
 301         return retval;
 302 }
 303
 304 static ssize_t at24_bin_read(struct file *filp, struct kobject *kobj,
 305                 struct bin_attribute *attr,
 306                 char *buf, loff_t off, size_t count)
 307 {
 308         struct at24_data *at24;
 309
 310         at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
 311         return at24_read(at24, buf, off, count);
 312 }
 313
 314
 315 /*
 316  * Note that if the hardware write-protect pin is pulled high, the whole
 317  * chip is normally write protected. But there are plenty of product
 318  * variants here, including OTP fuses and partial chip protect.
 319  *
 320  * We only use page mode writes; the alternative is sloooow. This routine
 321  * writes at most one page.
 322  */
 323 static ssize_t at24_eeprom_write(struct at24_data *at24, const char *buf,
 324                 unsigned offset, size_t count)
 325 {
 326         struct i2c_client *client;
 327         struct i2c_msg msg;
 328         ssize_t status = 0;
 329         unsigned long timeout, write_time;
 330         unsigned next_page;
 331
 332         /* Get corresponding I2C address and adjust offset */
 333         client = at24_translate_offset(at24, &offset);
 334
 335         /* write_max is at most a page */
 336         if (count > at24->write_max)
 337                 count = at24->write_max;
 338
 339         /* Never roll over backwards, to the start of this page */
 340         next_page = roundup(offset + 1, at24->chip.page_size);
 341         if (offset + count > next_page)
 342                 count = next_page - offset;
 343
 344         /* If we'll use I2C calls for I/O, set up the message */
 345         if (!at24->use_smbus) {
 346                 int i = 0;
 347
 348                 msg.addr = client->addr;
 349                 msg.flags = 0;
 350
 351                 /* msg.buf is u8 and casts will mask the values */
 352                 msg.buf = at24->writebuf;
 353                 if (at24->chip.flags & AT24_FLAG_ADDR16)
 354                         msg.buf[i++] = offset >> 8;
 355
 356                 msg.buf[i++] = offset;
 357                 memcpy(&msg.buf[i], buf, count);
 358                 msg.len = i + count;
 359         }
 360
 361         /*
 362          * Writes fail if the previous one didn't complete yet. We may
 363          * loop a few times until this one succeeds, waiting at least
 364          * long enough for one entire page write to work.
 365          */
 366         timeout = jiffies + msecs_to_jiffies(write_timeout);
 367         do {
 368                 write_time = jiffies;
 369                 if (at24->use_smbus_write) {
 370                         switch (at24->use_smbus_write) {
 371                         case I2C_SMBUS_I2C_BLOCK_DATA:
 372                                 status = i2c_smbus_write_i2c_block_data(client,
 373                                                 offset, count, buf);
 374                                 break;
 375                         case I2C_SMBUS_BYTE_DATA:
 376                                 status = i2c_smbus_write_byte_data(client,
 377                                                 offset, buf[0]);
 378                                 break;
 379                         }
 380
 381                         if (status == 0)
 382                                 status = count;
 383                 } else {
 384                         status = i2c_transfer(client->adapter, &msg, 1);
 385                         if (status == 1)
 386                                 status = count;
 387                 }
 388                 dev_dbg(&client->dev, "write %zu@%d --> %zd (%ld)\n",
 389                                 count, offset, status, jiffies);
 390
 391                 if (status == count)
 392                         return count;
 393
 394                 /* REVISIT: at HZ=100, this is sloooow */
 395                 msleep(1);
 396         } while (time_before(write_time, timeout));
 397
 398         return -ETIMEDOUT;
 399 }
 400
 401 static ssize_t at24_write(struct at24_data *at24, const char *buf, loff_t off,
 402                           size_t count)
 403 {
 404         ssize_t retval = 0;
 405
 406         if (unlikely(!count))
 407                 return count;
 408
 409         /*
 410          * Write data to chip, protecting against concurrent updates
 411          * from this host, but not from other I2C masters.
 412          */
 413         mutex_lock(&at24->lock);
 414
 415         while (count) {
 416                 ssize_t status;
 417
 418                 status = at24_eeprom_write(at24, buf, off, count);
 419                 if (status <= 0) {
 420                         if (retval == 0)
 421                                 retval = status;
 422                         break;
 423                 }
 424                 buf += status;
 425                 off += status;
 426                 count -= status;
 427                 retval += status;
 428         }
 429
 430         mutex_unlock(&at24->lock);
 431
 432         return retval;
 433 }
 434
 435 static ssize_t at24_bin_write(struct file *filp, struct kobject *kobj,
 436                 struct bin_attribute *attr,
 437                 char *buf, loff_t off, size_t count)
 438 {
 439         struct at24_data *at24;
 440
 441         if (unlikely(off >= attr->size))
 442                 return -EFBIG;
 443
 444         at24 = dev_get_drvdata(container_of(kobj, struct device, kobj));
 445         return at24_write(at24, buf, off, count);
 446 }
 447
 448 /*-------------------------------------------------------------------------*/
 449
 450 /*
 451  * This lets other kernel code access the eeprom data. For example, it
 452  * might hold a board's Ethernet address, or board-specific calibration
 453  * data generated on the manufacturing floor.
 454  */
 455
 456 static ssize_t at24_macc_read(struct memory_accessor *macc, char *buf,
 457                          off_t offset, size_t count)
 458 {
 459         struct at24_data *at24 = container_of(macc, struct at24_data, macc);
 460
 461         return at24_read(at24, buf, offset, count);
 462 }
 463
 464 static ssize_t at24_macc_write(struct memory_accessor *macc, const char *buf,
 465                           off_t offset, size_t count)
 466 {
 467         struct at24_data *at24 = container_of(macc, struct at24_data, macc);
 468
 469         return at24_write(at24, buf, offset, count);
 470 }
 471
 472 /*-------------------------------------------------------------------------*/
 473
 474 #ifdef CONFIG_OF
 475 static void at24_get_ofdata(struct i2c_client *client,
 476                 struct at24_platform_data *chip)
 477 {
 478         const __be32 *val;
 479         struct device_node *node = client->dev.of_node;
 480
 481         if (node) {
 482                 if (of_get_property(node, "read-only", NULL))
 483                         chip->flags |= AT24_FLAG_READONLY;
 484                 val = of_get_property(node, "pagesize", NULL);
 485                 if (val)
 486                         chip->page_size = be32_to_cpup(val);
 487         }
 488 }
 489 #else
 490 static void at24_get_ofdata(struct i2c_client *client,
 491                 struct at24_platform_data *chip)
 492 { }
 493 #endif /* CONFIG_OF */
 494
 495 static int at24_probe(struct i2c_client *client, const struct i2c_device_id *id)
 496 {
 497         struct at24_platform_data chip;
 498         bool writable;
 499         int use_smbus = 0;
 500         int use_smbus_write = 0;
 501         struct at24_data *at24;
 502         int err;
 503         unsigned i, num_addresses;
 504         kernel_ulong_t magic;
 505
 506         if (client->dev.platform_data) {
 507                 chip = *(struct at24_platform_data *)client->dev.platform_data;
 508         } else {
 509                 if (!id->driver_data)
 510                         return -ENODEV;
 511
 512                 magic = id->driver_data;
 513                 chip.byte_len = BIT(magic & AT24_BITMASK(AT24_SIZE_BYTELEN));
 514                 magic >>= AT24_SIZE_BYTELEN;
 515                 chip.flags = magic & AT24_BITMASK(AT24_SIZE_FLAGS);
 516                 /*
 517                  * This is slow, but we can't know all eeproms, so we better
 518                  * play safe. Specifying custom eeprom-types via platform_data
 519                  * is recommended anyhow.
 520                  */
 521                 chip.page_size = 1;
 522
 523                 /* update chipdata if OF is present */
 524                 at24_get_ofdata(client, &chip);
 525
 526                 chip.setup = NULL;
 527                 chip.context = NULL;
 528         }
 529
 530         if (!is_power_of_2(chip.byte_len))
 531                 dev_warn(&client->dev,
 532                         "byte_len looks suspicious (no power of 2)!\n");
 533         if (!chip.page_size) {
 534                 dev_err(&client->dev, "page_size must not be 0!\n");
 535                 return -EINVAL;
 536         }
 537         if (!is_power_of_2(chip.page_size))
 538                 dev_warn(&client->dev,
 539                         "page_size looks suspicious (no power of 2)!\n");
 540
 541         /* Use I2C operations unless we're stuck with SMBus extensions. */
 542         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
 543                 if (chip.flags & AT24_FLAG_ADDR16)
 544                         return -EPFNOSUPPORT;
 545
 546                 if (i2c_check_functionality(client->adapter,
 547                                 I2C_FUNC_SMBUS_READ_I2C_BLOCK)) {
 548                         use_smbus = I2C_SMBUS_I2C_BLOCK_DATA;
 549                 } else if (i2c_check_functionality(client->adapter,
 550                                 I2C_FUNC_SMBUS_READ_WORD_DATA)) {
 551                         use_smbus = I2C_SMBUS_WORD_DATA;
 552                 } else if (i2c_check_functionality(client->adapter,
 553                                 I2C_FUNC_SMBUS_READ_BYTE_DATA)) {
 554                         use_smbus = I2C_SMBUS_BYTE_DATA;
 555                 } else {
 556                         return -EPFNOSUPPORT;
 557                 }
 558         }
 559
 560         /* Use I2C operations unless we're stuck with SMBus extensions. */
 561         if (!i2c_check_functionality(client->adapter, I2C_FUNC_I2C)) {
 562                 if (i2c_check_functionality(client->adapter,
 563                                 I2C_FUNC_SMBUS_WRITE_I2C_BLOCK)) {
 564                         use_smbus_write = I2C_SMBUS_I2C_BLOCK_DATA;
 565                 } else if (i2c_check_functionality(client->adapter,
 566                                 I2C_FUNC_SMBUS_WRITE_BYTE_DATA)) {
 567                         use_smbus_write = I2C_SMBUS_BYTE_DATA;
 568                         chip.page_size = 1;
 569                 }
 570         }
 571
 572         if (chip.flags & AT24_FLAG_TAKE8ADDR)
 573                 num_addresses = 8;
 574         else
 575                 num_addresses = DIV_ROUND_UP(chip.byte_len,
 576                         (chip.flags & AT24_FLAG_ADDR16) ? 65536 : 256);
 577
 578         at24 = devm_kzalloc(&client->dev, sizeof(struct at24_data) +
 579                 num_addresses * sizeof(struct i2c_client *), GFP_KERNEL);
 580         if (!at24)
 581                 return -ENOMEM;
 582
 583         mutex_init(&at24->lock);
 584         at24->use_smbus = use_smbus;
 585         at24->use_smbus_write = use_smbus_write;
 586         at24->chip = chip;
 587         at24->num_addresses = num_addresses;
 588
 589         /*
 590          * Export the EEPROM bytes through sysfs, since that's convenient.
 591          * By default, only root should see the data (maybe passwords etc)
 592          */
 593         sysfs_bin_attr_init(&at24->bin);
 594         at24->bin.attr.name = "eeprom";
 595         at24->bin.attr.mode = chip.flags & AT24_FLAG_IRUGO ? S_IRUGO : S_IRUSR;
 596         at24->bin.read = at24_bin_read;
 597         at24->bin.size = chip.byte_len;
 598
 599         at24->macc.read = at24_macc_read;
 600
 601         writable = !(chip.flags & AT24_FLAG_READONLY);
 602         if (writable) {
 603                 if (!use_smbus || use_smbus_write) {
 604
 605                         unsigned write_max = chip.page_size;
 606
 607                         at24->macc.write = at24_macc_write;
 608
 609                         at24->bin.write = at24_bin_write;
 610                         at24->bin.attr.mode |= S_IWUSR;
 611
 612                         if (write_max > io_limit)
 613                                 write_max = io_limit;
 614                         if (use_smbus && write_max > I2C_SMBUS_BLOCK_MAX)
 615                                 write_max = I2C_SMBUS_BLOCK_MAX;
 616                         at24->write_max = write_max;
 617
 618                         /* buffer (data + address at the beginning) */
 619                         at24->writebuf = devm_kzalloc(&client->dev,
 620                                 write_max + 2, GFP_KERNEL);
 621                         if (!at24->writebuf)
 622                                 return -ENOMEM;
 623                 } else {
 624                         dev_warn(&client->dev,
 625                                 "cannot write due to controller restrictions.");
 626                 }
 627         }
 628
 629         at24->client[0] = client;
 630
 631         /* use dummy devices for multiple-address chips */
 632         for (i = 1; i < num_addresses; i++) {
 633                 at24->client[i] = i2c_new_dummy(client->adapter,
 634                                         client->addr + i);
 635                 if (!at24->client[i]) {
 636                         dev_err(&client->dev, "address 0x%02x unavailable\n",
 637                                         client->addr + i);
 638                         err = -EADDRINUSE;
 639                         goto err_clients;
 640                 }
 641         }
 642
 643         err = sysfs_create_bin_file(&client->dev.kobj, &at24->bin);
 644         if (err)
 645                 goto err_clients;
 646
 647         i2c_set_clientdata(client, at24);
 648
 649         dev_info(&client->dev, "%zu byte %s EEPROM, %s, %u bytes/write\n",
 650                 at24->bin.size, client->name,
 651                 writable ? "writable" : "read-only", at24->write_max);
 652         if (use_smbus == I2C_SMBUS_WORD_DATA ||
 653             use_smbus == I2C_SMBUS_BYTE_DATA) {
 654                 dev_notice(&client->dev, "Falling back to %s reads, "
 655                            "performance will suffer\n", use_smbus ==
 656                            I2C_SMBUS_WORD_DATA ? "word" : "byte");
 657         }
 658
 659         /* export data to kernel code */
 660         if (chip.setup)
 661                 chip.setup(&at24->macc, chip.context);
 662
 663         return 0;
 664
 665 err_clients:
 666         for (i = 1; i < num_addresses; i++)
 667                 if (at24->client[i])
 668                         i2c_unregister_device(at24->client[i]);
 669
 670         return err;
 671 }
 672
 673 static int at24_remove(struct i2c_client *client)
 674 {
 675         struct at24_data *at24;
 676         int i;
 677
 678         at24 = i2c_get_clientdata(client);
 679         sysfs_remove_bin_file(&client->dev.kobj, &at24->bin);
 680
 681         for (i = 1; i < at24->num_addresses; i++)
 682                 i2c_unregister_device(at24->client[i]);
 683
 684         return 0;
 685 }
 686
 687 /*-------------------------------------------------------------------------*/
 688
 689 static struct i2c_driver at24_driver = {
 690         .driver = {
 691                 .name = "at24",
 692                 .owner = THIS_MODULE,
 693         },
 694         .probe = at24_probe,
 695         .remove = at24_remove,
 696         .id_table = at24_ids,
 697 };
 698
 699 static int __init at24_init(void)
 700 {
 701         if (!io_limit) {
 702                 pr_err("at24: io_limit must not be 0!\n");
 703                 return -EINVAL;
 704         }
 705
 706         io_limit = rounddown_pow_of_two(io_limit);
 707         return i2c_add_driver(&at24_driver);
 708 }
 709 module_init(at24_init);
 710
 711 static void __exit at24_exit(void)
 712 {
 713         i2c_del_driver(&at24_driver);
 714 }
 715 module_exit(at24_exit);
 716
 717 MODULE_DESCRIPTION("Driver for most I2C EEPROMs");
 718 MODULE_AUTHOR("David Brownell and Wolfram Sang");
 719 MODULE_LICENSE("GPL");