drivers/iio/magnetometer/ak8975.c

   1 /*
   2  * A sensor driver for the magnetometer AK8975.
   3  *
   4  * Magnetic compass sensor driver for monitoring magnetic flux information.
   5  *
   6  * Copyright (c) 2010, NVIDIA Corporation.
   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, but WITHOUT
  14  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  15  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
  16  * more details.
  17  *
  18  * You should have received a copy of the GNU General Public License along
  19  * with this program; if not, write to the Free Software Foundation, Inc.,
  20  * 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  21  */
  22
  23 #include <linux/module.h>
  24 #include <linux/kernel.h>
  25 #include <linux/slab.h>
  26 #include <linux/i2c.h>
  27 #include <linux/interrupt.h>
  28 #include <linux/err.h>
  29 #include <linux/mutex.h>
  30 #include <linux/delay.h>
  31 #include <linux/bitops.h>
  32 #include <linux/gpio.h>
  33 #include <linux/of_gpio.h>
  34 #include <linux/acpi.h>
  35
  36 #include <linux/iio/iio.h>
  37 #include <linux/iio/sysfs.h>
  38 /*
  39  * Register definitions, as well as various shifts and masks to get at the
  40  * individual fields of the registers.
  41  */
  42 #define AK8975_REG_WIA                  0x00
  43 #define AK8975_DEVICE_ID                0x48
  44
  45 #define AK8975_REG_INFO                 0x01
  46
  47 #define AK8975_REG_ST1                  0x02
  48 #define AK8975_REG_ST1_DRDY_SHIFT       0
  49 #define AK8975_REG_ST1_DRDY_MASK        (1 << AK8975_REG_ST1_DRDY_SHIFT)
  50
  51 #define AK8975_REG_HXL                  0x03
  52 #define AK8975_REG_HXH                  0x04
  53 #define AK8975_REG_HYL                  0x05
  54 #define AK8975_REG_HYH                  0x06
  55 #define AK8975_REG_HZL                  0x07
  56 #define AK8975_REG_HZH                  0x08
  57 #define AK8975_REG_ST2                  0x09
  58 #define AK8975_REG_ST2_DERR_SHIFT       2
  59 #define AK8975_REG_ST2_DERR_MASK        (1 << AK8975_REG_ST2_DERR_SHIFT)
  60
  61 #define AK8975_REG_ST2_HOFL_SHIFT       3
  62 #define AK8975_REG_ST2_HOFL_MASK        (1 << AK8975_REG_ST2_HOFL_SHIFT)
  63
  64 #define AK8975_REG_CNTL                 0x0A
  65 #define AK8975_REG_CNTL_MODE_SHIFT      0
  66 #define AK8975_REG_CNTL_MODE_MASK       (0xF << AK8975_REG_CNTL_MODE_SHIFT)
  67 #define AK8975_REG_CNTL_MODE_POWER_DOWN 0
  68 #define AK8975_REG_CNTL_MODE_ONCE       1
  69 #define AK8975_REG_CNTL_MODE_SELF_TEST  8
  70 #define AK8975_REG_CNTL_MODE_FUSE_ROM   0xF
  71
  72 #define AK8975_REG_RSVC                 0x0B
  73 #define AK8975_REG_ASTC                 0x0C
  74 #define AK8975_REG_TS1                  0x0D
  75 #define AK8975_REG_TS2                  0x0E
  76 #define AK8975_REG_I2CDIS               0x0F
  77 #define AK8975_REG_ASAX                 0x10
  78 #define AK8975_REG_ASAY                 0x11
  79 #define AK8975_REG_ASAZ                 0x12
  80
  81 #define AK8975_MAX_REGS                 AK8975_REG_ASAZ
  82
  83 /*
  84  * Miscellaneous values.
  85  */
  86 #define AK8975_MAX_CONVERSION_TIMEOUT   500
  87 #define AK8975_CONVERSION_DONE_POLL_TIME 10
  88 #define AK8975_DATA_READY_TIMEOUT       ((100*HZ)/1000)
  89 #define RAW_TO_GAUSS_8975(asa) ((((asa) + 128) * 3000) / 256)
  90 #define RAW_TO_GAUSS_8963(asa) ((((asa) + 128) * 6000) / 256)
  91
  92 /* Compatible Asahi Kasei Compass parts */
  93 enum asahi_compass_chipset {
  94         AK8975,
  95         AK8963,
  96 };
  97
  98 /*
  99  * Per-instance context data for the device.
 100  */
 101 struct ak8975_data {
 102         struct i2c_client       *client;
 103         struct attribute_group  attrs;
 104         struct mutex            lock;
 105         u8                      asa[3];
 106         long                    raw_to_gauss[3];
 107         u8                      reg_cache[AK8975_MAX_REGS];
 108         int                     eoc_gpio;
 109         int                     eoc_irq;
 110         wait_queue_head_t       data_ready_queue;
 111         unsigned long           flags;
 112         enum asahi_compass_chipset chipset;
 113 };
 114
 115 static const int ak8975_index_to_reg[] = {
 116         AK8975_REG_HXL, AK8975_REG_HYL, AK8975_REG_HZL,
 117 };
 118
 119 /*
 120  * Helper function to write to the I2C device's registers.
 121  */
 122 static int ak8975_write_data(struct i2c_client *client,
 123                              u8 reg, u8 val, u8 mask, u8 shift)
 124 {
 125         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 126         struct ak8975_data *data = iio_priv(indio_dev);
 127         u8 regval;
 128         int ret;
 129
 130         regval = (data->reg_cache[reg] & ~mask) | (val << shift);
 131         ret = i2c_smbus_write_byte_data(client, reg, regval);
 132         if (ret < 0) {
 133                 dev_err(&client->dev, "Write to device fails status %x\n", ret);
 134                 return ret;
 135         }
 136         data->reg_cache[reg] = regval;
 137
 138         return 0;
 139 }
 140
 141 /*
 142  * Handle data ready irq
 143  */
 144 static irqreturn_t ak8975_irq_handler(int irq, void *data)
 145 {
 146         struct ak8975_data *ak8975 = data;
 147
 148         set_bit(0, &ak8975->flags);
 149         wake_up(&ak8975->data_ready_queue);
 150
 151         return IRQ_HANDLED;
 152 }
 153
 154 /*
 155  * Install data ready interrupt handler
 156  */
 157 static int ak8975_setup_irq(struct ak8975_data *data)
 158 {
 159         struct i2c_client *client = data->client;
 160         int rc;
 161         int irq;
 162
 163         if (client->irq)
 164                 irq = client->irq;
 165         else
 166                 irq = gpio_to_irq(data->eoc_gpio);
 167
 168         rc = request_irq(irq, ak8975_irq_handler,
 169                          IRQF_TRIGGER_RISING | IRQF_ONESHOT,
 170                          dev_name(&client->dev), data);
 171         if (rc < 0) {
 172                 dev_err(&client->dev,
 173                         "irq %d request failed, (gpio %d): %d\n",
 174                         irq, data->eoc_gpio, rc);
 175                 return rc;
 176         }
 177
 178         init_waitqueue_head(&data->data_ready_queue);
 179         clear_bit(0, &data->flags);
 180         data->eoc_irq = irq;
 181
 182         return rc;
 183 }
 184
 185
 186 /*
 187  * Perform some start-of-day setup, including reading the asa calibration
 188  * values and caching them.
 189  */
 190 static int ak8975_setup(struct i2c_client *client)
 191 {
 192         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 193         struct ak8975_data *data = iio_priv(indio_dev);
 194         u8 device_id;
 195         int ret;
 196
 197         /* Confirm that the device we're talking to is really an AK8975. */
 198         ret = i2c_smbus_read_byte_data(client, AK8975_REG_WIA);
 199         if (ret < 0) {
 200                 dev_err(&client->dev, "Error reading WIA\n");
 201                 return ret;
 202         }
 203         device_id = ret;
 204         if (device_id != AK8975_DEVICE_ID) {
 205                 dev_err(&client->dev, "Device ak8975 not found\n");
 206                 return -ENODEV;
 207         }
 208
 209         /* Write the fused rom access mode. */
 210         ret = ak8975_write_data(client,
 211                                 AK8975_REG_CNTL,
 212                                 AK8975_REG_CNTL_MODE_FUSE_ROM,
 213                                 AK8975_REG_CNTL_MODE_MASK,
 214                                 AK8975_REG_CNTL_MODE_SHIFT);
 215         if (ret < 0) {
 216                 dev_err(&client->dev, "Error in setting fuse access mode\n");
 217                 return ret;
 218         }
 219
 220         /* Get asa data and store in the device data. */
 221         ret = i2c_smbus_read_i2c_block_data(client, AK8975_REG_ASAX,
 222                                             3, data->asa);
 223         if (ret < 0) {
 224                 dev_err(&client->dev, "Not able to read asa data\n");
 225                 return ret;
 226         }
 227
 228         /* After reading fuse ROM data set power-down mode */
 229         ret = ak8975_write_data(client,
 230                                 AK8975_REG_CNTL,
 231                                 AK8975_REG_CNTL_MODE_POWER_DOWN,
 232                                 AK8975_REG_CNTL_MODE_MASK,
 233                                 AK8975_REG_CNTL_MODE_SHIFT);
 234
 235         if (data->eoc_gpio > 0 || client->irq) {
 236                 ret = ak8975_setup_irq(data);
 237                 if (ret < 0) {
 238                         dev_err(&client->dev,
 239                                 "Error setting data ready interrupt\n");
 240                         return ret;
 241                 }
 242         }
 243
 244         if (ret < 0) {
 245                 dev_err(&client->dev, "Error in setting power-down mode\n");
 246                 return ret;
 247         }
 248
 249 /*
 250  * Precalculate scale factor (in Gauss units) for each axis and
 251  * store in the device data.
 252  *
 253  * This scale factor is axis-dependent, and is derived from 3 calibration
 254  * factors ASA(x), ASA(y), and ASA(z).
 255  *
 256  * These ASA values are read from the sensor device at start of day, and
 257  * cached in the device context struct.
 258  *
 259  * Adjusting the flux value with the sensitivity adjustment value should be
 260  * done via the following formula:
 261  *
 262  * Hadj = H * ( ( ( (ASA-128)*0.5 ) / 128 ) + 1 )
 263  *
 264  * where H is the raw value, ASA is the sensitivity adjustment, and Hadj
 265  * is the resultant adjusted value.
 266  *
 267  * We reduce the formula to:
 268  *
 269  * Hadj = H * (ASA + 128) / 256
 270  *
 271  * H is in the range of -4096 to 4095.  The magnetometer has a range of
 272  * +-1229uT.  To go from the raw value to uT is:
 273  *
 274  * HuT = H * 1229/4096, or roughly, 3/10.
 275  *
 276  * Since 1uT = 0.01 gauss, our final scale factor becomes:
 277  *
 278  * Hadj = H * ((ASA + 128) / 256) * 3/10 * 1/100
 279  * Hadj = H * ((ASA + 128) * 0.003) / 256
 280  *
 281  * Since ASA doesn't change, we cache the resultant scale factor into the
 282  * device context in ak8975_setup().
 283  */
 284         if (data->chipset == AK8963) {
 285                 /*
 286                  * H range is +-8190 and magnetometer range is +-4912.
 287                  * So HuT using the above explanation for 8975,
 288                  * 4912/8190 = ~ 6/10.
 289                  * So the Hadj should use 6/10 instead of 3/10.
 290                  */
 291                 data->raw_to_gauss[0] = RAW_TO_GAUSS_8963(data->asa[0]);
 292                 data->raw_to_gauss[1] = RAW_TO_GAUSS_8963(data->asa[1]);
 293                 data->raw_to_gauss[2] = RAW_TO_GAUSS_8963(data->asa[2]);
 294         } else {
 295                 data->raw_to_gauss[0] = RAW_TO_GAUSS_8975(data->asa[0]);
 296                 data->raw_to_gauss[1] = RAW_TO_GAUSS_8975(data->asa[1]);
 297                 data->raw_to_gauss[2] = RAW_TO_GAUSS_8975(data->asa[2]);
 298         }
 299
 300         return 0;
 301 }
 302
 303 static int wait_conversion_complete_gpio(struct ak8975_data *data)
 304 {
 305         struct i2c_client *client = data->client;
 306         u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
 307         int ret;
 308
 309         /* Wait for the conversion to complete. */
 310         while (timeout_ms) {
 311                 msleep(AK8975_CONVERSION_DONE_POLL_TIME);
 312                 if (gpio_get_value(data->eoc_gpio))
 313                         break;
 314                 timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
 315         }
 316         if (!timeout_ms) {
 317                 dev_err(&client->dev, "Conversion timeout happened\n");
 318                 return -EINVAL;
 319         }
 320
 321         ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
 322         if (ret < 0)
 323                 dev_err(&client->dev, "Error in reading ST1\n");
 324
 325         return ret;
 326 }
 327
 328 static int wait_conversion_complete_polled(struct ak8975_data *data)
 329 {
 330         struct i2c_client *client = data->client;
 331         u8 read_status;
 332         u32 timeout_ms = AK8975_MAX_CONVERSION_TIMEOUT;
 333         int ret;
 334
 335         /* Wait for the conversion to complete. */
 336         while (timeout_ms) {
 337                 msleep(AK8975_CONVERSION_DONE_POLL_TIME);
 338                 ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST1);
 339                 if (ret < 0) {
 340                         dev_err(&client->dev, "Error in reading ST1\n");
 341                         return ret;
 342                 }
 343                 read_status = ret;
 344                 if (read_status)
 345                         break;
 346                 timeout_ms -= AK8975_CONVERSION_DONE_POLL_TIME;
 347         }
 348         if (!timeout_ms) {
 349                 dev_err(&client->dev, "Conversion timeout happened\n");
 350                 return -EINVAL;
 351         }
 352
 353         return read_status;
 354 }
 355
 356 /* Returns 0 if the end of conversion interrupt occured or -ETIME otherwise */
 357 static int wait_conversion_complete_interrupt(struct ak8975_data *data)
 358 {
 359         int ret;
 360
 361         ret = wait_event_timeout(data->data_ready_queue,
 362                                  test_bit(0, &data->flags),
 363                                  AK8975_DATA_READY_TIMEOUT);
 364         clear_bit(0, &data->flags);
 365
 366         return ret > 0 ? 0 : -ETIME;
 367 }
 368
 369 /*
 370  * Emits the raw flux value for the x, y, or z axis.
 371  */
 372 static int ak8975_read_axis(struct iio_dev *indio_dev, int index, int *val)
 373 {
 374         struct ak8975_data *data = iio_priv(indio_dev);
 375         struct i2c_client *client = data->client;
 376         u16 meas_reg;
 377         s16 raw;
 378         int ret;
 379
 380         mutex_lock(&data->lock);
 381
 382         /* Set up the device for taking a sample. */
 383         ret = ak8975_write_data(client,
 384                                 AK8975_REG_CNTL,
 385                                 AK8975_REG_CNTL_MODE_ONCE,
 386                                 AK8975_REG_CNTL_MODE_MASK,
 387                                 AK8975_REG_CNTL_MODE_SHIFT);
 388         if (ret < 0) {
 389                 dev_err(&client->dev, "Error in setting operating mode\n");
 390                 goto exit;
 391         }
 392
 393         /* Wait for the conversion to complete. */
 394         if (data->eoc_irq)
 395                 ret = wait_conversion_complete_interrupt(data);
 396         else if (gpio_is_valid(data->eoc_gpio))
 397                 ret = wait_conversion_complete_gpio(data);
 398         else
 399                 ret = wait_conversion_complete_polled(data);
 400         if (ret < 0)
 401                 goto exit;
 402
 403         /* This will be executed only for non-interrupt based waiting case */
 404         if (ret & AK8975_REG_ST1_DRDY_MASK) {
 405                 ret = i2c_smbus_read_byte_data(client, AK8975_REG_ST2);
 406                 if (ret < 0) {
 407                         dev_err(&client->dev, "Error in reading ST2\n");
 408                         goto exit;
 409                 }
 410                 if (ret & (AK8975_REG_ST2_DERR_MASK |
 411                            AK8975_REG_ST2_HOFL_MASK)) {
 412                         dev_err(&client->dev, "ST2 status error 0x%x\n", ret);
 413                         ret = -EINVAL;
 414                         goto exit;
 415                 }
 416         }
 417
 418         /* Read the flux value from the appropriate register
 419            (the register is specified in the iio device attributes). */
 420         ret = i2c_smbus_read_word_data(client, ak8975_index_to_reg[index]);
 421         if (ret < 0) {
 422                 dev_err(&client->dev, "Read axis data fails\n");
 423                 goto exit;
 424         }
 425         meas_reg = ret;
 426
 427         mutex_unlock(&data->lock);
 428
 429         /* Endian conversion of the measured values. */
 430         raw = (s16) (le16_to_cpu(meas_reg));
 431
 432         /* Clamp to valid range. */
 433         raw = clamp_t(s16, raw, -4096, 4095);
 434         *val = raw;
 435         return IIO_VAL_INT;
 436
 437 exit:
 438         mutex_unlock(&data->lock);
 439         return ret;
 440 }
 441
 442 static int ak8975_read_raw(struct iio_dev *indio_dev,
 443                            struct iio_chan_spec const *chan,
 444                            int *val, int *val2,
 445                            long mask)
 446 {
 447         struct ak8975_data *data = iio_priv(indio_dev);
 448
 449         switch (mask) {
 450         case IIO_CHAN_INFO_RAW:
 451                 return ak8975_read_axis(indio_dev, chan->address, val);
 452         case IIO_CHAN_INFO_SCALE:
 453                 *val = 0;
 454                 *val2 = data->raw_to_gauss[chan->address];
 455                 return IIO_VAL_INT_PLUS_MICRO;
 456         }
 457         return -EINVAL;
 458 }
 459
 460 #define AK8975_CHANNEL(axis, index)                                     \
 461         {                                                               \
 462                 .type = IIO_MAGN,                                       \
 463                 .modified = 1,                                          \
 464                 .channel2 = IIO_MOD_##axis,                             \
 465                 .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |          \
 466                              BIT(IIO_CHAN_INFO_SCALE),                  \
 467                 .address = index,                                       \
 468         }
 469
 470 static const struct iio_chan_spec ak8975_channels[] = {
 471         AK8975_CHANNEL(X, 0), AK8975_CHANNEL(Y, 1), AK8975_CHANNEL(Z, 2),
 472 };
 473
 474 static const struct iio_info ak8975_info = {
 475         .read_raw = &ak8975_read_raw,
 476         .driver_module = THIS_MODULE,
 477 };
 478
 479 static const struct acpi_device_id ak_acpi_match[] = {
 480         {"AK8975", AK8975},
 481         {"AK8963", AK8963},
 482         {"INVN6500", AK8963},
 483         { },
 484 };
 485 MODULE_DEVICE_TABLE(acpi, ak_acpi_match);
 486
 487 static char *ak8975_match_acpi_device(struct device *dev,
 488                                 enum asahi_compass_chipset *chipset)
 489 {
 490         const struct acpi_device_id *id;
 491
 492         id = acpi_match_device(dev->driver->acpi_match_table, dev);
 493         if (!id)
 494                 return NULL;
 495         *chipset = (int)id->driver_data;
 496
 497         return (char *)dev_name(dev);
 498 }
 499
 500 static int ak8975_probe(struct i2c_client *client,
 501                         const struct i2c_device_id *id)
 502 {
 503         struct ak8975_data *data;
 504         struct iio_dev *indio_dev;
 505         int eoc_gpio;
 506         int err;
 507         char *name = NULL;
 508
 509         /* Grab and set up the supplied GPIO. */
 510         if (client->dev.platform_data)
 511                 eoc_gpio = *(int *)(client->dev.platform_data);
 512         else if (client->dev.of_node)
 513                 eoc_gpio = of_get_gpio(client->dev.of_node, 0);
 514         else
 515                 eoc_gpio = -1;
 516
 517         if (eoc_gpio == -EPROBE_DEFER)
 518                 return -EPROBE_DEFER;
 519
 520         /* We may not have a GPIO based IRQ to scan, that is fine, we will
 521            poll if so */
 522         if (gpio_is_valid(eoc_gpio)) {
 523                 err = gpio_request_one(eoc_gpio, GPIOF_IN, "ak_8975");
 524                 if (err < 0) {
 525                         dev_err(&client->dev,
 526                                 "failed to request GPIO %d, error %d\n",
 527                                                         eoc_gpio, err);
 528                         goto exit;
 529                 }
 530         }
 531
 532         /* Register with IIO */
 533         indio_dev = iio_device_alloc(sizeof(*data));
 534         if (indio_dev == NULL) {
 535                 err = -ENOMEM;
 536                 goto exit_gpio;
 537         }
 538         data = iio_priv(indio_dev);
 539         i2c_set_clientdata(client, indio_dev);
 540
 541         data->client = client;
 542         data->eoc_gpio = eoc_gpio;
 543         data->eoc_irq = 0;
 544
 545         /* id will be NULL when enumerated via ACPI */
 546         if (id) {
 547                 data->chipset =
 548                         (enum asahi_compass_chipset)(id->driver_data);
 549                 name = (char *) id->name;
 550         } else if (ACPI_HANDLE(&client->dev))
 551                 name = ak8975_match_acpi_device(&client->dev, &data->chipset);
 552         else {
 553                 err = -ENOSYS;
 554                 goto exit_free_iio;
 555         }
 556         dev_dbg(&client->dev, "Asahi compass chip %s\n", name);
 557
 558         /* Perform some basic start-of-day setup of the device. */
 559         err = ak8975_setup(client);
 560         if (err < 0) {
 561                 dev_err(&client->dev, "AK8975 initialization fails\n");
 562                 goto exit_free_iio;
 563         }
 564
 565         data->client = client;
 566         mutex_init(&data->lock);
 567         data->eoc_gpio = eoc_gpio;
 568         indio_dev->dev.parent = &client->dev;
 569         indio_dev->channels = ak8975_channels;
 570         indio_dev->num_channels = ARRAY_SIZE(ak8975_channels);
 571         indio_dev->info = &ak8975_info;
 572         indio_dev->modes = INDIO_DIRECT_MODE;
 573         indio_dev->name = name;
 574         err = iio_device_register(indio_dev);
 575         if (err < 0)
 576                 goto exit_free_iio;
 577
 578         return 0;
 579
 580 exit_free_iio:
 581         iio_device_free(indio_dev);
 582         if (data->eoc_irq)
 583                 free_irq(data->eoc_irq, data);
 584 exit_gpio:
 585         if (gpio_is_valid(eoc_gpio))
 586                 gpio_free(eoc_gpio);
 587 exit:
 588         return err;
 589 }
 590
 591 static int ak8975_remove(struct i2c_client *client)
 592 {
 593         struct iio_dev *indio_dev = i2c_get_clientdata(client);
 594         struct ak8975_data *data = iio_priv(indio_dev);
 595
 596         iio_device_unregister(indio_dev);
 597
 598         if (data->eoc_irq)
 599                 free_irq(data->eoc_irq, data);
 600
 601         if (gpio_is_valid(data->eoc_gpio))
 602                 gpio_free(data->eoc_gpio);
 603
 604         iio_device_free(indio_dev);
 605
 606         return 0;
 607 }
 608
 609 static const struct i2c_device_id ak8975_id[] = {
 610         {"ak8975", AK8975},
 611         {"ak8963", AK8963},
 612         {}
 613 };
 614
 615 MODULE_DEVICE_TABLE(i2c, ak8975_id);
 616
 617 static const struct of_device_id ak8975_of_match[] = {
 618         { .compatible = "asahi-kasei,ak8975", },
 619         { .compatible = "ak8975", },
 620         { }
 621 };
 622 MODULE_DEVICE_TABLE(of, ak8975_of_match);
 623
 624 static struct i2c_driver ak8975_driver = {
 625         .driver = {
 626                 .name   = "ak8975",
 627                 .of_match_table = ak8975_of_match,
 628                 .acpi_match_table = ACPI_PTR(ak_acpi_match),
 629         },
 630         .probe          = ak8975_probe,
 631         .remove         = ak8975_remove,
 632         .id_table       = ak8975_id,
 633 };
 634 module_i2c_driver(ak8975_driver);
 635
 636 MODULE_AUTHOR("Laxman Dewangan <ldewangan@nvidia.com>");
 637 MODULE_DESCRIPTION("AK8975 magnetometer driver");
 638 MODULE_LICENSE("GPL");