drivers/w1/slaves/w1_ds28e17.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  *      w1_ds28e17.c - w1 family 19 (DS28E17) driver
   4  *
   5  * Copyright (c) 2016 Jan Kandziora <jjj@gmx.de>
   6  */
   7
   8 #include <linux/crc16.h>
   9 #include <linux/delay.h>
  10 #include <linux/device.h>
  11 #include <linux/i2c.h>
  12 #include <linux/kernel.h>
  13 #include <linux/module.h>
  14 #include <linux/moduleparam.h>
  15 #include <linux/slab.h>
  16 #include <linux/types.h>
  17 #include <linux/uaccess.h>
  18
  19 #define CRC16_INIT 0
  20
  21 #include <linux/w1.h>
  22
  23 #define W1_FAMILY_DS28E17 0x19
  24
  25 /* Module setup. */
  26 MODULE_LICENSE("GPL v2");
  27 MODULE_AUTHOR("Jan Kandziora <jjj@gmx.de>");
  28 MODULE_DESCRIPTION("w1 family 19 driver for DS28E17, 1-wire to I2C master bridge");
  29 MODULE_ALIAS("w1-family-" __stringify(W1_FAMILY_DS28E17));
  30
  31
  32 /* Default I2C speed to be set when a DS28E17 is detected. */
  33 static int i2c_speed = 100;
  34 module_param_named(speed, i2c_speed, int, (S_IRUSR | S_IWUSR));
  35 MODULE_PARM_DESC(speed, "Default I2C speed to be set when a DS28E17 is detected");
  36
  37 /* Default I2C stretch value to be set when a DS28E17 is detected. */
  38 static char i2c_stretch = 1;
  39 module_param_named(stretch, i2c_stretch, byte, (S_IRUSR | S_IWUSR));
  40 MODULE_PARM_DESC(stretch, "Default I2C stretch value to be set when a DS28E17 is detected");
  41
  42 /* DS28E17 device command codes. */
  43 #define W1_F19_WRITE_DATA_WITH_STOP      0x4B
  44 #define W1_F19_WRITE_DATA_NO_STOP        0x5A
  45 #define W1_F19_WRITE_DATA_ONLY           0x69
  46 #define W1_F19_WRITE_DATA_ONLY_WITH_STOP 0x78
  47 #define W1_F19_READ_DATA_WITH_STOP       0x87
  48 #define W1_F19_WRITE_READ_DATA_WITH_STOP 0x2D
  49 #define W1_F19_WRITE_CONFIGURATION       0xD2
  50 #define W1_F19_READ_CONFIGURATION        0xE1
  51 #define W1_F19_ENABLE_SLEEP_MODE         0x1E
  52 #define W1_F19_READ_DEVICE_REVISION      0xC4
  53
  54 /* DS28E17 status bits */
  55 #define W1_F19_STATUS_CRC     0x01
  56 #define W1_F19_STATUS_ADDRESS 0x02
  57 #define W1_F19_STATUS_START   0x08
  58
  59 /*
  60  * Maximum number of I2C bytes to transfer within one CRC16 protected onewire
  61  * command.
  62  * */
  63 #define W1_F19_WRITE_DATA_LIMIT 255
  64
  65 /* Maximum number of I2C bytes to read with one onewire command. */
  66 #define W1_F19_READ_DATA_LIMIT 255
  67
  68 /* Constants for calculating the busy sleep. */
  69 #define W1_F19_BUSY_TIMEBASES { 90, 23, 10 }
  70 #define W1_F19_BUSY_GRATUITY  1000
  71
  72 /* Number of checks for the busy flag before timeout. */
  73 #define W1_F19_BUSY_CHECKS 1000
  74
  75
  76 /* Slave specific data. */
  77 struct w1_f19_data {
  78         u8 speed;
  79         u8 stretch;
  80         struct i2c_adapter adapter;
  81 };
  82
  83
  84 /* Wait a while until the busy flag clears. */
  85 static int w1_f19_i2c_busy_wait(struct w1_slave *sl, size_t count)
  86 {
  87         const unsigned long timebases[3] = W1_F19_BUSY_TIMEBASES;
  88         struct w1_f19_data *data = sl->family_data;
  89         unsigned int checks;
  90
  91         /* Check the busy flag first in any case.*/
  92         if (w1_touch_bit(sl->master, 1) == 0)
  93                 return 0;
  94
  95         /*
  96          * Do a generously long sleep in the beginning,
  97          * as we have to wait at least this time for all
  98          * the I2C bytes at the given speed to be transferred.
  99          */
 100         usleep_range(timebases[data->speed] * (data->stretch) * count,
 101                 timebases[data->speed] * (data->stretch) * count
 102                 + W1_F19_BUSY_GRATUITY);
 103
 104         /* Now continusly check the busy flag sent by the DS28E17. */
 105         checks = W1_F19_BUSY_CHECKS;
 106         while ((checks--) > 0) {
 107                 /* Return success if the busy flag is cleared. */
 108                 if (w1_touch_bit(sl->master, 1) == 0)
 109                         return 0;
 110
 111                 /* Wait one non-streched byte timeslot. */
 112                 udelay(timebases[data->speed]);
 113         }
 114
 115         /* Timeout. */
 116         dev_warn(&sl->dev, "busy timeout\n");
 117         return -ETIMEDOUT;
 118 }
 119
 120
 121 /* Utility function: result. */
 122 static size_t w1_f19_error(struct w1_slave *sl, u8 w1_buf[])
 123 {
 124         /* Warnings. */
 125         if (w1_buf[0] & W1_F19_STATUS_CRC)
 126                 dev_warn(&sl->dev, "crc16 mismatch\n");
 127         if (w1_buf[0] & W1_F19_STATUS_ADDRESS)
 128                 dev_warn(&sl->dev, "i2c device not responding\n");
 129         if ((w1_buf[0] & (W1_F19_STATUS_CRC | W1_F19_STATUS_ADDRESS)) == 0
 130                         && w1_buf[1] != 0) {
 131                 dev_warn(&sl->dev, "i2c short write, %d bytes not acknowledged\n",
 132                         w1_buf[1]);
 133         }
 134
 135         /* Check error conditions. */
 136         if (w1_buf[0] & W1_F19_STATUS_ADDRESS)
 137                 return -ENXIO;
 138         if (w1_buf[0] & W1_F19_STATUS_START)
 139                 return -EAGAIN;
 140         if (w1_buf[0] != 0 || w1_buf[1] != 0)
 141                 return -EIO;
 142
 143         /* All ok. */
 144         return 0;
 145 }
 146
 147
 148 /* Utility function: write data to I2C slave, single chunk. */
 149 static int __w1_f19_i2c_write(struct w1_slave *sl,
 150         const u8 *command, size_t command_count,
 151         const u8 *buffer, size_t count)
 152 {
 153         u16 crc;
 154         int error;
 155         u8 w1_buf[2];
 156
 157         /* Send command and I2C data to DS28E17. */
 158         crc = crc16(CRC16_INIT, command, command_count);
 159         w1_write_block(sl->master, command, command_count);
 160
 161         w1_buf[0] = count;
 162         crc = crc16(crc, w1_buf, 1);
 163         w1_write_8(sl->master, w1_buf[0]);
 164
 165         crc = crc16(crc, buffer, count);
 166         w1_write_block(sl->master, buffer, count);
 167
 168         w1_buf[0] = ~(crc & 0xFF);
 169         w1_buf[1] = ~((crc >> 8) & 0xFF);
 170         w1_write_block(sl->master, w1_buf, 2);
 171
 172         /* Wait until busy flag clears (or timeout). */
 173         if (w1_f19_i2c_busy_wait(sl, count + 1) < 0)
 174                 return -ETIMEDOUT;
 175
 176         /* Read status from DS28E17. */
 177         w1_read_block(sl->master, w1_buf, 2);
 178
 179         /* Check error conditions. */
 180         error = w1_f19_error(sl, w1_buf);
 181         if (error < 0)
 182                 return error;
 183
 184         /* Return number of bytes written. */
 185         return count;
 186 }
 187
 188
 189 /* Write data to I2C slave. */
 190 static int w1_f19_i2c_write(struct w1_slave *sl, u16 i2c_address,
 191         const u8 *buffer, size_t count, bool stop)
 192 {
 193         int result;
 194         int remaining = count;
 195         const u8 *p;
 196         u8 command[2];
 197
 198         /* Check input. */
 199         if (count == 0)
 200                 return -EOPNOTSUPP;
 201
 202         /* Check whether we need multiple commands. */
 203         if (count <= W1_F19_WRITE_DATA_LIMIT) {
 204                 /*
 205                  * Small data amount. Data can be sent with
 206                  * a single onewire command.
 207                  */
 208
 209                 /* Send all data to DS28E17. */
 210                 command[0] = (stop ? W1_F19_WRITE_DATA_WITH_STOP
 211                         : W1_F19_WRITE_DATA_NO_STOP);
 212                 command[1] = i2c_address << 1;
 213                 result = __w1_f19_i2c_write(sl, command, 2, buffer, count);
 214         } else {
 215                 /* Large data amount. Data has to be sent in multiple chunks. */
 216
 217                 /* Send first chunk to DS28E17. */
 218                 p = buffer;
 219                 command[0] = W1_F19_WRITE_DATA_NO_STOP;
 220                 command[1] = i2c_address << 1;
 221                 result = __w1_f19_i2c_write(sl, command, 2, p,
 222                         W1_F19_WRITE_DATA_LIMIT);
 223                 if (result < 0)
 224                         return result;
 225
 226                 /* Resume to same DS28E17. */
 227                 if (w1_reset_resume_command(sl->master))
 228                         return -EIO;
 229
 230                 /* Next data chunk. */
 231                 p += W1_F19_WRITE_DATA_LIMIT;
 232                 remaining -= W1_F19_WRITE_DATA_LIMIT;
 233
 234                 while (remaining > W1_F19_WRITE_DATA_LIMIT) {
 235                         /* Send intermediate chunk to DS28E17. */
 236                         command[0] = W1_F19_WRITE_DATA_ONLY;
 237                         result = __w1_f19_i2c_write(sl, command, 1, p,
 238                                         W1_F19_WRITE_DATA_LIMIT);
 239                         if (result < 0)
 240                                 return result;
 241
 242                         /* Resume to same DS28E17. */
 243                         if (w1_reset_resume_command(sl->master))
 244                                 return -EIO;
 245
 246                         /* Next data chunk. */
 247                         p += W1_F19_WRITE_DATA_LIMIT;
 248                         remaining -= W1_F19_WRITE_DATA_LIMIT;
 249                 }
 250
 251                 /* Send final chunk to DS28E17. */
 252                 command[0] = (stop ? W1_F19_WRITE_DATA_ONLY_WITH_STOP
 253                         : W1_F19_WRITE_DATA_ONLY);
 254                 result = __w1_f19_i2c_write(sl, command, 1, p, remaining);
 255         }
 256
 257         return result;
 258 }
 259
 260
 261 /* Read data from I2C slave. */
 262 static int w1_f19_i2c_read(struct w1_slave *sl, u16 i2c_address,
 263         u8 *buffer, size_t count)
 264 {
 265         u16 crc;
 266         int error;
 267         u8 w1_buf[5];
 268
 269         /* Check input. */
 270         if (count == 0)
 271                 return -EOPNOTSUPP;
 272
 273         /* Send command to DS28E17. */
 274         w1_buf[0] = W1_F19_READ_DATA_WITH_STOP;
 275         w1_buf[1] = i2c_address << 1 | 0x01;
 276         w1_buf[2] = count;
 277         crc = crc16(CRC16_INIT, w1_buf, 3);
 278         w1_buf[3] = ~(crc & 0xFF);
 279         w1_buf[4] = ~((crc >> 8) & 0xFF);
 280         w1_write_block(sl->master, w1_buf, 5);
 281
 282         /* Wait until busy flag clears (or timeout). */
 283         if (w1_f19_i2c_busy_wait(sl, count + 1) < 0)
 284                 return -ETIMEDOUT;
 285
 286         /* Read status from DS28E17. */
 287         w1_buf[0] = w1_read_8(sl->master);
 288         w1_buf[1] = 0;
 289
 290         /* Check error conditions. */
 291         error = w1_f19_error(sl, w1_buf);
 292         if (error < 0)
 293                 return error;
 294
 295         /* Read received I2C data from DS28E17. */
 296         return w1_read_block(sl->master, buffer, count);
 297 }
 298
 299
 300 /* Write to, then read data from I2C slave. */
 301 static int w1_f19_i2c_write_read(struct w1_slave *sl, u16 i2c_address,
 302         const u8 *wbuffer, size_t wcount, u8 *rbuffer, size_t rcount)
 303 {
 304         u16 crc;
 305         int error;
 306         u8 w1_buf[3];
 307
 308         /* Check input. */
 309         if (wcount == 0 || rcount == 0)
 310                 return -EOPNOTSUPP;
 311
 312         /* Send command and I2C data to DS28E17. */
 313         w1_buf[0] = W1_F19_WRITE_READ_DATA_WITH_STOP;
 314         w1_buf[1] = i2c_address << 1;
 315         w1_buf[2] = wcount;
 316         crc = crc16(CRC16_INIT, w1_buf, 3);
 317         w1_write_block(sl->master, w1_buf, 3);
 318
 319         crc = crc16(crc, wbuffer, wcount);
 320         w1_write_block(sl->master, wbuffer, wcount);
 321
 322         w1_buf[0] = rcount;
 323         crc = crc16(crc, w1_buf, 1);
 324         w1_buf[1] = ~(crc & 0xFF);
 325         w1_buf[2] = ~((crc >> 8) & 0xFF);
 326         w1_write_block(sl->master, w1_buf, 3);
 327
 328         /* Wait until busy flag clears (or timeout). */
 329         if (w1_f19_i2c_busy_wait(sl, wcount + rcount + 2) < 0)
 330                 return -ETIMEDOUT;
 331
 332         /* Read status from DS28E17. */
 333         w1_read_block(sl->master, w1_buf, 2);
 334
 335         /* Check error conditions. */
 336         error = w1_f19_error(sl, w1_buf);
 337         if (error < 0)
 338                 return error;
 339
 340         /* Read received I2C data from DS28E17. */
 341         return w1_read_block(sl->master, rbuffer, rcount);
 342 }
 343
 344
 345 /* Do an I2C master transfer. */
 346 static int w1_f19_i2c_master_transfer(struct i2c_adapter *adapter,
 347         struct i2c_msg *msgs, int num)
 348 {
 349         struct w1_slave *sl = (struct w1_slave *) adapter->algo_data;
 350         int i = 0;
 351         int result = 0;
 352
 353         /* Start onewire transaction. */
 354         mutex_lock(&sl->master->bus_mutex);
 355
 356         /* Select DS28E17. */
 357         if (w1_reset_select_slave(sl)) {
 358                 i = -EIO;
 359                 goto error;
 360         }
 361
 362         /* Loop while there are still messages to transfer. */
 363         while (i < num) {
 364                 /*
 365                  * Check for special case: Small write followed
 366                  * by read to same I2C device.
 367                  */
 368                 if (i < (num-1)
 369                         && msgs[i].addr == msgs[i+1].addr
 370                         && !(msgs[i].flags & I2C_M_RD)
 371                         && (msgs[i+1].flags & I2C_M_RD)
 372                         && (msgs[i].len <= W1_F19_WRITE_DATA_LIMIT)) {
 373                         /*
 374                          * The DS28E17 has a combined transfer
 375                          * for small write+read.
 376                          */
 377                         result = w1_f19_i2c_write_read(sl, msgs[i].addr,
 378                                 msgs[i].buf, msgs[i].len,
 379                                 msgs[i+1].buf, msgs[i+1].len);
 380                         if (result < 0) {
 381                                 i = result;
 382                                 goto error;
 383                         }
 384
 385                         /*
 386                          * Check if we should interpret the read data
 387                          * as a length byte. The DS28E17 unfortunately
 388                          * has no read without stop, so we can just do
 389                          * another simple read in that case.
 390                          */
 391                         if (msgs[i+1].flags & I2C_M_RECV_LEN) {
 392                                 result = w1_f19_i2c_read(sl, msgs[i+1].addr,
 393                                         &(msgs[i+1].buf[1]), msgs[i+1].buf[0]);
 394                                 if (result < 0) {
 395                                         i = result;
 396                                         goto error;
 397                                 }
 398                         }
 399
 400                         /* Eat up read message, too. */
 401                         i++;
 402                 } else if (msgs[i].flags & I2C_M_RD) {
 403                         /* Read transfer. */
 404                         result = w1_f19_i2c_read(sl, msgs[i].addr,
 405                                 msgs[i].buf, msgs[i].len);
 406                         if (result < 0) {
 407                                 i = result;
 408                                 goto error;
 409                         }
 410
 411                         /*
 412                          * Check if we should interpret the read data
 413                          * as a length byte. The DS28E17 unfortunately
 414                          * has no read without stop, so we can just do
 415                          * another simple read in that case.
 416                          */
 417                         if (msgs[i].flags & I2C_M_RECV_LEN) {
 418                                 result = w1_f19_i2c_read(sl,
 419                                         msgs[i].addr,
 420                                         &(msgs[i].buf[1]),
 421                                         msgs[i].buf[0]);
 422                                 if (result < 0) {
 423                                         i = result;
 424                                         goto error;
 425                                 }
 426                         }
 427                 } else {
 428                         /*
 429                          * Write transfer.
 430                          * Stop condition only for last
 431                          * transfer.
 432                          */
 433                         result = w1_f19_i2c_write(sl,
 434                                 msgs[i].addr,
 435                                 msgs[i].buf,
 436                                 msgs[i].len,
 437                                 i == (num-1));
 438                         if (result < 0) {
 439                                 i = result;
 440                                 goto error;
 441                         }
 442                 }
 443
 444                 /* Next message. */
 445                 i++;
 446
 447                 /* Are there still messages to send/receive? */
 448                 if (i < num) {
 449                         /* Yes. Resume to same DS28E17. */
 450                         if (w1_reset_resume_command(sl->master)) {
 451                                 i = -EIO;
 452                                 goto error;
 453                         }
 454                 }
 455         }
 456
 457 error:
 458         /* End onewire transaction. */
 459         mutex_unlock(&sl->master->bus_mutex);
 460
 461         /* Return number of messages processed or error. */
 462         return i;
 463 }
 464
 465
 466 /* Get I2C adapter functionality. */
 467 static u32 w1_f19_i2c_functionality(struct i2c_adapter *adapter)
 468 {
 469         /*
 470          * Plain I2C functions only.
 471          * SMBus is emulated by the kernel's I2C layer.
 472          * No "I2C_FUNC_SMBUS_QUICK"
 473          * No "I2C_FUNC_SMBUS_READ_BLOCK_DATA"
 474          * No "I2C_FUNC_SMBUS_BLOCK_PROC_CALL"
 475          */
 476         return I2C_FUNC_I2C |
 477                 I2C_FUNC_SMBUS_BYTE |
 478                 I2C_FUNC_SMBUS_BYTE_DATA |
 479                 I2C_FUNC_SMBUS_WORD_DATA |
 480                 I2C_FUNC_SMBUS_PROC_CALL |
 481                 I2C_FUNC_SMBUS_WRITE_BLOCK_DATA |
 482                 I2C_FUNC_SMBUS_I2C_BLOCK |
 483                 I2C_FUNC_SMBUS_PEC;
 484 }
 485
 486
 487 /* I2C adapter quirks. */
 488 static const struct i2c_adapter_quirks w1_f19_i2c_adapter_quirks = {
 489         .max_read_len = W1_F19_READ_DATA_LIMIT,
 490 };
 491
 492 /* I2C algorithm. */
 493 static const struct i2c_algorithm w1_f19_i2c_algorithm = {
 494         .master_xfer    = w1_f19_i2c_master_transfer,
 495         .functionality  = w1_f19_i2c_functionality,
 496 };
 497
 498
 499 /* Read I2C speed from DS28E17. */
 500 static int w1_f19_get_i2c_speed(struct w1_slave *sl)
 501 {
 502         struct w1_f19_data *data = sl->family_data;
 503         int result = -EIO;
 504
 505         /* Start onewire transaction. */
 506         mutex_lock(&sl->master->bus_mutex);
 507
 508         /* Select slave. */
 509         if (w1_reset_select_slave(sl))
 510                 goto error;
 511
 512         /* Read slave configuration byte. */
 513         w1_write_8(sl->master, W1_F19_READ_CONFIGURATION);
 514         result = w1_read_8(sl->master);
 515         if (result < 0 || result > 2) {
 516                 result = -EIO;
 517                 goto error;
 518         }
 519
 520         /* Update speed in slave specific data. */
 521         data->speed = result;
 522
 523 error:
 524         /* End onewire transaction. */
 525         mutex_unlock(&sl->master->bus_mutex);
 526
 527         return result;
 528 }
 529
 530
 531 /* Set I2C speed on DS28E17. */
 532 static int __w1_f19_set_i2c_speed(struct w1_slave *sl, u8 speed)
 533 {
 534         struct w1_f19_data *data = sl->family_data;
 535         const int i2c_speeds[3] = { 100, 400, 900 };
 536         u8 w1_buf[2];
 537
 538         /* Select slave. */
 539         if (w1_reset_select_slave(sl))
 540                 return -EIO;
 541
 542         w1_buf[0] = W1_F19_WRITE_CONFIGURATION;
 543         w1_buf[1] = speed;
 544         w1_write_block(sl->master, w1_buf, 2);
 545
 546         /* Update speed in slave specific data. */
 547         data->speed = speed;
 548
 549         dev_info(&sl->dev, "i2c speed set to %d kBaud\n", i2c_speeds[speed]);
 550
 551         return 0;
 552 }
 553
 554 static int w1_f19_set_i2c_speed(struct w1_slave *sl, u8 speed)
 555 {
 556         int result;
 557
 558         /* Start onewire transaction. */
 559         mutex_lock(&sl->master->bus_mutex);
 560
 561         /* Set I2C speed on DS28E17. */
 562         result = __w1_f19_set_i2c_speed(sl, speed);
 563
 564         /* End onewire transaction. */
 565         mutex_unlock(&sl->master->bus_mutex);
 566
 567         return result;
 568 }
 569
 570
 571 /* Sysfs attributes. */
 572
 573 /* I2C speed attribute for a single chip. */
 574 static ssize_t speed_show(struct device *dev, struct device_attribute *attr,
 575                              char *buf)
 576 {
 577         struct w1_slave *sl = dev_to_w1_slave(dev);
 578         int result;
 579
 580         /* Read current speed from slave. Updates data->speed. */
 581         result = w1_f19_get_i2c_speed(sl);
 582         if (result < 0)
 583                 return result;
 584
 585         /* Return current speed value. */
 586         return sprintf(buf, "%d\n", result);
 587 }
 588
 589 static ssize_t speed_store(struct device *dev, struct device_attribute *attr,
 590                               const char *buf, size_t count)
 591 {
 592         struct w1_slave *sl = dev_to_w1_slave(dev);
 593         int error;
 594
 595         /* Valid values are: "100", "400", "900" */
 596         if (count < 3 || count > 4 || !buf)
 597                 return -EINVAL;
 598         if (count == 4 && buf[3] != '\n')
 599                 return -EINVAL;
 600         if (buf[1] != '0' || buf[2] != '0')
 601                 return -EINVAL;
 602
 603         /* Set speed on slave. */
 604         switch (buf[0]) {
 605         case '1':
 606                 error = w1_f19_set_i2c_speed(sl, 0);
 607                 break;
 608         case '4':
 609                 error = w1_f19_set_i2c_speed(sl, 1);
 610                 break;
 611         case '9':
 612                 error = w1_f19_set_i2c_speed(sl, 2);
 613                 break;
 614         default:
 615                 return -EINVAL;
 616         }
 617
 618         if (error < 0)
 619                 return error;
 620
 621         /* Return bytes written. */
 622         return count;
 623 }
 624
 625 static DEVICE_ATTR_RW(speed);
 626
 627
 628 /* Busy stretch attribute for a single chip. */
 629 static ssize_t stretch_show(struct device *dev, struct device_attribute *attr,
 630                              char *buf)
 631 {
 632         struct w1_slave *sl = dev_to_w1_slave(dev);
 633         struct w1_f19_data *data = sl->family_data;
 634
 635         /* Return current stretch value. */
 636         return sprintf(buf, "%d\n", data->stretch);
 637 }
 638
 639 static ssize_t stretch_store(struct device *dev, struct device_attribute *attr,
 640                               const char *buf, size_t count)
 641 {
 642         struct w1_slave *sl = dev_to_w1_slave(dev);
 643         struct w1_f19_data *data = sl->family_data;
 644
 645         /* Valid values are '1' to '9' */
 646         if (count < 1 || count > 2 || !buf)
 647                 return -EINVAL;
 648         if (count == 2 && buf[1] != '\n')
 649                 return -EINVAL;
 650         if (buf[0] < '1' || buf[0] > '9')
 651                 return -EINVAL;
 652
 653         /* Set busy stretch value. */
 654         data->stretch = buf[0] & 0x0F;
 655
 656         /* Return bytes written. */
 657         return count;
 658 }
 659
 660 static DEVICE_ATTR_RW(stretch);
 661
 662
 663 /* All attributes. */
 664 static struct attribute *w1_f19_attrs[] = {
 665         &dev_attr_speed.attr,
 666         &dev_attr_stretch.attr,
 667         NULL,
 668 };
 669
 670 static const struct attribute_group w1_f19_group = {
 671         .attrs          = w1_f19_attrs,
 672 };
 673
 674 static const struct attribute_group *w1_f19_groups[] = {
 675         &w1_f19_group,
 676         NULL,
 677 };
 678
 679
 680 /* Slave add and remove functions. */
 681 static int w1_f19_add_slave(struct w1_slave *sl)
 682 {
 683         struct w1_f19_data *data = NULL;
 684
 685         /* Allocate memory for slave specific data. */
 686         data = devm_kzalloc(&sl->dev, sizeof(*data), GFP_KERNEL);
 687         if (!data)
 688                 return -ENOMEM;
 689         sl->family_data = data;
 690
 691         /* Setup default I2C speed on slave. */
 692         switch (i2c_speed) {
 693         case 100:
 694                 __w1_f19_set_i2c_speed(sl, 0);
 695                 break;
 696         case 400:
 697                 __w1_f19_set_i2c_speed(sl, 1);
 698                 break;
 699         case 900:
 700                 __w1_f19_set_i2c_speed(sl, 2);
 701                 break;
 702         default:
 703                 /*
 704                  * A i2c_speed module parameter of anything else
 705                  * than 100, 400, 900 means not to touch the
 706                  * speed of the DS28E17.
 707                  * We assume 400kBaud, the power-on value.
 708                  */
 709                 data->speed = 1;
 710         }
 711
 712         /*
 713          * Setup default busy stretch
 714          * configuration for the DS28E17.
 715          */
 716         data->stretch = i2c_stretch;
 717
 718         /* Setup I2C adapter. */
 719         data->adapter.owner      = THIS_MODULE;
 720         data->adapter.algo       = &w1_f19_i2c_algorithm;
 721         data->adapter.algo_data  = sl;
 722         strcpy(data->adapter.name, "w1-");
 723         strcat(data->adapter.name, sl->name);
 724         data->adapter.dev.parent = &sl->dev;
 725         data->adapter.quirks     = &w1_f19_i2c_adapter_quirks;
 726
 727         return i2c_add_adapter(&data->adapter);
 728 }
 729
 730 static void w1_f19_remove_slave(struct w1_slave *sl)
 731 {
 732         struct w1_f19_data *family_data = sl->family_data;
 733
 734         /* Delete I2C adapter. */
 735         i2c_del_adapter(&family_data->adapter);
 736
 737         /* Free slave specific data. */
 738         devm_kfree(&sl->dev, family_data);
 739         sl->family_data = NULL;
 740 }
 741
 742
 743 /* Declarations within the w1 subsystem. */
 744 static const struct w1_family_ops w1_f19_fops = {
 745         .add_slave = w1_f19_add_slave,
 746         .remove_slave = w1_f19_remove_slave,
 747         .groups = w1_f19_groups,
 748 };
 749
 750 static struct w1_family w1_family_19 = {
 751         .fid = W1_FAMILY_DS28E17,
 752         .fops = &w1_f19_fops,
 753 };
 754
 755
 756 /* Module init and remove functions. */
 757 static int __init w1_f19_init(void)
 758 {
 759         return w1_register_family(&w1_family_19);
 760 }
 761
 762 static void __exit w1_f19_fini(void)
 763 {
 764         w1_unregister_family(&w1_family_19);
 765 }
 766
 767 module_init(w1_f19_init);
 768 module_exit(w1_f19_fini);
 769