Documentation/hwmon/sysfs-interface

   1 Naming and data format standards for sysfs files
   2 ================================================
   3
   4 The libsensors library offers an interface to the raw sensors data
   5 through the sysfs interface. Since lm-sensors 3.0.0, libsensors is
   6 completely chip-independent. It assumes that all the kernel drivers
   7 implement the standard sysfs interface described in this document.
   8 This makes adding or updating support for any given chip very easy, as
   9 libsensors, and applications using it, do not need to be modified.
  10 This is a major improvement compared to lm-sensors 2.
  11
  12 Note that motherboards vary widely in the connections to sensor chips.
  13 There is no standard that ensures, for example, that the second
  14 temperature sensor is connected to the CPU, or that the second fan is on
  15 the CPU. Also, some values reported by the chips need some computation
  16 before they make full sense. For example, most chips can only measure
  17 voltages between 0 and +4V. Other voltages are scaled back into that
  18 range using external resistors. Since the values of these resistors
  19 can change from motherboard to motherboard, the conversions cannot be
  20 hard coded into the driver and have to be done in user space.
  21
  22 For this reason, even if we aim at a chip-independent libsensors, it will
  23 still require a configuration file (e.g. /etc/sensors.conf) for proper
  24 values conversion, labeling of inputs and hiding of unused inputs.
  25
  26 An alternative method that some programs use is to access the sysfs
  27 files directly. This document briefly describes the standards that the
  28 drivers follow, so that an application program can scan for entries and
  29 access this data in a simple and consistent way. That said, such programs
  30 will have to implement conversion, labeling and hiding of inputs. For
  31 this reason, it is still not recommended to bypass the library.
  32
  33 Each chip gets its own directory in the sysfs /sys/devices tree.  To
  34 find all sensor chips, it is easier to follow the device symlinks from
  35 `/sys/class/hwmon/hwmon*`.
  36
  37 Up to lm-sensors 3.0.0, libsensors looks for hardware monitoring attributes
  38 in the "physical" device directory. Since lm-sensors 3.0.1, attributes found
  39 in the hwmon "class" device directory are also supported. Complex drivers
  40 (e.g. drivers for multifunction chips) may want to use this possibility to
  41 avoid namespace pollution. The only drawback will be that older versions of
  42 libsensors won't support the driver in question.
  43
  44 All sysfs values are fixed point numbers.
  45
  46 There is only one value per file, unlike the older /proc specification.
  47 The common scheme for files naming is: <type><number>_<item>. Usual
  48 types for sensor chips are "in" (voltage), "temp" (temperature) and
  49 "fan" (fan). Usual items are "input" (measured value), "max" (high
  50 threshold, "min" (low threshold). Numbering usually starts from 1,
  51 except for voltages which start from 0 (because most data sheets use
  52 this). A number is always used for elements that can be present more
  53 than once, even if there is a single element of the given type on the
  54 specific chip. Other files do not refer to a specific element, so
  55 they have a simple name, and no number.
  56
  57 Alarms are direct indications read from the chips. The drivers do NOT
  58 make comparisons of readings to thresholds. This allows violations
  59 between readings to be caught and alarmed. The exact definition of an
  60 alarm (for example, whether a threshold must be met or must be exceeded
  61 to cause an alarm) is chip-dependent.
  62
  63 When setting values of hwmon sysfs attributes, the string representation of
  64 the desired value must be written, note that strings which are not a number
  65 are interpreted as 0! For more on how written strings are interpreted see the
  66 "sysfs attribute writes interpretation" section at the end of this file.
  67
  68 -------------------------------------------------------------------------
  69
  70 ======= ===========================================
  71 `[0-*]` denotes any positive number starting from 0
  72 `[1-*]` denotes any positive number starting from 1
  73 RO      read only value
  74 WO      write only value
  75 RW      read/write value
  76 ======= ===========================================
  77
  78 Read/write values may be read-only for some chips, depending on the
  79 hardware implementation.
  80
  81 All entries (except name) are optional, and should only be created in a
  82 given driver if the chip has the feature.
  83
  84
  85 *****************
  86 Global attributes
  87 *****************
  88
  89 `name`
  90                 The chip name.
  91                 This should be a short, lowercase string, not containing
  92                 whitespace, dashes, or the wildcard character '*'.
  93                 This attribute represents the chip name. It is the only
  94                 mandatory attribute.
  95                 I2C devices get this attribute created automatically.
  96
  97                 RO
  98
  99 `update_interval`
 100                 The interval at which the chip will update readings.
 101                 Unit: millisecond
 102
 103                 RW
 104
 105                 Some devices have a variable update rate or interval.
 106                 This attribute can be used to change it to the desired value.
 107
 108
 109 ********
 110 Voltages
 111 ********
 112
 113 `in[0-*]_min`
 114                 Voltage min value.
 115
 116                 Unit: millivolt
 117
 118                 RW
 119
 120 `in[0-*]_lcrit`
 121                 Voltage critical min value.
 122
 123                 Unit: millivolt
 124
 125                 RW
 126
 127                 If voltage drops to or below this limit, the system may
 128                 take drastic action such as power down or reset. At the very
 129                 least, it should report a fault.
 130
 131 `in[0-*]_max`
 132                 Voltage max value.
 133
 134                 Unit: millivolt
 135
 136                 RW
 137
 138 `in[0-*]_crit`
 139                 Voltage critical max value.
 140
 141                 Unit: millivolt
 142
 143                 RW
 144
 145                 If voltage reaches or exceeds this limit, the system may
 146                 take drastic action such as power down or reset. At the very
 147                 least, it should report a fault.
 148
 149 `in[0-*]_input`
 150                 Voltage input value.
 151
 152                 Unit: millivolt
 153
 154                 RO
 155
 156                 Voltage measured on the chip pin.
 157
 158                 Actual voltage depends on the scaling resistors on the
 159                 motherboard, as recommended in the chip datasheet.
 160
 161                 This varies by chip and by motherboard.
 162                 Because of this variation, values are generally NOT scaled
 163                 by the chip driver, and must be done by the application.
 164                 However, some drivers (notably lm87 and via686a)
 165                 do scale, because of internal resistors built into a chip.
 166                 These drivers will output the actual voltage. Rule of
 167                 thumb: drivers should report the voltage values at the
 168                 "pins" of the chip.
 169
 170 `in[0-*]_average`
 171                 Average voltage
 172
 173                 Unit: millivolt
 174
 175                 RO
 176
 177 `in[0-*]_lowest`
 178                 Historical minimum voltage
 179
 180                 Unit: millivolt
 181
 182                 RO
 183
 184 `in[0-*]_highest`
 185                 Historical maximum voltage
 186
 187                 Unit: millivolt
 188
 189                 RO
 190
 191 `in[0-*]_reset_history`
 192                 Reset inX_lowest and inX_highest
 193
 194                 WO
 195
 196 `in_reset_history`
 197                 Reset inX_lowest and inX_highest for all sensors
 198
 199                 WO
 200
 201 `in[0-*]_label`
 202                 Suggested voltage channel label.
 203
 204                 Text string
 205
 206                 Should only be created if the driver has hints about what
 207                 this voltage channel is being used for, and user-space
 208                 doesn't. In all other cases, the label is provided by
 209                 user-space.
 210
 211                 RO
 212
 213 `in[0-*]_enable`
 214                 Enable or disable the sensors.
 215
 216                 When disabled the sensor read will return -ENODATA.
 217
 218                 - 1: Enable
 219                 - 0: Disable
 220
 221                 RW
 222
 223 `cpu[0-*]_vid`
 224                 CPU core reference voltage.
 225
 226                 Unit: millivolt
 227
 228                 RO
 229
 230                 Not always correct.
 231
 232 `vrm`
 233                 Voltage Regulator Module version number.
 234
 235                 RW (but changing it should no more be necessary)
 236
 237                 Originally the VRM standard version multiplied by 10, but now
 238                 an arbitrary number, as not all standards have a version
 239                 number.
 240
 241                 Affects the way the driver calculates the CPU core reference
 242                 voltage from the vid pins.
 243
 244 Also see the Alarms section for status flags associated with voltages.
 245
 246
 247 ****
 248 Fans
 249 ****
 250
 251 `fan[1-*]_min`
 252                 Fan minimum value
 253
 254                 Unit: revolution/min (RPM)
 255
 256                 RW
 257
 258 `fan[1-*]_max`
 259                 Fan maximum value
 260
 261                 Unit: revolution/min (RPM)
 262
 263                 Only rarely supported by the hardware.
 264                 RW
 265
 266 `fan[1-*]_input`
 267                 Fan input value.
 268
 269                 Unit: revolution/min (RPM)
 270
 271                 RO
 272
 273 `fan[1-*]_div`
 274                 Fan divisor.
 275
 276                 Integer value in powers of two (1, 2, 4, 8, 16, 32, 64, 128).
 277
 278                 RW
 279
 280                 Some chips only support values 1, 2, 4 and 8.
 281                 Note that this is actually an internal clock divisor, which
 282                 affects the measurable speed range, not the read value.
 283
 284 `fan[1-*]_pulses`
 285                 Number of tachometer pulses per fan revolution.
 286
 287                 Integer value, typically between 1 and 4.
 288
 289                 RW
 290
 291                 This value is a characteristic of the fan connected to the
 292                 device's input, so it has to be set in accordance with the fan
 293                 model.
 294
 295                 Should only be created if the chip has a register to configure
 296                 the number of pulses. In the absence of such a register (and
 297                 thus attribute) the value assumed by all devices is 2 pulses
 298                 per fan revolution.
 299
 300 `fan[1-*]_target`
 301                 Desired fan speed
 302
 303                 Unit: revolution/min (RPM)
 304
 305                 RW
 306
 307                 Only makes sense if the chip supports closed-loop fan speed
 308                 control based on the measured fan speed.
 309
 310 `fan[1-*]_label`
 311                 Suggested fan channel label.
 312
 313                 Text string
 314
 315                 Should only be created if the driver has hints about what
 316                 this fan channel is being used for, and user-space doesn't.
 317                 In all other cases, the label is provided by user-space.
 318
 319                 RO
 320
 321 `fan[1-*]_enable`
 322                 Enable or disable the sensors.
 323
 324                 When disabled the sensor read will return -ENODATA.
 325
 326                 - 1: Enable
 327                 - 0: Disable
 328
 329                 RW
 330
 331 Also see the Alarms section for status flags associated with fans.
 332
 333
 334 ***
 335 PWM
 336 ***
 337
 338 `pwm[1-*]`
 339                 Pulse width modulation fan control.
 340
 341                 Integer value in the range 0 to 255
 342
 343                 RW
 344
 345                 255 is max or 100%.
 346
 347 `pwm[1-*]_enable`
 348                 Fan speed control method:
 349
 350                 - 0: no fan speed control (i.e. fan at full speed)
 351                 - 1: manual fan speed control enabled (using `pwm[1-*]`)
 352                 - 2+: automatic fan speed control enabled
 353
 354                 Check individual chip documentation files for automatic mode
 355                 details.
 356
 357                 RW
 358
 359 `pwm[1-*]_mode`
 360                 - 0: DC mode (direct current)
 361                 - 1: PWM mode (pulse-width modulation)
 362
 363                 RW
 364
 365 `pwm[1-*]_freq`
 366                 Base PWM frequency in Hz.
 367
 368                 Only possibly available when pwmN_mode is PWM, but not always
 369                 present even then.
 370
 371                 RW
 372
 373 `pwm[1-*]_auto_channels_temp`
 374                 Select which temperature channels affect this PWM output in
 375                 auto mode.
 376
 377                 Bitfield, 1 is temp1, 2 is temp2, 4 is temp3 etc...
 378                 Which values are possible depend on the chip used.
 379
 380                 RW
 381
 382 `pwm[1-*]_auto_point[1-*]_pwm` / `pwm[1-*]_auto_point[1-*]_temp` / `pwm[1-*]_auto_point[1-*]_temp_hyst`
 383                 Define the PWM vs temperature curve.
 384
 385                 Number of trip points is chip-dependent. Use this for chips
 386                 which associate trip points to PWM output channels.
 387
 388                 RW
 389
 390 `temp[1-*]_auto_point[1-*]_pwm` / `temp[1-*]_auto_point[1-*]_temp` / `temp[1-*]_auto_point[1-*]_temp_hyst`
 391                 Define the PWM vs temperature curve.
 392
 393                 Number of trip points is chip-dependent. Use this for chips
 394                 which associate trip points to temperature channels.
 395
 396                 RW
 397
 398 There is a third case where trip points are associated to both PWM output
 399 channels and temperature channels: the PWM values are associated to PWM
 400 output channels while the temperature values are associated to temperature
 401 channels. In that case, the result is determined by the mapping between
 402 temperature inputs and PWM outputs. When several temperature inputs are
 403 mapped to a given PWM output, this leads to several candidate PWM values.
 404 The actual result is up to the chip, but in general the highest candidate
 405 value (fastest fan speed) wins.
 406
 407
 408 ************
 409 Temperatures
 410 ************
 411
 412 `temp[1-*]_type`
 413                 Sensor type selection.
 414
 415                 Integers 1 to 6
 416
 417                 RW
 418
 419                 - 1: CPU embedded diode
 420                 - 2: 3904 transistor
 421                 - 3: thermal diode
 422                 - 4: thermistor
 423                 - 5: AMD AMDSI
 424                 - 6: Intel PECI
 425
 426                 Not all types are supported by all chips
 427
 428 `temp[1-*]_max`
 429                 Temperature max value.
 430
 431                 Unit: millidegree Celsius (or millivolt, see below)
 432
 433                 RW
 434
 435 `temp[1-*]_min`
 436                 Temperature min value.
 437
 438                 Unit: millidegree Celsius
 439
 440                 RW
 441
 442 `temp[1-*]_max_hyst`
 443                 Temperature hysteresis value for max limit.
 444
 445                 Unit: millidegree Celsius
 446
 447                 Must be reported as an absolute temperature, NOT a delta
 448                 from the max value.
 449
 450                 RW
 451
 452 `temp[1-*]_min_hyst`
 453                 Temperature hysteresis value for min limit.
 454                 Unit: millidegree Celsius
 455
 456                 Must be reported as an absolute temperature, NOT a delta
 457                 from the min value.
 458
 459                 RW
 460
 461 `temp[1-*]_input`
 462          Temperature input value.
 463
 464                 Unit: millidegree Celsius
 465
 466                 RO
 467
 468 `temp[1-*]_crit`
 469                 Temperature critical max value, typically greater than
 470                 corresponding temp_max values.
 471
 472                 Unit: millidegree Celsius
 473
 474                 RW
 475
 476 `temp[1-*]_crit_hyst`
 477                 Temperature hysteresis value for critical limit.
 478
 479                 Unit: millidegree Celsius
 480
 481                 Must be reported as an absolute temperature, NOT a delta
 482                 from the critical value.
 483
 484                 RW
 485
 486 `temp[1-*]_emergency`
 487                 Temperature emergency max value, for chips supporting more than
 488                 two upper temperature limits. Must be equal or greater than
 489                 corresponding temp_crit values.
 490
 491                 Unit: millidegree Celsius
 492
 493                 RW
 494
 495 `temp[1-*]_emergency_hyst`
 496                 Temperature hysteresis value for emergency limit.
 497
 498                 Unit: millidegree Celsius
 499
 500                 Must be reported as an absolute temperature, NOT a delta
 501                 from the emergency value.
 502
 503                 RW
 504
 505 `temp[1-*]_lcrit`
 506                 Temperature critical min value, typically lower than
 507                 corresponding temp_min values.
 508
 509                 Unit: millidegree Celsius
 510
 511                 RW
 512
 513 `temp[1-*]_lcrit_hyst`
 514                 Temperature hysteresis value for critical min limit.
 515
 516                 Unit: millidegree Celsius
 517
 518                 Must be reported as an absolute temperature, NOT a delta
 519                 from the critical min value.
 520
 521                 RW
 522
 523 `temp[1-*]_offset`
 524                 Temperature offset which is added to the temperature reading
 525                 by the chip.
 526
 527                 Unit: millidegree Celsius
 528
 529                 Read/Write value.
 530
 531 `temp[1-*]_label`
 532                 Suggested temperature channel label.
 533
 534                 Text string
 535
 536                 Should only be created if the driver has hints about what
 537                 this temperature channel is being used for, and user-space
 538                 doesn't. In all other cases, the label is provided by
 539                 user-space.
 540
 541                 RO
 542
 543 `temp[1-*]_lowest`
 544                 Historical minimum temperature
 545
 546                 Unit: millidegree Celsius
 547
 548                 RO
 549
 550 `temp[1-*]_highest`
 551                 Historical maximum temperature
 552
 553                 Unit: millidegree Celsius
 554
 555                 RO
 556
 557 `temp[1-*]_reset_history`
 558                 Reset temp_lowest and temp_highest
 559
 560                 WO
 561
 562 `temp_reset_history`
 563                 Reset temp_lowest and temp_highest for all sensors
 564
 565                 WO
 566
 567 `temp[1-*]_enable`
 568                 Enable or disable the sensors.
 569
 570                 When disabled the sensor read will return -ENODATA.
 571
 572                 - 1: Enable
 573                 - 0: Disable
 574
 575                 RW
 576
 577 Some chips measure temperature using external thermistors and an ADC, and
 578 report the temperature measurement as a voltage. Converting this voltage
 579 back to a temperature (or the other way around for limits) requires
 580 mathematical functions not available in the kernel, so the conversion
 581 must occur in user space. For these chips, all temp* files described
 582 above should contain values expressed in millivolt instead of millidegree
 583 Celsius. In other words, such temperature channels are handled as voltage
 584 channels by the driver.
 585
 586 Also see the Alarms section for status flags associated with temperatures.
 587
 588
 589 ********
 590 Currents
 591 ********
 592
 593 `curr[1-*]_max`
 594                 Current max value
 595
 596                 Unit: milliampere
 597
 598                 RW
 599
 600 `curr[1-*]_min`
 601                 Current min value.
 602
 603                 Unit: milliampere
 604
 605                 RW
 606
 607 `curr[1-*]_lcrit`
 608                 Current critical low value
 609
 610                 Unit: milliampere
 611
 612                 RW
 613
 614 `curr[1-*]_crit`
 615                 Current critical high value.
 616
 617                 Unit: milliampere
 618
 619                 RW
 620
 621 `curr[1-*]_input`
 622                 Current input value
 623
 624                 Unit: milliampere
 625
 626                 RO
 627
 628 `curr[1-*]_average`
 629                 Average current use
 630
 631                 Unit: milliampere
 632
 633                 RO
 634
 635 `curr[1-*]_lowest`
 636                 Historical minimum current
 637
 638                 Unit: milliampere
 639
 640                 RO
 641
 642 `curr[1-*]_highest`
 643                 Historical maximum current
 644                 Unit: milliampere
 645                 RO
 646
 647 `curr[1-*]_reset_history`
 648                 Reset currX_lowest and currX_highest
 649
 650                 WO
 651
 652 `curr_reset_history`
 653                 Reset currX_lowest and currX_highest for all sensors
 654
 655                 WO
 656
 657 `curr[1-*]_enable`
 658                 Enable or disable the sensors.
 659
 660                 When disabled the sensor read will return -ENODATA.
 661
 662                 - 1: Enable
 663                 - 0: Disable
 664
 665                 RW
 666
 667 Also see the Alarms section for status flags associated with currents.
 668
 669 *****
 670 Power
 671 *****
 672
 673 `power[1-*]_average`
 674                                 Average power use
 675
 676                                 Unit: microWatt
 677
 678                                 RO
 679
 680 `power[1-*]_average_interval`
 681                                 Power use averaging interval.  A poll
 682                                 notification is sent to this file if the
 683                                 hardware changes the averaging interval.
 684
 685                                 Unit: milliseconds
 686
 687                                 RW
 688
 689 `power[1-*]_average_interval_max`
 690                                 Maximum power use averaging interval
 691
 692                                 Unit: milliseconds
 693
 694                                 RO
 695
 696 `power[1-*]_average_interval_min`
 697                                 Minimum power use averaging interval
 698
 699                                 Unit: milliseconds
 700
 701                                 RO
 702
 703 `power[1-*]_average_highest`
 704                                 Historical average maximum power use
 705
 706                                 Unit: microWatt
 707
 708                                 RO
 709
 710 `power[1-*]_average_lowest`
 711                                 Historical average minimum power use
 712
 713                                 Unit: microWatt
 714
 715                                 RO
 716
 717 `power[1-*]_average_max`
 718                                 A poll notification is sent to
 719                                 `power[1-*]_average` when power use
 720                                 rises above this value.
 721
 722                                 Unit: microWatt
 723
 724                                 RW
 725
 726 `power[1-*]_average_min`
 727                                 A poll notification is sent to
 728                                 `power[1-*]_average` when power use
 729                                 sinks below this value.
 730
 731                                 Unit: microWatt
 732
 733                                 RW
 734
 735 `power[1-*]_input`
 736                                 Instantaneous power use
 737
 738                                 Unit: microWatt
 739
 740                                 RO
 741
 742 `power[1-*]_input_highest`
 743                                 Historical maximum power use
 744
 745                                 Unit: microWatt
 746
 747                                 RO
 748
 749 `power[1-*]_input_lowest`
 750                                 Historical minimum power use
 751
 752                                 Unit: microWatt
 753
 754                                 RO
 755
 756 `power[1-*]_reset_history`
 757                                 Reset input_highest, input_lowest,
 758                                 average_highest and average_lowest.
 759
 760                                 WO
 761
 762 `power[1-*]_accuracy`
 763                                 Accuracy of the power meter.
 764
 765                                 Unit: Percent
 766
 767                                 RO
 768
 769 `power[1-*]_cap`
 770                                 If power use rises above this limit, the
 771                                 system should take action to reduce power use.
 772                                 A poll notification is sent to this file if the
 773                                 cap is changed by the hardware.  The `*_cap`
 774                                 files only appear if the cap is known to be
 775                                 enforced by hardware.
 776
 777                                 Unit: microWatt
 778
 779                                 RW
 780
 781 `power[1-*]_cap_hyst`
 782                                 Margin of hysteresis built around capping and
 783                                 notification.
 784
 785                                 Unit: microWatt
 786
 787                                 RW
 788
 789 `power[1-*]_cap_max`
 790                                 Maximum cap that can be set.
 791
 792                                 Unit: microWatt
 793
 794                                 RO
 795
 796 `power[1-*]_cap_min`
 797                                 Minimum cap that can be set.
 798
 799                                 Unit: microWatt
 800
 801                                 RO
 802
 803 `power[1-*]_max`
 804                                 Maximum power.
 805
 806                                 Unit: microWatt
 807
 808                                 RW
 809
 810 `power[1-*]_crit`
 811                                 Critical maximum power.
 812
 813                                 If power rises to or above this limit, the
 814                                 system is expected take drastic action to reduce
 815                                 power consumption, such as a system shutdown or
 816                                 a forced powerdown of some devices.
 817
 818                                 Unit: microWatt
 819
 820                                 RW
 821
 822 `power[1-*]_enable`
 823                                 Enable or disable the sensors.
 824
 825                                 When disabled the sensor read will return
 826                                 -ENODATA.
 827
 828                                 - 1: Enable
 829                                 - 0: Disable
 830
 831                                 RW
 832
 833 Also see the Alarms section for status flags associated with power readings.
 834
 835 ******
 836 Energy
 837 ******
 838
 839 `energy[1-*]_input`
 840                                 Cumulative energy use
 841
 842                                 Unit: microJoule
 843
 844                                 RO
 845
 846 `energy[1-*]_enable`
 847                                 Enable or disable the sensors.
 848
 849                                 When disabled the sensor read will return
 850                                 -ENODATA.
 851
 852                                 - 1: Enable
 853                                 - 0: Disable
 854
 855                                 RW
 856
 857 ********
 858 Humidity
 859 ********
 860
 861 `humidity[1-*]_input`
 862                                 Humidity
 863
 864                                 Unit: milli-percent (per cent mille, pcm)
 865
 866                                 RO
 867
 868
 869 `humidity[1-*]_enable`
 870                                 Enable or disable the sensors
 871
 872                                 When disabled the sensor read will return
 873                                 -ENODATA.
 874
 875                                 - 1: Enable
 876                                 - 0: Disable
 877
 878                                 RW
 879
 880 ******
 881 Alarms
 882 ******
 883
 884 Each channel or limit may have an associated alarm file, containing a
 885 boolean value. 1 means than an alarm condition exists, 0 means no alarm.
 886
 887 Usually a given chip will either use channel-related alarms, or
 888 limit-related alarms, not both. The driver should just reflect the hardware
 889 implementation.
 890
 891 +-------------------------------+-----------------------+
 892 | **`in[0-*]_alarm`,            | Channel alarm         |
 893 | `curr[1-*]_alarm`,            |                       |
 894 | `power[1-*]_alarm`,           |   - 0: no alarm       |
 895 | `fan[1-*]_alarm`,             |   - 1: alarm          |
 896 | `temp[1-*]_alarm`**           |                       |
 897 |                               |   RO                  |
 898 +-------------------------------+-----------------------+
 899
 900 **OR**
 901
 902 +-------------------------------+-----------------------+
 903 | **`in[0-*]_min_alarm`,        | Limit alarm           |
 904 | `in[0-*]_max_alarm`,          |                       |
 905 | `in[0-*]_lcrit_alarm`,        |   - 0: no alarm       |
 906 | `in[0-*]_crit_alarm`,         |   - 1: alarm          |
 907 | `curr[1-*]_min_alarm`,        |                       |
 908 | `curr[1-*]_max_alarm`,        | RO                    |
 909 | `curr[1-*]_lcrit_alarm`,      |                       |
 910 | `curr[1-*]_crit_alarm`,       |                       |
 911 | `power[1-*]_cap_alarm`,       |                       |
 912 | `power[1-*]_max_alarm`,       |                       |
 913 | `power[1-*]_crit_alarm`,      |                       |
 914 | `fan[1-*]_min_alarm`,         |                       |
 915 | `fan[1-*]_max_alarm`,         |                       |
 916 | `temp[1-*]_min_alarm`,        |                       |
 917 | `temp[1-*]_max_alarm`,        |                       |
 918 | `temp[1-*]_lcrit_alarm`,      |                       |
 919 | `temp[1-*]_crit_alarm`,       |                       |
 920 | `temp[1-*]_emergency_alarm`** |                       |
 921 +-------------------------------+-----------------------+
 922
 923 Each input channel may have an associated fault file. This can be used
 924 to notify open diodes, unconnected fans etc. where the hardware
 925 supports it. When this boolean has value 1, the measurement for that
 926 channel should not be trusted.
 927
 928 `fan[1-*]_fault` / `temp[1-*]_fault`
 929                 Input fault condition
 930
 931                 - 0: no fault occurred
 932                 - 1: fault condition
 933
 934                 RO
 935
 936 Some chips also offer the possibility to get beeped when an alarm occurs:
 937
 938 `beep_enable`
 939                 Master beep enable
 940
 941                 - 0: no beeps
 942                 - 1: beeps
 943
 944                 RW
 945
 946 `in[0-*]_beep`, `curr[1-*]_beep`, `fan[1-*]_beep`, `temp[1-*]_beep`,
 947                 Channel beep
 948
 949                 - 0: disable
 950                 - 1: enable
 951
 952                 RW
 953
 954 In theory, a chip could provide per-limit beep masking, but no such chip
 955 was seen so far.
 956
 957 Old drivers provided a different, non-standard interface to alarms and
 958 beeps. These interface files are deprecated, but will be kept around
 959 for compatibility reasons:
 960
 961 `alarms`
 962                 Alarm bitmask.
 963
 964                 RO
 965
 966                 Integer representation of one to four bytes.
 967
 968                 A '1' bit means an alarm.
 969
 970                 Chips should be programmed for 'comparator' mode so that
 971                 the alarm will 'come back' after you read the register
 972                 if it is still valid.
 973
 974                 Generally a direct representation of a chip's internal
 975                 alarm registers; there is no standard for the position
 976                 of individual bits. For this reason, the use of this
 977                 interface file for new drivers is discouraged. Use
 978                 `individual *_alarm` and `*_fault` files instead.
 979                 Bits are defined in kernel/include/sensors.h.
 980
 981 `beep_mask`
 982                 Bitmask for beep.
 983                 Same format as 'alarms' with the same bit locations,
 984                 use discouraged for the same reason. Use individual
 985                 `*_beep` files instead.
 986                 RW
 987
 988
 989 *******************
 990 Intrusion detection
 991 *******************
 992
 993 `intrusion[0-*]_alarm`
 994                 Chassis intrusion detection
 995
 996                 - 0: OK
 997                 - 1: intrusion detected
 998
 999                 RW
1000
1001                 Contrary to regular alarm flags which clear themselves
1002                 automatically when read, this one sticks until cleared by
1003                 the user. This is done by writing 0 to the file. Writing
1004                 other values is unsupported.
1005
1006 `intrusion[0-*]_beep`
1007                 Chassis intrusion beep
1008
1009                 0: disable
1010                 1: enable
1011
1012                 RW
1013
1014 ****************************
1015 Average sample configuration
1016 ****************************
1017
1018 Devices allowing for reading {in,power,curr,temp}_average values may export
1019 attributes for controlling number of samples used to compute average.
1020
1021 +--------------+---------------------------------------------------------------+
1022 | samples      | Sets number of average samples for all types of measurements. |
1023 |              |                                                               |
1024 |              | RW                                                            |
1025 +--------------+---------------------------------------------------------------+
1026 | in_samples   | Sets number of average samples for specific type of           |
1027 | power_samples| measurements.                                                 |
1028 | curr_samples |                                                               |
1029 | temp_samples | Note that on some devices it won't be possible to set all of  |
1030 |              | them to different values so changing one might also change    |
1031 |              | some others.                                                  |
1032 |              |                                                               |
1033 |              | RW                                                            |
1034 +--------------+---------------------------------------------------------------+
1035
1036 sysfs attribute writes interpretation
1037 -------------------------------------
1038
1039 hwmon sysfs attributes always contain numbers, so the first thing to do is to
1040 convert the input to a number, there are 2 ways todo this depending whether
1041 the number can be negative or not::
1042
1043         unsigned long u = simple_strtoul(buf, NULL, 10);
1044         long s = simple_strtol(buf, NULL, 10);
1045
1046 With buf being the buffer with the user input being passed by the kernel.
1047 Notice that we do not use the second argument of strto[u]l, and thus cannot
1048 tell when 0 is returned, if this was really 0 or is caused by invalid input.
1049 This is done deliberately as checking this everywhere would add a lot of
1050 code to the kernel.
1051
1052 Notice that it is important to always store the converted value in an
1053 unsigned long or long, so that no wrap around can happen before any further
1054 checking.
1055
1056 After the input string is converted to an (unsigned) long, the value should be
1057 checked if its acceptable. Be careful with further conversions on the value
1058 before checking it for validity, as these conversions could still cause a wrap
1059 around before the check. For example do not multiply the result, and only
1060 add/subtract if it has been divided before the add/subtract.
1061
1062 What to do if a value is found to be invalid, depends on the type of the
1063 sysfs attribute that is being set. If it is a continuous setting like a
1064 tempX_max or inX_max attribute, then the value should be clamped to its
1065 limits using clamp_val(value, min_limit, max_limit). If it is not continuous
1066 like for example a tempX_type, then when an invalid value is written,
1067 -EINVAL should be returned.
1068
1069 Example1, temp1_max, register is a signed 8 bit value (-128 - 127 degrees)::
1070
1071         long v = simple_strtol(buf, NULL, 10) / 1000;
1072         v = clamp_val(v, -128, 127);
1073         /* write v to register */
1074
1075 Example2, fan divider setting, valid values 2, 4 and 8::
1076
1077         unsigned long v = simple_strtoul(buf, NULL, 10);
1078
1079         switch (v) {
1080         case 2: v = 1; break;
1081         case 4: v = 2; break;
1082         case 8: v = 3; break;
1083         default:
1084                 return -EINVAL;
1085         }
1086         /* write v to register */