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1da177e4 LT |
1 | Naming and data format standards for sysfs files |
2 | ------------------------------------------------ | |
3 | ||
4 | The libsensors library offers an interface to the raw sensors data | |
125ff808 JD |
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. | |
1da177e4 LT |
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 | ||
740e06a8 | 22 | For this reason, even if we aim at a chip-independent libsensors, it will |
1da177e4 LT |
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 | ||
1da177e4 | 33 | Each chip gets its own directory in the sysfs /sys/devices tree. To |
740e06a8 JD |
34 | find all sensor chips, it is easier to follow the device symlinks from |
35 | /sys/class/hwmon/hwmon*. | |
1da177e4 | 36 | |
125ff808 JD |
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 | ||
740e06a8 | 44 | All sysfs values are fixed point numbers. |
1da177e4 LT |
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 | ||
2ed42633 HG |
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. | |
1da177e4 LT |
67 | |
68 | ------------------------------------------------------------------------- | |
69 | ||
057bc350 RM |
70 | [0-*] denotes any positive number starting from 0 |
71 | [1-*] denotes any positive number starting from 1 | |
72 | RO read only value | |
73 | RW read/write value | |
74 | ||
75 | Read/write values may be read-only for some chips, depending on the | |
76 | hardware implementation. | |
77 | ||
176544dc JD |
78 | All entries (except name) are optional, and should only be created in a |
79 | given driver if the chip has the feature. | |
80 | ||
81 | ||
82 | ******** | |
83 | * Name * | |
84 | ******** | |
85 | ||
86 | name The chip name. | |
87 | This should be a short, lowercase string, not containing | |
88 | spaces nor dashes, representing the chip name. This is | |
89 | the only mandatory attribute. | |
90 | I2C devices get this attribute created automatically. | |
91 | RO | |
92 | ||
740e06a8 | 93 | |
1da177e4 LT |
94 | ************ |
95 | * Voltages * | |
96 | ************ | |
97 | ||
057bc350 | 98 | in[0-*]_min Voltage min value. |
1da177e4 | 99 | Unit: millivolt |
057bc350 | 100 | RW |
1da177e4 | 101 | |
057bc350 | 102 | in[0-*]_max Voltage max value. |
1da177e4 | 103 | Unit: millivolt |
057bc350 | 104 | RW |
1da177e4 | 105 | |
057bc350 | 106 | in[0-*]_input Voltage input value. |
1da177e4 | 107 | Unit: millivolt |
057bc350 RM |
108 | RO |
109 | Voltage measured on the chip pin. | |
1da177e4 LT |
110 | Actual voltage depends on the scaling resistors on the |
111 | motherboard, as recommended in the chip datasheet. | |
112 | This varies by chip and by motherboard. | |
113 | Because of this variation, values are generally NOT scaled | |
114 | by the chip driver, and must be done by the application. | |
115 | However, some drivers (notably lm87 and via686a) | |
057bc350 | 116 | do scale, because of internal resistors built into a chip. |
176544dc JD |
117 | These drivers will output the actual voltage. Rule of |
118 | thumb: drivers should report the voltage values at the | |
119 | "pins" of the chip. | |
120 | ||
121 | in[0-*]_label Suggested voltage channel label. | |
122 | Text string | |
123 | Should only be created if the driver has hints about what | |
124 | this voltage channel is being used for, and user-space | |
125 | doesn't. In all other cases, the label is provided by | |
126 | user-space. | |
127 | RO | |
1da177e4 | 128 | |
057bc350 | 129 | cpu[0-*]_vid CPU core reference voltage. |
1da177e4 | 130 | Unit: millivolt |
057bc350 | 131 | RO |
1da177e4 LT |
132 | Not always correct. |
133 | ||
134 | vrm Voltage Regulator Module version number. | |
057bc350 RM |
135 | RW (but changing it should no more be necessary) |
136 | Originally the VRM standard version multiplied by 10, but now | |
137 | an arbitrary number, as not all standards have a version | |
138 | number. | |
1da177e4 LT |
139 | Affects the way the driver calculates the CPU core reference |
140 | voltage from the vid pins. | |
141 | ||
057bc350 RM |
142 | Also see the Alarms section for status flags associated with voltages. |
143 | ||
1da177e4 LT |
144 | |
145 | ******** | |
146 | * Fans * | |
147 | ******** | |
148 | ||
057bc350 | 149 | fan[1-*]_min Fan minimum value |
1da177e4 | 150 | Unit: revolution/min (RPM) |
057bc350 | 151 | RW |
1da177e4 | 152 | |
057bc350 | 153 | fan[1-*]_input Fan input value. |
1da177e4 | 154 | Unit: revolution/min (RPM) |
057bc350 | 155 | RO |
1da177e4 | 156 | |
057bc350 | 157 | fan[1-*]_div Fan divisor. |
1da177e4 | 158 | Integer value in powers of two (1, 2, 4, 8, 16, 32, 64, 128). |
057bc350 | 159 | RW |
1da177e4 LT |
160 | Some chips only support values 1, 2, 4 and 8. |
161 | Note that this is actually an internal clock divisor, which | |
162 | affects the measurable speed range, not the read value. | |
163 | ||
2dbc514a JD |
164 | fan[1-*]_target |
165 | Desired fan speed | |
166 | Unit: revolution/min (RPM) | |
167 | RW | |
168 | Only makes sense if the chip supports closed-loop fan speed | |
169 | control based on the measured fan speed. | |
170 | ||
176544dc JD |
171 | fan[1-*]_label Suggested fan channel label. |
172 | Text string | |
173 | Should only be created if the driver has hints about what | |
174 | this fan channel is being used for, and user-space doesn't. | |
175 | In all other cases, the label is provided by user-space. | |
176 | RO | |
177 | ||
057bc350 RM |
178 | Also see the Alarms section for status flags associated with fans. |
179 | ||
180 | ||
1da177e4 LT |
181 | ******* |
182 | * PWM * | |
183 | ******* | |
184 | ||
057bc350 | 185 | pwm[1-*] Pulse width modulation fan control. |
1da177e4 | 186 | Integer value in the range 0 to 255 |
057bc350 | 187 | RW |
1da177e4 LT |
188 | 255 is max or 100%. |
189 | ||
057bc350 | 190 | pwm[1-*]_enable |
875f25d5 JD |
191 | Fan speed control method: |
192 | 0: no fan speed control (i.e. fan at full speed) | |
193 | 1: manual fan speed control enabled (using pwm[1-*]) | |
194 | 2+: automatic fan speed control enabled | |
f8d0c19a JD |
195 | Check individual chip documentation files for automatic mode |
196 | details. | |
057bc350 RM |
197 | RW |
198 | ||
f8d0c19a JD |
199 | pwm[1-*]_mode 0: DC mode (direct current) |
200 | 1: PWM mode (pulse-width modulation) | |
201 | RW | |
202 | ||
203 | pwm[1-*]_freq Base PWM frequency in Hz. | |
204 | Only possibly available when pwmN_mode is PWM, but not always | |
205 | present even then. | |
057bc350 | 206 | RW |
1da177e4 LT |
207 | |
208 | pwm[1-*]_auto_channels_temp | |
209 | Select which temperature channels affect this PWM output in | |
210 | auto mode. Bitfield, 1 is temp1, 2 is temp2, 4 is temp3 etc... | |
211 | Which values are possible depend on the chip used. | |
057bc350 | 212 | RW |
1da177e4 LT |
213 | |
214 | pwm[1-*]_auto_point[1-*]_pwm | |
215 | pwm[1-*]_auto_point[1-*]_temp | |
216 | pwm[1-*]_auto_point[1-*]_temp_hyst | |
217 | Define the PWM vs temperature curve. Number of trip points is | |
218 | chip-dependent. Use this for chips which associate trip points | |
219 | to PWM output channels. | |
057bc350 | 220 | RW |
1da177e4 LT |
221 | |
222 | OR | |
223 | ||
224 | temp[1-*]_auto_point[1-*]_pwm | |
225 | temp[1-*]_auto_point[1-*]_temp | |
226 | temp[1-*]_auto_point[1-*]_temp_hyst | |
227 | Define the PWM vs temperature curve. Number of trip points is | |
228 | chip-dependent. Use this for chips which associate trip points | |
229 | to temperature channels. | |
057bc350 | 230 | RW |
1da177e4 LT |
231 | |
232 | ||
233 | **************** | |
234 | * Temperatures * | |
235 | **************** | |
236 | ||
057bc350 | 237 | temp[1-*]_type Sensor type selection. |
b26f9330 | 238 | Integers 1 to 6 |
057bc350 | 239 | RW |
1da177e4 LT |
240 | 1: PII/Celeron Diode |
241 | 2: 3904 transistor | |
242 | 3: thermal diode | |
b26f9330 | 243 | 4: thermistor |
61db011d RM |
244 | 5: AMD AMDSI |
245 | 6: Intel PECI | |
1da177e4 LT |
246 | Not all types are supported by all chips |
247 | ||
057bc350 | 248 | temp[1-*]_max Temperature max value. |
740e06a8 | 249 | Unit: millidegree Celsius (or millivolt, see below) |
057bc350 | 250 | RW |
1da177e4 | 251 | |
057bc350 | 252 | temp[1-*]_min Temperature min value. |
740e06a8 | 253 | Unit: millidegree Celsius |
057bc350 | 254 | RW |
1da177e4 | 255 | |
057bc350 | 256 | temp[1-*]_max_hyst |
1da177e4 | 257 | Temperature hysteresis value for max limit. |
740e06a8 | 258 | Unit: millidegree Celsius |
1da177e4 LT |
259 | Must be reported as an absolute temperature, NOT a delta |
260 | from the max value. | |
057bc350 | 261 | RW |
1da177e4 | 262 | |
057bc350 | 263 | temp[1-*]_input Temperature input value. |
740e06a8 | 264 | Unit: millidegree Celsius |
057bc350 | 265 | RO |
1da177e4 | 266 | |
057bc350 | 267 | temp[1-*]_crit Temperature critical value, typically greater than |
1da177e4 | 268 | corresponding temp_max values. |
740e06a8 | 269 | Unit: millidegree Celsius |
057bc350 | 270 | RW |
1da177e4 | 271 | |
057bc350 | 272 | temp[1-*]_crit_hyst |
1da177e4 | 273 | Temperature hysteresis value for critical limit. |
740e06a8 | 274 | Unit: millidegree Celsius |
1da177e4 LT |
275 | Must be reported as an absolute temperature, NOT a delta |
276 | from the critical value. | |
057bc350 | 277 | RW |
1da177e4 | 278 | |
176544dc | 279 | temp[1-*]_offset |
59ac8367 HR |
280 | Temperature offset which is added to the temperature reading |
281 | by the chip. | |
282 | Unit: millidegree Celsius | |
283 | Read/Write value. | |
284 | ||
176544dc JD |
285 | temp[1-*]_label Suggested temperature channel label. |
286 | Text string | |
287 | Should only be created if the driver has hints about what | |
288 | this temperature channel is being used for, and user-space | |
289 | doesn't. In all other cases, the label is provided by | |
290 | user-space. | |
291 | RO | |
1da177e4 | 292 | |
740e06a8 JD |
293 | Some chips measure temperature using external thermistors and an ADC, and |
294 | report the temperature measurement as a voltage. Converting this voltage | |
295 | back to a temperature (or the other way around for limits) requires | |
296 | mathematical functions not available in the kernel, so the conversion | |
297 | must occur in user space. For these chips, all temp* files described | |
298 | above should contain values expressed in millivolt instead of millidegree | |
299 | Celsius. In other words, such temperature channels are handled as voltage | |
300 | channels by the driver. | |
301 | ||
057bc350 RM |
302 | Also see the Alarms section for status flags associated with temperatures. |
303 | ||
1da177e4 LT |
304 | |
305 | ************ | |
306 | * Currents * | |
307 | ************ | |
308 | ||
309 | Note that no known chip provides current measurements as of writing, | |
310 | so this part is theoretical, so to say. | |
311 | ||
057bc350 | 312 | curr[1-*]_max Current max value |
1da177e4 | 313 | Unit: milliampere |
057bc350 | 314 | RW |
1da177e4 | 315 | |
057bc350 | 316 | curr[1-*]_min Current min value. |
1da177e4 | 317 | Unit: milliampere |
057bc350 | 318 | RW |
1da177e4 | 319 | |
057bc350 | 320 | curr[1-*]_input Current input value |
1da177e4 | 321 | Unit: milliampere |
057bc350 | 322 | RO |
1da177e4 | 323 | |
38fb56a2 DW |
324 | ********* |
325 | * Power * | |
326 | ********* | |
327 | ||
328 | power[1-*]_average Average power use | |
329 | Unit: microWatt | |
330 | RO | |
331 | ||
ddedc658 DW |
332 | power[1-*]_average_interval Power use averaging interval |
333 | Unit: milliseconds | |
334 | RW | |
335 | ||
38fb56a2 DW |
336 | power[1-*]_average_highest Historical average maximum power use |
337 | Unit: microWatt | |
338 | RO | |
339 | ||
340 | power[1-*]_average_lowest Historical average minimum power use | |
341 | Unit: microWatt | |
342 | RO | |
343 | ||
344 | power[1-*]_input Instantaneous power use | |
345 | Unit: microWatt | |
346 | RO | |
347 | ||
348 | power[1-*]_input_highest Historical maximum power use | |
349 | Unit: microWatt | |
350 | RO | |
351 | ||
352 | power[1-*]_input_lowest Historical minimum power use | |
353 | Unit: microWatt | |
354 | RO | |
355 | ||
356 | power[1-*]_reset_history Reset input_highest, input_lowest, | |
357 | average_highest and average_lowest. | |
358 | WO | |
1da177e4 | 359 | |
ddedc658 DW |
360 | ********** |
361 | * Energy * | |
362 | ********** | |
363 | ||
364 | energy[1-*]_input Cumulative energy use | |
365 | Unit: microJoule | |
366 | RO | |
367 | ||
400b48ec JD |
368 | ********** |
369 | * Alarms * | |
370 | ********** | |
371 | ||
372 | Each channel or limit may have an associated alarm file, containing a | |
373 | boolean value. 1 means than an alarm condition exists, 0 means no alarm. | |
374 | ||
375 | Usually a given chip will either use channel-related alarms, or | |
376 | limit-related alarms, not both. The driver should just reflect the hardware | |
377 | implementation. | |
378 | ||
057bc350 RM |
379 | in[0-*]_alarm |
380 | fan[1-*]_alarm | |
381 | temp[1-*]_alarm | |
400b48ec | 382 | Channel alarm |
057bc350 RM |
383 | 0: no alarm |
384 | 1: alarm | |
385 | RO | |
400b48ec JD |
386 | |
387 | OR | |
388 | ||
057bc350 RM |
389 | in[0-*]_min_alarm |
390 | in[0-*]_max_alarm | |
391 | fan[1-*]_min_alarm | |
392 | temp[1-*]_min_alarm | |
393 | temp[1-*]_max_alarm | |
394 | temp[1-*]_crit_alarm | |
400b48ec | 395 | Limit alarm |
057bc350 RM |
396 | 0: no alarm |
397 | 1: alarm | |
398 | RO | |
400b48ec JD |
399 | |
400 | Each input channel may have an associated fault file. This can be used | |
401 | to notify open diodes, unconnected fans etc. where the hardware | |
402 | supports it. When this boolean has value 1, the measurement for that | |
403 | channel should not be trusted. | |
404 | ||
7817a39e JD |
405 | in[0-*]_fault |
406 | fan[1-*]_fault | |
407 | temp[1-*]_fault | |
400b48ec | 408 | Input fault condition |
057bc350 RM |
409 | 0: no fault occured |
410 | 1: fault condition | |
411 | RO | |
400b48ec JD |
412 | |
413 | Some chips also offer the possibility to get beeped when an alarm occurs: | |
414 | ||
415 | beep_enable Master beep enable | |
057bc350 RM |
416 | 0: no beeps |
417 | 1: beeps | |
418 | RW | |
400b48ec | 419 | |
057bc350 RM |
420 | in[0-*]_beep |
421 | fan[1-*]_beep | |
422 | temp[1-*]_beep | |
400b48ec | 423 | Channel beep |
057bc350 RM |
424 | 0: disable |
425 | 1: enable | |
426 | RW | |
400b48ec JD |
427 | |
428 | In theory, a chip could provide per-limit beep masking, but no such chip | |
429 | was seen so far. | |
430 | ||
431 | Old drivers provided a different, non-standard interface to alarms and | |
432 | beeps. These interface files are deprecated, but will be kept around | |
433 | for compatibility reasons: | |
1da177e4 LT |
434 | |
435 | alarms Alarm bitmask. | |
057bc350 | 436 | RO |
1da177e4 LT |
437 | Integer representation of one to four bytes. |
438 | A '1' bit means an alarm. | |
439 | Chips should be programmed for 'comparator' mode so that | |
440 | the alarm will 'come back' after you read the register | |
441 | if it is still valid. | |
442 | Generally a direct representation of a chip's internal | |
443 | alarm registers; there is no standard for the position | |
400b48ec JD |
444 | of individual bits. For this reason, the use of this |
445 | interface file for new drivers is discouraged. Use | |
446 | individual *_alarm and *_fault files instead. | |
1da177e4 LT |
447 | Bits are defined in kernel/include/sensors.h. |
448 | ||
1da177e4 | 449 | beep_mask Bitmask for beep. |
400b48ec JD |
450 | Same format as 'alarms' with the same bit locations, |
451 | use discouraged for the same reason. Use individual | |
452 | *_beep files instead. | |
057bc350 | 453 | RW |
2ed42633 HG |
454 | |
455 | ||
456 | sysfs attribute writes interpretation | |
457 | ------------------------------------- | |
458 | ||
459 | hwmon sysfs attributes always contain numbers, so the first thing to do is to | |
460 | convert the input to a number, there are 2 ways todo this depending whether | |
461 | the number can be negative or not: | |
462 | unsigned long u = simple_strtoul(buf, NULL, 10); | |
463 | long s = simple_strtol(buf, NULL, 10); | |
464 | ||
465 | With buf being the buffer with the user input being passed by the kernel. | |
466 | Notice that we do not use the second argument of strto[u]l, and thus cannot | |
467 | tell when 0 is returned, if this was really 0 or is caused by invalid input. | |
468 | This is done deliberately as checking this everywhere would add a lot of | |
469 | code to the kernel. | |
470 | ||
471 | Notice that it is important to always store the converted value in an | |
472 | unsigned long or long, so that no wrap around can happen before any further | |
473 | checking. | |
474 | ||
475 | After the input string is converted to an (unsigned) long, the value should be | |
476 | checked if its acceptable. Be careful with further conversions on the value | |
477 | before checking it for validity, as these conversions could still cause a wrap | |
478 | around before the check. For example do not multiply the result, and only | |
479 | add/subtract if it has been divided before the add/subtract. | |
480 | ||
481 | What to do if a value is found to be invalid, depends on the type of the | |
482 | sysfs attribute that is being set. If it is a continuous setting like a | |
483 | tempX_max or inX_max attribute, then the value should be clamped to its | |
484 | limits using SENSORS_LIMIT(value, min_limit, max_limit). If it is not | |
485 | continuous like for example a tempX_type, then when an invalid value is | |
486 | written, -EINVAL should be returned. | |
487 | ||
488 | Example1, temp1_max, register is a signed 8 bit value (-128 - 127 degrees): | |
5fbea518 JD |
489 | |
490 | long v = simple_strtol(buf, NULL, 10) / 1000; | |
491 | v = SENSORS_LIMIT(v, -128, 127); | |
492 | /* write v to register */ | |
2ed42633 HG |
493 | |
494 | Example2, fan divider setting, valid values 2, 4 and 8: | |
5fbea518 JD |
495 | |
496 | unsigned long v = simple_strtoul(buf, NULL, 10); | |
497 | ||
498 | switch (v) { | |
499 | case 2: v = 1; break; | |
500 | case 4: v = 2; break; | |
501 | case 8: v = 3; break; | |
502 | default: | |
503 | return -EINVAL; | |
504 | } | |
505 | /* write v to register */ |