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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 | |
5 | through the sysfs interface. See libsensors documentation and source for | |
740e06a8 JD |
6 | further information. As of writing this document, libsensors |
7 | (from lm_sensors 2.8.3) is heavily chip-dependent. Adding or updating | |
1da177e4 LT |
8 | support for any given chip requires modifying the library's code. |
9 | This is because libsensors was written for the procfs interface | |
10 | older kernel modules were using, which wasn't standardized enough. | |
11 | Recent versions of libsensors (from lm_sensors 2.8.2 and later) have | |
12 | support for the sysfs interface, though. | |
13 | ||
740e06a8 | 14 | The new sysfs interface was designed to be as chip-independent as |
1da177e4 LT |
15 | possible. |
16 | ||
17 | Note that motherboards vary widely in the connections to sensor chips. | |
18 | There is no standard that ensures, for example, that the second | |
19 | temperature sensor is connected to the CPU, or that the second fan is on | |
20 | the CPU. Also, some values reported by the chips need some computation | |
21 | before they make full sense. For example, most chips can only measure | |
22 | voltages between 0 and +4V. Other voltages are scaled back into that | |
23 | range using external resistors. Since the values of these resistors | |
24 | can change from motherboard to motherboard, the conversions cannot be | |
25 | hard coded into the driver and have to be done in user space. | |
26 | ||
740e06a8 | 27 | For this reason, even if we aim at a chip-independent libsensors, it will |
1da177e4 LT |
28 | still require a configuration file (e.g. /etc/sensors.conf) for proper |
29 | values conversion, labeling of inputs and hiding of unused inputs. | |
30 | ||
31 | An alternative method that some programs use is to access the sysfs | |
32 | files directly. This document briefly describes the standards that the | |
33 | drivers follow, so that an application program can scan for entries and | |
34 | access this data in a simple and consistent way. That said, such programs | |
35 | will have to implement conversion, labeling and hiding of inputs. For | |
36 | this reason, it is still not recommended to bypass the library. | |
37 | ||
38 | If you are developing a userspace application please send us feedback on | |
39 | this standard. | |
40 | ||
41 | Note that this standard isn't completely established yet, so it is subject | |
740e06a8 JD |
42 | to changes. If you are writing a new hardware monitoring driver those |
43 | features can't seem to fit in this interface, please contact us with your | |
44 | extension proposal. Keep in mind that backward compatibility must be | |
45 | preserved. | |
1da177e4 LT |
46 | |
47 | Each chip gets its own directory in the sysfs /sys/devices tree. To | |
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48 | find all sensor chips, it is easier to follow the device symlinks from |
49 | /sys/class/hwmon/hwmon*. | |
1da177e4 | 50 | |
740e06a8 | 51 | All sysfs values are fixed point numbers. |
1da177e4 LT |
52 | |
53 | There is only one value per file, unlike the older /proc specification. | |
54 | The common scheme for files naming is: <type><number>_<item>. Usual | |
55 | types for sensor chips are "in" (voltage), "temp" (temperature) and | |
56 | "fan" (fan). Usual items are "input" (measured value), "max" (high | |
57 | threshold, "min" (low threshold). Numbering usually starts from 1, | |
58 | except for voltages which start from 0 (because most data sheets use | |
59 | this). A number is always used for elements that can be present more | |
60 | than once, even if there is a single element of the given type on the | |
61 | specific chip. Other files do not refer to a specific element, so | |
62 | they have a simple name, and no number. | |
63 | ||
64 | Alarms are direct indications read from the chips. The drivers do NOT | |
65 | make comparisons of readings to thresholds. This allows violations | |
66 | between readings to be caught and alarmed. The exact definition of an | |
67 | alarm (for example, whether a threshold must be met or must be exceeded | |
68 | to cause an alarm) is chip-dependent. | |
69 | ||
2ed42633 HG |
70 | When setting values of hwmon sysfs attributes, the string representation of |
71 | the desired value must be written, note that strings which are not a number | |
72 | are interpreted as 0! For more on how written strings are interpreted see the | |
73 | "sysfs attribute writes interpretation" section at the end of this file. | |
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74 | |
75 | ------------------------------------------------------------------------- | |
76 | ||
057bc350 RM |
77 | [0-*] denotes any positive number starting from 0 |
78 | [1-*] denotes any positive number starting from 1 | |
79 | RO read only value | |
80 | RW read/write value | |
81 | ||
82 | Read/write values may be read-only for some chips, depending on the | |
83 | hardware implementation. | |
84 | ||
176544dc JD |
85 | All entries (except name) are optional, and should only be created in a |
86 | given driver if the chip has the feature. | |
87 | ||
88 | ||
89 | ******** | |
90 | * Name * | |
91 | ******** | |
92 | ||
93 | name The chip name. | |
94 | This should be a short, lowercase string, not containing | |
95 | spaces nor dashes, representing the chip name. This is | |
96 | the only mandatory attribute. | |
97 | I2C devices get this attribute created automatically. | |
98 | RO | |
99 | ||
740e06a8 | 100 | |
1da177e4 LT |
101 | ************ |
102 | * Voltages * | |
103 | ************ | |
104 | ||
057bc350 | 105 | in[0-*]_min Voltage min value. |
1da177e4 | 106 | Unit: millivolt |
057bc350 | 107 | RW |
1da177e4 | 108 | |
057bc350 | 109 | in[0-*]_max Voltage max value. |
1da177e4 | 110 | Unit: millivolt |
057bc350 | 111 | RW |
1da177e4 | 112 | |
057bc350 | 113 | in[0-*]_input Voltage input value. |
1da177e4 | 114 | Unit: millivolt |
057bc350 RM |
115 | RO |
116 | Voltage measured on the chip pin. | |
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117 | Actual voltage depends on the scaling resistors on the |
118 | motherboard, as recommended in the chip datasheet. | |
119 | This varies by chip and by motherboard. | |
120 | Because of this variation, values are generally NOT scaled | |
121 | by the chip driver, and must be done by the application. | |
122 | However, some drivers (notably lm87 and via686a) | |
057bc350 | 123 | do scale, because of internal resistors built into a chip. |
176544dc JD |
124 | These drivers will output the actual voltage. Rule of |
125 | thumb: drivers should report the voltage values at the | |
126 | "pins" of the chip. | |
127 | ||
128 | in[0-*]_label Suggested voltage channel label. | |
129 | Text string | |
130 | Should only be created if the driver has hints about what | |
131 | this voltage channel is being used for, and user-space | |
132 | doesn't. In all other cases, the label is provided by | |
133 | user-space. | |
134 | RO | |
1da177e4 | 135 | |
057bc350 | 136 | cpu[0-*]_vid CPU core reference voltage. |
1da177e4 | 137 | Unit: millivolt |
057bc350 | 138 | RO |
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139 | Not always correct. |
140 | ||
141 | vrm Voltage Regulator Module version number. | |
057bc350 RM |
142 | RW (but changing it should no more be necessary) |
143 | Originally the VRM standard version multiplied by 10, but now | |
144 | an arbitrary number, as not all standards have a version | |
145 | number. | |
1da177e4 LT |
146 | Affects the way the driver calculates the CPU core reference |
147 | voltage from the vid pins. | |
148 | ||
057bc350 RM |
149 | Also see the Alarms section for status flags associated with voltages. |
150 | ||
1da177e4 LT |
151 | |
152 | ******** | |
153 | * Fans * | |
154 | ******** | |
155 | ||
057bc350 | 156 | fan[1-*]_min Fan minimum value |
1da177e4 | 157 | Unit: revolution/min (RPM) |
057bc350 | 158 | RW |
1da177e4 | 159 | |
057bc350 | 160 | fan[1-*]_input Fan input value. |
1da177e4 | 161 | Unit: revolution/min (RPM) |
057bc350 | 162 | RO |
1da177e4 | 163 | |
057bc350 | 164 | fan[1-*]_div Fan divisor. |
1da177e4 | 165 | Integer value in powers of two (1, 2, 4, 8, 16, 32, 64, 128). |
057bc350 | 166 | RW |
1da177e4 LT |
167 | Some chips only support values 1, 2, 4 and 8. |
168 | Note that this is actually an internal clock divisor, which | |
169 | affects the measurable speed range, not the read value. | |
170 | ||
2dbc514a JD |
171 | fan[1-*]_target |
172 | Desired fan speed | |
173 | Unit: revolution/min (RPM) | |
174 | RW | |
175 | Only makes sense if the chip supports closed-loop fan speed | |
176 | control based on the measured fan speed. | |
177 | ||
176544dc JD |
178 | fan[1-*]_label Suggested fan channel label. |
179 | Text string | |
180 | Should only be created if the driver has hints about what | |
181 | this fan channel is being used for, and user-space doesn't. | |
182 | In all other cases, the label is provided by user-space. | |
183 | RO | |
184 | ||
057bc350 RM |
185 | Also see the Alarms section for status flags associated with fans. |
186 | ||
187 | ||
1da177e4 LT |
188 | ******* |
189 | * PWM * | |
190 | ******* | |
191 | ||
057bc350 | 192 | pwm[1-*] Pulse width modulation fan control. |
1da177e4 | 193 | Integer value in the range 0 to 255 |
057bc350 | 194 | RW |
1da177e4 LT |
195 | 255 is max or 100%. |
196 | ||
057bc350 | 197 | pwm[1-*]_enable |
875f25d5 JD |
198 | Fan speed control method: |
199 | 0: no fan speed control (i.e. fan at full speed) | |
200 | 1: manual fan speed control enabled (using pwm[1-*]) | |
201 | 2+: automatic fan speed control enabled | |
f8d0c19a JD |
202 | Check individual chip documentation files for automatic mode |
203 | details. | |
057bc350 RM |
204 | RW |
205 | ||
f8d0c19a JD |
206 | pwm[1-*]_mode 0: DC mode (direct current) |
207 | 1: PWM mode (pulse-width modulation) | |
208 | RW | |
209 | ||
210 | pwm[1-*]_freq Base PWM frequency in Hz. | |
211 | Only possibly available when pwmN_mode is PWM, but not always | |
212 | present even then. | |
057bc350 | 213 | RW |
1da177e4 LT |
214 | |
215 | pwm[1-*]_auto_channels_temp | |
216 | Select which temperature channels affect this PWM output in | |
217 | auto mode. Bitfield, 1 is temp1, 2 is temp2, 4 is temp3 etc... | |
218 | Which values are possible depend on the chip used. | |
057bc350 | 219 | RW |
1da177e4 LT |
220 | |
221 | pwm[1-*]_auto_point[1-*]_pwm | |
222 | pwm[1-*]_auto_point[1-*]_temp | |
223 | pwm[1-*]_auto_point[1-*]_temp_hyst | |
224 | Define the PWM vs temperature curve. Number of trip points is | |
225 | chip-dependent. Use this for chips which associate trip points | |
226 | to PWM output channels. | |
057bc350 | 227 | RW |
1da177e4 LT |
228 | |
229 | OR | |
230 | ||
231 | temp[1-*]_auto_point[1-*]_pwm | |
232 | temp[1-*]_auto_point[1-*]_temp | |
233 | temp[1-*]_auto_point[1-*]_temp_hyst | |
234 | Define the PWM vs temperature curve. Number of trip points is | |
235 | chip-dependent. Use this for chips which associate trip points | |
236 | to temperature channels. | |
057bc350 | 237 | RW |
1da177e4 LT |
238 | |
239 | ||
240 | **************** | |
241 | * Temperatures * | |
242 | **************** | |
243 | ||
057bc350 | 244 | temp[1-*]_type Sensor type selection. |
b26f9330 | 245 | Integers 1 to 6 |
057bc350 | 246 | RW |
1da177e4 LT |
247 | 1: PII/Celeron Diode |
248 | 2: 3904 transistor | |
249 | 3: thermal diode | |
b26f9330 | 250 | 4: thermistor |
61db011d RM |
251 | 5: AMD AMDSI |
252 | 6: Intel PECI | |
1da177e4 LT |
253 | Not all types are supported by all chips |
254 | ||
057bc350 | 255 | temp[1-*]_max Temperature max value. |
740e06a8 | 256 | Unit: millidegree Celsius (or millivolt, see below) |
057bc350 | 257 | RW |
1da177e4 | 258 | |
057bc350 | 259 | temp[1-*]_min Temperature min value. |
740e06a8 | 260 | Unit: millidegree Celsius |
057bc350 | 261 | RW |
1da177e4 | 262 | |
057bc350 | 263 | temp[1-*]_max_hyst |
1da177e4 | 264 | Temperature hysteresis value for max limit. |
740e06a8 | 265 | Unit: millidegree Celsius |
1da177e4 LT |
266 | Must be reported as an absolute temperature, NOT a delta |
267 | from the max value. | |
057bc350 | 268 | RW |
1da177e4 | 269 | |
057bc350 | 270 | temp[1-*]_input Temperature input value. |
740e06a8 | 271 | Unit: millidegree Celsius |
057bc350 | 272 | RO |
1da177e4 | 273 | |
057bc350 | 274 | temp[1-*]_crit Temperature critical value, typically greater than |
1da177e4 | 275 | corresponding temp_max values. |
740e06a8 | 276 | Unit: millidegree Celsius |
057bc350 | 277 | RW |
1da177e4 | 278 | |
057bc350 | 279 | temp[1-*]_crit_hyst |
1da177e4 | 280 | Temperature hysteresis value for critical limit. |
740e06a8 | 281 | Unit: millidegree Celsius |
1da177e4 LT |
282 | Must be reported as an absolute temperature, NOT a delta |
283 | from the critical value. | |
057bc350 | 284 | RW |
1da177e4 | 285 | |
176544dc | 286 | temp[1-*]_offset |
59ac8367 HR |
287 | Temperature offset which is added to the temperature reading |
288 | by the chip. | |
289 | Unit: millidegree Celsius | |
290 | Read/Write value. | |
291 | ||
176544dc JD |
292 | temp[1-*]_label Suggested temperature channel label. |
293 | Text string | |
294 | Should only be created if the driver has hints about what | |
295 | this temperature channel is being used for, and user-space | |
296 | doesn't. In all other cases, the label is provided by | |
297 | user-space. | |
298 | RO | |
1da177e4 | 299 | |
740e06a8 JD |
300 | Some chips measure temperature using external thermistors and an ADC, and |
301 | report the temperature measurement as a voltage. Converting this voltage | |
302 | back to a temperature (or the other way around for limits) requires | |
303 | mathematical functions not available in the kernel, so the conversion | |
304 | must occur in user space. For these chips, all temp* files described | |
305 | above should contain values expressed in millivolt instead of millidegree | |
306 | Celsius. In other words, such temperature channels are handled as voltage | |
307 | channels by the driver. | |
308 | ||
057bc350 RM |
309 | Also see the Alarms section for status flags associated with temperatures. |
310 | ||
1da177e4 LT |
311 | |
312 | ************ | |
313 | * Currents * | |
314 | ************ | |
315 | ||
316 | Note that no known chip provides current measurements as of writing, | |
317 | so this part is theoretical, so to say. | |
318 | ||
057bc350 | 319 | curr[1-*]_max Current max value |
1da177e4 | 320 | Unit: milliampere |
057bc350 | 321 | RW |
1da177e4 | 322 | |
057bc350 | 323 | curr[1-*]_min Current min value. |
1da177e4 | 324 | Unit: milliampere |
057bc350 | 325 | RW |
1da177e4 | 326 | |
057bc350 | 327 | curr[1-*]_input Current input value |
1da177e4 | 328 | Unit: milliampere |
057bc350 | 329 | RO |
1da177e4 | 330 | |
38fb56a2 DW |
331 | ********* |
332 | * Power * | |
333 | ********* | |
334 | ||
335 | power[1-*]_average Average power use | |
336 | Unit: microWatt | |
337 | RO | |
338 | ||
339 | power[1-*]_average_highest Historical average maximum power use | |
340 | Unit: microWatt | |
341 | RO | |
342 | ||
343 | power[1-*]_average_lowest Historical average minimum power use | |
344 | Unit: microWatt | |
345 | RO | |
346 | ||
347 | power[1-*]_input Instantaneous power use | |
348 | Unit: microWatt | |
349 | RO | |
350 | ||
351 | power[1-*]_input_highest Historical maximum power use | |
352 | Unit: microWatt | |
353 | RO | |
354 | ||
355 | power[1-*]_input_lowest Historical minimum power use | |
356 | Unit: microWatt | |
357 | RO | |
358 | ||
359 | power[1-*]_reset_history Reset input_highest, input_lowest, | |
360 | average_highest and average_lowest. | |
361 | WO | |
1da177e4 | 362 | |
400b48ec JD |
363 | ********** |
364 | * Alarms * | |
365 | ********** | |
366 | ||
367 | Each channel or limit may have an associated alarm file, containing a | |
368 | boolean value. 1 means than an alarm condition exists, 0 means no alarm. | |
369 | ||
370 | Usually a given chip will either use channel-related alarms, or | |
371 | limit-related alarms, not both. The driver should just reflect the hardware | |
372 | implementation. | |
373 | ||
057bc350 RM |
374 | in[0-*]_alarm |
375 | fan[1-*]_alarm | |
376 | temp[1-*]_alarm | |
400b48ec | 377 | Channel alarm |
057bc350 RM |
378 | 0: no alarm |
379 | 1: alarm | |
380 | RO | |
400b48ec JD |
381 | |
382 | OR | |
383 | ||
057bc350 RM |
384 | in[0-*]_min_alarm |
385 | in[0-*]_max_alarm | |
386 | fan[1-*]_min_alarm | |
387 | temp[1-*]_min_alarm | |
388 | temp[1-*]_max_alarm | |
389 | temp[1-*]_crit_alarm | |
400b48ec | 390 | Limit alarm |
057bc350 RM |
391 | 0: no alarm |
392 | 1: alarm | |
393 | RO | |
400b48ec JD |
394 | |
395 | Each input channel may have an associated fault file. This can be used | |
396 | to notify open diodes, unconnected fans etc. where the hardware | |
397 | supports it. When this boolean has value 1, the measurement for that | |
398 | channel should not be trusted. | |
399 | ||
7817a39e JD |
400 | in[0-*]_fault |
401 | fan[1-*]_fault | |
402 | temp[1-*]_fault | |
400b48ec | 403 | Input fault condition |
057bc350 RM |
404 | 0: no fault occured |
405 | 1: fault condition | |
406 | RO | |
400b48ec JD |
407 | |
408 | Some chips also offer the possibility to get beeped when an alarm occurs: | |
409 | ||
410 | beep_enable Master beep enable | |
057bc350 RM |
411 | 0: no beeps |
412 | 1: beeps | |
413 | RW | |
400b48ec | 414 | |
057bc350 RM |
415 | in[0-*]_beep |
416 | fan[1-*]_beep | |
417 | temp[1-*]_beep | |
400b48ec | 418 | Channel beep |
057bc350 RM |
419 | 0: disable |
420 | 1: enable | |
421 | RW | |
400b48ec JD |
422 | |
423 | In theory, a chip could provide per-limit beep masking, but no such chip | |
424 | was seen so far. | |
425 | ||
426 | Old drivers provided a different, non-standard interface to alarms and | |
427 | beeps. These interface files are deprecated, but will be kept around | |
428 | for compatibility reasons: | |
1da177e4 LT |
429 | |
430 | alarms Alarm bitmask. | |
057bc350 | 431 | RO |
1da177e4 LT |
432 | Integer representation of one to four bytes. |
433 | A '1' bit means an alarm. | |
434 | Chips should be programmed for 'comparator' mode so that | |
435 | the alarm will 'come back' after you read the register | |
436 | if it is still valid. | |
437 | Generally a direct representation of a chip's internal | |
438 | alarm registers; there is no standard for the position | |
400b48ec JD |
439 | of individual bits. For this reason, the use of this |
440 | interface file for new drivers is discouraged. Use | |
441 | individual *_alarm and *_fault files instead. | |
1da177e4 LT |
442 | Bits are defined in kernel/include/sensors.h. |
443 | ||
1da177e4 | 444 | beep_mask Bitmask for beep. |
400b48ec JD |
445 | Same format as 'alarms' with the same bit locations, |
446 | use discouraged for the same reason. Use individual | |
447 | *_beep files instead. | |
057bc350 | 448 | RW |
2ed42633 HG |
449 | |
450 | ||
451 | sysfs attribute writes interpretation | |
452 | ------------------------------------- | |
453 | ||
454 | hwmon sysfs attributes always contain numbers, so the first thing to do is to | |
455 | convert the input to a number, there are 2 ways todo this depending whether | |
456 | the number can be negative or not: | |
457 | unsigned long u = simple_strtoul(buf, NULL, 10); | |
458 | long s = simple_strtol(buf, NULL, 10); | |
459 | ||
460 | With buf being the buffer with the user input being passed by the kernel. | |
461 | Notice that we do not use the second argument of strto[u]l, and thus cannot | |
462 | tell when 0 is returned, if this was really 0 or is caused by invalid input. | |
463 | This is done deliberately as checking this everywhere would add a lot of | |
464 | code to the kernel. | |
465 | ||
466 | Notice that it is important to always store the converted value in an | |
467 | unsigned long or long, so that no wrap around can happen before any further | |
468 | checking. | |
469 | ||
470 | After the input string is converted to an (unsigned) long, the value should be | |
471 | checked if its acceptable. Be careful with further conversions on the value | |
472 | before checking it for validity, as these conversions could still cause a wrap | |
473 | around before the check. For example do not multiply the result, and only | |
474 | add/subtract if it has been divided before the add/subtract. | |
475 | ||
476 | What to do if a value is found to be invalid, depends on the type of the | |
477 | sysfs attribute that is being set. If it is a continuous setting like a | |
478 | tempX_max or inX_max attribute, then the value should be clamped to its | |
479 | limits using SENSORS_LIMIT(value, min_limit, max_limit). If it is not | |
480 | continuous like for example a tempX_type, then when an invalid value is | |
481 | written, -EINVAL should be returned. | |
482 | ||
483 | Example1, temp1_max, register is a signed 8 bit value (-128 - 127 degrees): | |
5fbea518 JD |
484 | |
485 | long v = simple_strtol(buf, NULL, 10) / 1000; | |
486 | v = SENSORS_LIMIT(v, -128, 127); | |
487 | /* write v to register */ | |
2ed42633 HG |
488 | |
489 | Example2, fan divider setting, valid values 2, 4 and 8: | |
5fbea518 JD |
490 | |
491 | unsigned long v = simple_strtoul(buf, NULL, 10); | |
492 | ||
493 | switch (v) { | |
494 | case 2: v = 1; break; | |
495 | case 4: v = 2; break; | |
496 | case 8: v = 3; break; | |
497 | default: | |
498 | return -EINVAL; | |
499 | } | |
500 | /* write v to register */ |