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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 |
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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 | |
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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. | |
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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. |
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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 | ||
70 | ||
71 | ------------------------------------------------------------------------- | |
72 | ||
057bc350 RM |
73 | [0-*] denotes any positive number starting from 0 |
74 | [1-*] denotes any positive number starting from 1 | |
75 | RO read only value | |
76 | RW read/write value | |
77 | ||
78 | Read/write values may be read-only for some chips, depending on the | |
79 | hardware implementation. | |
80 | ||
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81 | All entries are optional, and should only be created in a given driver |
82 | if the chip has the feature. | |
83 | ||
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84 | ************ |
85 | * Voltages * | |
86 | ************ | |
87 | ||
057bc350 | 88 | in[0-*]_min Voltage min value. |
1da177e4 | 89 | Unit: millivolt |
057bc350 | 90 | RW |
1da177e4 | 91 | |
057bc350 | 92 | in[0-*]_max Voltage max value. |
1da177e4 | 93 | Unit: millivolt |
057bc350 | 94 | RW |
1da177e4 | 95 | |
057bc350 | 96 | in[0-*]_input Voltage input value. |
1da177e4 | 97 | Unit: millivolt |
057bc350 RM |
98 | RO |
99 | Voltage measured on the chip pin. | |
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100 | Actual voltage depends on the scaling resistors on the |
101 | motherboard, as recommended in the chip datasheet. | |
102 | This varies by chip and by motherboard. | |
103 | Because of this variation, values are generally NOT scaled | |
104 | by the chip driver, and must be done by the application. | |
105 | However, some drivers (notably lm87 and via686a) | |
057bc350 | 106 | do scale, because of internal resistors built into a chip. |
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107 | These drivers will output the actual voltage. |
108 | ||
109 | Typical usage: | |
110 | in0_* CPU #1 voltage (not scaled) | |
111 | in1_* CPU #2 voltage (not scaled) | |
112 | in2_* 3.3V nominal (not scaled) | |
113 | in3_* 5.0V nominal (scaled) | |
114 | in4_* 12.0V nominal (scaled) | |
115 | in5_* -12.0V nominal (scaled) | |
116 | in6_* -5.0V nominal (scaled) | |
117 | in7_* varies | |
118 | in8_* varies | |
119 | ||
057bc350 | 120 | cpu[0-*]_vid CPU core reference voltage. |
1da177e4 | 121 | Unit: millivolt |
057bc350 | 122 | RO |
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123 | Not always correct. |
124 | ||
125 | vrm Voltage Regulator Module version number. | |
057bc350 RM |
126 | RW (but changing it should no more be necessary) |
127 | Originally the VRM standard version multiplied by 10, but now | |
128 | an arbitrary number, as not all standards have a version | |
129 | number. | |
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130 | Affects the way the driver calculates the CPU core reference |
131 | voltage from the vid pins. | |
132 | ||
057bc350 RM |
133 | Also see the Alarms section for status flags associated with voltages. |
134 | ||
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135 | |
136 | ******** | |
137 | * Fans * | |
138 | ******** | |
139 | ||
057bc350 | 140 | fan[1-*]_min Fan minimum value |
1da177e4 | 141 | Unit: revolution/min (RPM) |
057bc350 | 142 | RW |
1da177e4 | 143 | |
057bc350 | 144 | fan[1-*]_input Fan input value. |
1da177e4 | 145 | Unit: revolution/min (RPM) |
057bc350 | 146 | RO |
1da177e4 | 147 | |
057bc350 | 148 | fan[1-*]_div Fan divisor. |
1da177e4 | 149 | Integer value in powers of two (1, 2, 4, 8, 16, 32, 64, 128). |
057bc350 | 150 | RW |
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151 | Some chips only support values 1, 2, 4 and 8. |
152 | Note that this is actually an internal clock divisor, which | |
153 | affects the measurable speed range, not the read value. | |
154 | ||
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155 | fan[1-*]_target |
156 | Desired fan speed | |
157 | Unit: revolution/min (RPM) | |
158 | RW | |
159 | Only makes sense if the chip supports closed-loop fan speed | |
160 | control based on the measured fan speed. | |
161 | ||
057bc350 RM |
162 | Also see the Alarms section for status flags associated with fans. |
163 | ||
164 | ||
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165 | ******* |
166 | * PWM * | |
167 | ******* | |
168 | ||
057bc350 | 169 | pwm[1-*] Pulse width modulation fan control. |
1da177e4 | 170 | Integer value in the range 0 to 255 |
057bc350 | 171 | RW |
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172 | 255 is max or 100%. |
173 | ||
057bc350 | 174 | pwm[1-*]_enable |
1da177e4 | 175 | Switch PWM on and off. |
f8d0c19a | 176 | Not always present even if pwmN is. |
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177 | 0: turn off |
178 | 1: turn on in manual mode | |
179 | 2+: turn on in automatic mode | |
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180 | Check individual chip documentation files for automatic mode |
181 | details. | |
057bc350 RM |
182 | RW |
183 | ||
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184 | pwm[1-*]_mode 0: DC mode (direct current) |
185 | 1: PWM mode (pulse-width modulation) | |
186 | RW | |
187 | ||
188 | pwm[1-*]_freq Base PWM frequency in Hz. | |
189 | Only possibly available when pwmN_mode is PWM, but not always | |
190 | present even then. | |
057bc350 | 191 | RW |
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192 | |
193 | pwm[1-*]_auto_channels_temp | |
194 | Select which temperature channels affect this PWM output in | |
195 | auto mode. Bitfield, 1 is temp1, 2 is temp2, 4 is temp3 etc... | |
196 | Which values are possible depend on the chip used. | |
057bc350 | 197 | RW |
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198 | |
199 | pwm[1-*]_auto_point[1-*]_pwm | |
200 | pwm[1-*]_auto_point[1-*]_temp | |
201 | pwm[1-*]_auto_point[1-*]_temp_hyst | |
202 | Define the PWM vs temperature curve. Number of trip points is | |
203 | chip-dependent. Use this for chips which associate trip points | |
204 | to PWM output channels. | |
057bc350 | 205 | RW |
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206 | |
207 | OR | |
208 | ||
209 | temp[1-*]_auto_point[1-*]_pwm | |
210 | temp[1-*]_auto_point[1-*]_temp | |
211 | temp[1-*]_auto_point[1-*]_temp_hyst | |
212 | Define the PWM vs temperature curve. Number of trip points is | |
213 | chip-dependent. Use this for chips which associate trip points | |
214 | to temperature channels. | |
057bc350 | 215 | RW |
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216 | |
217 | ||
218 | **************** | |
219 | * Temperatures * | |
220 | **************** | |
221 | ||
057bc350 | 222 | temp[1-*]_type Sensor type selection. |
61db011d | 223 | Integers 1 to 6 or thermistor Beta value (typically 3435) |
057bc350 | 224 | RW |
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225 | 1: PII/Celeron Diode |
226 | 2: 3904 transistor | |
227 | 3: thermal diode | |
e53004e2 | 228 | 4: thermistor (default/unknown Beta) |
61db011d RM |
229 | 5: AMD AMDSI |
230 | 6: Intel PECI | |
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231 | Not all types are supported by all chips |
232 | ||
057bc350 | 233 | temp[1-*]_max Temperature max value. |
740e06a8 | 234 | Unit: millidegree Celsius (or millivolt, see below) |
057bc350 | 235 | RW |
1da177e4 | 236 | |
057bc350 | 237 | temp[1-*]_min Temperature min value. |
740e06a8 | 238 | Unit: millidegree Celsius |
057bc350 | 239 | RW |
1da177e4 | 240 | |
057bc350 | 241 | temp[1-*]_max_hyst |
1da177e4 | 242 | Temperature hysteresis value for max limit. |
740e06a8 | 243 | Unit: millidegree Celsius |
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244 | Must be reported as an absolute temperature, NOT a delta |
245 | from the max value. | |
057bc350 | 246 | RW |
1da177e4 | 247 | |
057bc350 | 248 | temp[1-*]_input Temperature input value. |
740e06a8 | 249 | Unit: millidegree Celsius |
057bc350 | 250 | RO |
1da177e4 | 251 | |
057bc350 | 252 | temp[1-*]_crit Temperature critical value, typically greater than |
1da177e4 | 253 | corresponding temp_max values. |
740e06a8 | 254 | Unit: millidegree Celsius |
057bc350 | 255 | RW |
1da177e4 | 256 | |
057bc350 | 257 | temp[1-*]_crit_hyst |
1da177e4 | 258 | Temperature hysteresis value for critical limit. |
740e06a8 | 259 | Unit: millidegree Celsius |
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260 | Must be reported as an absolute temperature, NOT a delta |
261 | from the critical value. | |
057bc350 | 262 | RW |
1da177e4 | 263 | |
59ac8367 HR |
264 | temp[1-4]_offset |
265 | Temperature offset which is added to the temperature reading | |
266 | by the chip. | |
267 | Unit: millidegree Celsius | |
268 | Read/Write value. | |
269 | ||
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270 | If there are multiple temperature sensors, temp1_* is |
271 | generally the sensor inside the chip itself, | |
272 | reported as "motherboard temperature". temp2_* to | |
273 | temp4_* are generally sensors external to the chip | |
274 | itself, for example the thermal diode inside the CPU or | |
275 | a thermistor nearby. | |
276 | ||
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277 | Some chips measure temperature using external thermistors and an ADC, and |
278 | report the temperature measurement as a voltage. Converting this voltage | |
279 | back to a temperature (or the other way around for limits) requires | |
280 | mathematical functions not available in the kernel, so the conversion | |
281 | must occur in user space. For these chips, all temp* files described | |
282 | above should contain values expressed in millivolt instead of millidegree | |
283 | Celsius. In other words, such temperature channels are handled as voltage | |
284 | channels by the driver. | |
285 | ||
057bc350 RM |
286 | Also see the Alarms section for status flags associated with temperatures. |
287 | ||
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288 | |
289 | ************ | |
290 | * Currents * | |
291 | ************ | |
292 | ||
293 | Note that no known chip provides current measurements as of writing, | |
294 | so this part is theoretical, so to say. | |
295 | ||
057bc350 | 296 | curr[1-*]_max Current max value |
1da177e4 | 297 | Unit: milliampere |
057bc350 | 298 | RW |
1da177e4 | 299 | |
057bc350 | 300 | curr[1-*]_min Current min value. |
1da177e4 | 301 | Unit: milliampere |
057bc350 | 302 | RW |
1da177e4 | 303 | |
057bc350 | 304 | curr[1-*]_input Current input value |
1da177e4 | 305 | Unit: milliampere |
057bc350 | 306 | RO |
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307 | |
308 | ||
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309 | ********** |
310 | * Alarms * | |
311 | ********** | |
312 | ||
313 | Each channel or limit may have an associated alarm file, containing a | |
314 | boolean value. 1 means than an alarm condition exists, 0 means no alarm. | |
315 | ||
316 | Usually a given chip will either use channel-related alarms, or | |
317 | limit-related alarms, not both. The driver should just reflect the hardware | |
318 | implementation. | |
319 | ||
057bc350 RM |
320 | in[0-*]_alarm |
321 | fan[1-*]_alarm | |
322 | temp[1-*]_alarm | |
400b48ec | 323 | Channel alarm |
057bc350 RM |
324 | 0: no alarm |
325 | 1: alarm | |
326 | RO | |
400b48ec JD |
327 | |
328 | OR | |
329 | ||
057bc350 RM |
330 | in[0-*]_min_alarm |
331 | in[0-*]_max_alarm | |
332 | fan[1-*]_min_alarm | |
333 | temp[1-*]_min_alarm | |
334 | temp[1-*]_max_alarm | |
335 | temp[1-*]_crit_alarm | |
400b48ec | 336 | Limit alarm |
057bc350 RM |
337 | 0: no alarm |
338 | 1: alarm | |
339 | RO | |
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340 | |
341 | Each input channel may have an associated fault file. This can be used | |
342 | to notify open diodes, unconnected fans etc. where the hardware | |
343 | supports it. When this boolean has value 1, the measurement for that | |
344 | channel should not be trusted. | |
345 | ||
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346 | in[0-*]_fault |
347 | fan[1-*]_fault | |
348 | temp[1-*]_fault | |
400b48ec | 349 | Input fault condition |
057bc350 RM |
350 | 0: no fault occured |
351 | 1: fault condition | |
352 | RO | |
400b48ec JD |
353 | |
354 | Some chips also offer the possibility to get beeped when an alarm occurs: | |
355 | ||
356 | beep_enable Master beep enable | |
057bc350 RM |
357 | 0: no beeps |
358 | 1: beeps | |
359 | RW | |
400b48ec | 360 | |
057bc350 RM |
361 | in[0-*]_beep |
362 | fan[1-*]_beep | |
363 | temp[1-*]_beep | |
400b48ec | 364 | Channel beep |
057bc350 RM |
365 | 0: disable |
366 | 1: enable | |
367 | RW | |
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368 | |
369 | In theory, a chip could provide per-limit beep masking, but no such chip | |
370 | was seen so far. | |
371 | ||
372 | Old drivers provided a different, non-standard interface to alarms and | |
373 | beeps. These interface files are deprecated, but will be kept around | |
374 | for compatibility reasons: | |
1da177e4 LT |
375 | |
376 | alarms Alarm bitmask. | |
057bc350 | 377 | RO |
1da177e4 LT |
378 | Integer representation of one to four bytes. |
379 | A '1' bit means an alarm. | |
380 | Chips should be programmed for 'comparator' mode so that | |
381 | the alarm will 'come back' after you read the register | |
382 | if it is still valid. | |
383 | Generally a direct representation of a chip's internal | |
384 | alarm registers; there is no standard for the position | |
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385 | of individual bits. For this reason, the use of this |
386 | interface file for new drivers is discouraged. Use | |
387 | individual *_alarm and *_fault files instead. | |
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388 | Bits are defined in kernel/include/sensors.h. |
389 | ||
1da177e4 | 390 | beep_mask Bitmask for beep. |
400b48ec JD |
391 | Same format as 'alarms' with the same bit locations, |
392 | use discouraged for the same reason. Use individual | |
393 | *_beep files instead. | |
057bc350 | 394 | RW |
1da177e4 | 395 | |
400b48ec JD |
396 | |
397 | ********* | |
398 | * Other * | |
399 | ********* | |
400 | ||
1da177e4 | 401 | eeprom Raw EEPROM data in binary form. |
057bc350 | 402 | RO |
c3df5806 JD |
403 | |
404 | pec Enable or disable PEC (SMBus only) | |
057bc350 RM |
405 | 0: disable |
406 | 1: enable | |
407 | RW |