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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 | ||
176544dc JD |
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 | * Name * | |
87 | ******** | |
88 | ||
89 | name The chip name. | |
90 | This should be a short, lowercase string, not containing | |
91 | spaces nor dashes, representing the chip name. This is | |
92 | the only mandatory attribute. | |
93 | I2C devices get this attribute created automatically. | |
94 | RO | |
95 | ||
740e06a8 | 96 | |
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97 | ************ |
98 | * Voltages * | |
99 | ************ | |
100 | ||
057bc350 | 101 | in[0-*]_min Voltage min value. |
1da177e4 | 102 | Unit: millivolt |
057bc350 | 103 | RW |
1da177e4 | 104 | |
057bc350 | 105 | in[0-*]_max Voltage max value. |
1da177e4 | 106 | Unit: millivolt |
057bc350 | 107 | RW |
1da177e4 | 108 | |
057bc350 | 109 | in[0-*]_input Voltage input value. |
1da177e4 | 110 | Unit: millivolt |
057bc350 RM |
111 | RO |
112 | Voltage measured on the chip pin. | |
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113 | Actual voltage depends on the scaling resistors on the |
114 | motherboard, as recommended in the chip datasheet. | |
115 | This varies by chip and by motherboard. | |
116 | Because of this variation, values are generally NOT scaled | |
117 | by the chip driver, and must be done by the application. | |
118 | However, some drivers (notably lm87 and via686a) | |
057bc350 | 119 | do scale, because of internal resistors built into a chip. |
176544dc JD |
120 | These drivers will output the actual voltage. Rule of |
121 | thumb: drivers should report the voltage values at the | |
122 | "pins" of the chip. | |
123 | ||
124 | in[0-*]_label Suggested voltage channel label. | |
125 | Text string | |
126 | Should only be created if the driver has hints about what | |
127 | this voltage channel is being used for, and user-space | |
128 | doesn't. In all other cases, the label is provided by | |
129 | user-space. | |
130 | RO | |
1da177e4 | 131 | |
057bc350 | 132 | cpu[0-*]_vid CPU core reference voltage. |
1da177e4 | 133 | Unit: millivolt |
057bc350 | 134 | RO |
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135 | Not always correct. |
136 | ||
137 | vrm Voltage Regulator Module version number. | |
057bc350 RM |
138 | RW (but changing it should no more be necessary) |
139 | Originally the VRM standard version multiplied by 10, but now | |
140 | an arbitrary number, as not all standards have a version | |
141 | number. | |
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142 | Affects the way the driver calculates the CPU core reference |
143 | voltage from the vid pins. | |
144 | ||
057bc350 RM |
145 | Also see the Alarms section for status flags associated with voltages. |
146 | ||
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147 | |
148 | ******** | |
149 | * Fans * | |
150 | ******** | |
151 | ||
057bc350 | 152 | fan[1-*]_min Fan minimum value |
1da177e4 | 153 | Unit: revolution/min (RPM) |
057bc350 | 154 | RW |
1da177e4 | 155 | |
057bc350 | 156 | fan[1-*]_input Fan input value. |
1da177e4 | 157 | Unit: revolution/min (RPM) |
057bc350 | 158 | RO |
1da177e4 | 159 | |
057bc350 | 160 | fan[1-*]_div Fan divisor. |
1da177e4 | 161 | Integer value in powers of two (1, 2, 4, 8, 16, 32, 64, 128). |
057bc350 | 162 | RW |
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163 | Some chips only support values 1, 2, 4 and 8. |
164 | Note that this is actually an internal clock divisor, which | |
165 | affects the measurable speed range, not the read value. | |
166 | ||
2dbc514a JD |
167 | fan[1-*]_target |
168 | Desired fan speed | |
169 | Unit: revolution/min (RPM) | |
170 | RW | |
171 | Only makes sense if the chip supports closed-loop fan speed | |
172 | control based on the measured fan speed. | |
173 | ||
176544dc JD |
174 | fan[1-*]_label Suggested fan channel label. |
175 | Text string | |
176 | Should only be created if the driver has hints about what | |
177 | this fan channel is being used for, and user-space doesn't. | |
178 | In all other cases, the label is provided by user-space. | |
179 | RO | |
180 | ||
057bc350 RM |
181 | Also see the Alarms section for status flags associated with fans. |
182 | ||
183 | ||
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184 | ******* |
185 | * PWM * | |
186 | ******* | |
187 | ||
057bc350 | 188 | pwm[1-*] Pulse width modulation fan control. |
1da177e4 | 189 | Integer value in the range 0 to 255 |
057bc350 | 190 | RW |
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191 | 255 is max or 100%. |
192 | ||
057bc350 | 193 | pwm[1-*]_enable |
875f25d5 JD |
194 | Fan speed control method: |
195 | 0: no fan speed control (i.e. fan at full speed) | |
196 | 1: manual fan speed control enabled (using pwm[1-*]) | |
197 | 2+: automatic fan speed control enabled | |
f8d0c19a JD |
198 | Check individual chip documentation files for automatic mode |
199 | details. | |
057bc350 RM |
200 | RW |
201 | ||
f8d0c19a JD |
202 | pwm[1-*]_mode 0: DC mode (direct current) |
203 | 1: PWM mode (pulse-width modulation) | |
204 | RW | |
205 | ||
206 | pwm[1-*]_freq Base PWM frequency in Hz. | |
207 | Only possibly available when pwmN_mode is PWM, but not always | |
208 | present even then. | |
057bc350 | 209 | RW |
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210 | |
211 | pwm[1-*]_auto_channels_temp | |
212 | Select which temperature channels affect this PWM output in | |
213 | auto mode. Bitfield, 1 is temp1, 2 is temp2, 4 is temp3 etc... | |
214 | Which values are possible depend on the chip used. | |
057bc350 | 215 | RW |
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216 | |
217 | pwm[1-*]_auto_point[1-*]_pwm | |
218 | pwm[1-*]_auto_point[1-*]_temp | |
219 | pwm[1-*]_auto_point[1-*]_temp_hyst | |
220 | Define the PWM vs temperature curve. Number of trip points is | |
221 | chip-dependent. Use this for chips which associate trip points | |
222 | to PWM output channels. | |
057bc350 | 223 | RW |
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224 | |
225 | OR | |
226 | ||
227 | temp[1-*]_auto_point[1-*]_pwm | |
228 | temp[1-*]_auto_point[1-*]_temp | |
229 | temp[1-*]_auto_point[1-*]_temp_hyst | |
230 | Define the PWM vs temperature curve. Number of trip points is | |
231 | chip-dependent. Use this for chips which associate trip points | |
232 | to temperature channels. | |
057bc350 | 233 | RW |
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234 | |
235 | ||
236 | **************** | |
237 | * Temperatures * | |
238 | **************** | |
239 | ||
057bc350 | 240 | temp[1-*]_type Sensor type selection. |
b26f9330 | 241 | Integers 1 to 6 |
057bc350 | 242 | RW |
1da177e4 LT |
243 | 1: PII/Celeron Diode |
244 | 2: 3904 transistor | |
245 | 3: thermal diode | |
b26f9330 | 246 | 4: thermistor |
61db011d RM |
247 | 5: AMD AMDSI |
248 | 6: Intel PECI | |
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249 | Not all types are supported by all chips |
250 | ||
057bc350 | 251 | temp[1-*]_max Temperature max value. |
740e06a8 | 252 | Unit: millidegree Celsius (or millivolt, see below) |
057bc350 | 253 | RW |
1da177e4 | 254 | |
057bc350 | 255 | temp[1-*]_min Temperature min value. |
740e06a8 | 256 | Unit: millidegree Celsius |
057bc350 | 257 | RW |
1da177e4 | 258 | |
057bc350 | 259 | temp[1-*]_max_hyst |
1da177e4 | 260 | Temperature hysteresis value for max limit. |
740e06a8 | 261 | Unit: millidegree Celsius |
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262 | Must be reported as an absolute temperature, NOT a delta |
263 | from the max value. | |
057bc350 | 264 | RW |
1da177e4 | 265 | |
057bc350 | 266 | temp[1-*]_input Temperature input value. |
740e06a8 | 267 | Unit: millidegree Celsius |
057bc350 | 268 | RO |
1da177e4 | 269 | |
057bc350 | 270 | temp[1-*]_crit Temperature critical value, typically greater than |
1da177e4 | 271 | corresponding temp_max values. |
740e06a8 | 272 | Unit: millidegree Celsius |
057bc350 | 273 | RW |
1da177e4 | 274 | |
057bc350 | 275 | temp[1-*]_crit_hyst |
1da177e4 | 276 | Temperature hysteresis value for critical limit. |
740e06a8 | 277 | Unit: millidegree Celsius |
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278 | Must be reported as an absolute temperature, NOT a delta |
279 | from the critical value. | |
057bc350 | 280 | RW |
1da177e4 | 281 | |
176544dc | 282 | temp[1-*]_offset |
59ac8367 HR |
283 | Temperature offset which is added to the temperature reading |
284 | by the chip. | |
285 | Unit: millidegree Celsius | |
286 | Read/Write value. | |
287 | ||
176544dc JD |
288 | temp[1-*]_label Suggested temperature channel label. |
289 | Text string | |
290 | Should only be created if the driver has hints about what | |
291 | this temperature channel is being used for, and user-space | |
292 | doesn't. In all other cases, the label is provided by | |
293 | user-space. | |
294 | RO | |
1da177e4 | 295 | |
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296 | Some chips measure temperature using external thermistors and an ADC, and |
297 | report the temperature measurement as a voltage. Converting this voltage | |
298 | back to a temperature (or the other way around for limits) requires | |
299 | mathematical functions not available in the kernel, so the conversion | |
300 | must occur in user space. For these chips, all temp* files described | |
301 | above should contain values expressed in millivolt instead of millidegree | |
302 | Celsius. In other words, such temperature channels are handled as voltage | |
303 | channels by the driver. | |
304 | ||
057bc350 RM |
305 | Also see the Alarms section for status flags associated with temperatures. |
306 | ||
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307 | |
308 | ************ | |
309 | * Currents * | |
310 | ************ | |
311 | ||
312 | Note that no known chip provides current measurements as of writing, | |
313 | so this part is theoretical, so to say. | |
314 | ||
057bc350 | 315 | curr[1-*]_max Current max value |
1da177e4 | 316 | Unit: milliampere |
057bc350 | 317 | RW |
1da177e4 | 318 | |
057bc350 | 319 | curr[1-*]_min Current min value. |
1da177e4 | 320 | Unit: milliampere |
057bc350 | 321 | RW |
1da177e4 | 322 | |
057bc350 | 323 | curr[1-*]_input Current input value |
1da177e4 | 324 | Unit: milliampere |
057bc350 | 325 | RO |
1da177e4 LT |
326 | |
327 | ||
400b48ec JD |
328 | ********** |
329 | * Alarms * | |
330 | ********** | |
331 | ||
332 | Each channel or limit may have an associated alarm file, containing a | |
333 | boolean value. 1 means than an alarm condition exists, 0 means no alarm. | |
334 | ||
335 | Usually a given chip will either use channel-related alarms, or | |
336 | limit-related alarms, not both. The driver should just reflect the hardware | |
337 | implementation. | |
338 | ||
057bc350 RM |
339 | in[0-*]_alarm |
340 | fan[1-*]_alarm | |
341 | temp[1-*]_alarm | |
400b48ec | 342 | Channel alarm |
057bc350 RM |
343 | 0: no alarm |
344 | 1: alarm | |
345 | RO | |
400b48ec JD |
346 | |
347 | OR | |
348 | ||
057bc350 RM |
349 | in[0-*]_min_alarm |
350 | in[0-*]_max_alarm | |
351 | fan[1-*]_min_alarm | |
352 | temp[1-*]_min_alarm | |
353 | temp[1-*]_max_alarm | |
354 | temp[1-*]_crit_alarm | |
400b48ec | 355 | Limit alarm |
057bc350 RM |
356 | 0: no alarm |
357 | 1: alarm | |
358 | RO | |
400b48ec JD |
359 | |
360 | Each input channel may have an associated fault file. This can be used | |
361 | to notify open diodes, unconnected fans etc. where the hardware | |
362 | supports it. When this boolean has value 1, the measurement for that | |
363 | channel should not be trusted. | |
364 | ||
7817a39e JD |
365 | in[0-*]_fault |
366 | fan[1-*]_fault | |
367 | temp[1-*]_fault | |
400b48ec | 368 | Input fault condition |
057bc350 RM |
369 | 0: no fault occured |
370 | 1: fault condition | |
371 | RO | |
400b48ec JD |
372 | |
373 | Some chips also offer the possibility to get beeped when an alarm occurs: | |
374 | ||
375 | beep_enable Master beep enable | |
057bc350 RM |
376 | 0: no beeps |
377 | 1: beeps | |
378 | RW | |
400b48ec | 379 | |
057bc350 RM |
380 | in[0-*]_beep |
381 | fan[1-*]_beep | |
382 | temp[1-*]_beep | |
400b48ec | 383 | Channel beep |
057bc350 RM |
384 | 0: disable |
385 | 1: enable | |
386 | RW | |
400b48ec JD |
387 | |
388 | In theory, a chip could provide per-limit beep masking, but no such chip | |
389 | was seen so far. | |
390 | ||
391 | Old drivers provided a different, non-standard interface to alarms and | |
392 | beeps. These interface files are deprecated, but will be kept around | |
393 | for compatibility reasons: | |
1da177e4 LT |
394 | |
395 | alarms Alarm bitmask. | |
057bc350 | 396 | RO |
1da177e4 LT |
397 | Integer representation of one to four bytes. |
398 | A '1' bit means an alarm. | |
399 | Chips should be programmed for 'comparator' mode so that | |
400 | the alarm will 'come back' after you read the register | |
401 | if it is still valid. | |
402 | Generally a direct representation of a chip's internal | |
403 | alarm registers; there is no standard for the position | |
400b48ec JD |
404 | of individual bits. For this reason, the use of this |
405 | interface file for new drivers is discouraged. Use | |
406 | individual *_alarm and *_fault files instead. | |
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407 | Bits are defined in kernel/include/sensors.h. |
408 | ||
1da177e4 | 409 | beep_mask Bitmask for beep. |
400b48ec JD |
410 | Same format as 'alarms' with the same bit locations, |
411 | use discouraged for the same reason. Use individual | |
412 | *_beep files instead. | |
057bc350 | 413 | RW |