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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 | |
6 | more further information. As of writing this document, libsensors | |
7 | (from lm_sensors 2.8.3) is heavily chip-dependant. Adding or updating | |
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 | ||
14 | The new sysfs interface was designed to be as chip-independant as | |
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 | ||
27 | For this reason, even if we aim at a chip-independant libsensors, it will | |
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 | |
42 | to changes, even important ones. One more reason to use the library instead | |
43 | of accessing sysfs files directly. | |
44 | ||
45 | Each chip gets its own directory in the sysfs /sys/devices tree. To | |
46 | find all sensor chips, it is easier to follow the symlinks from | |
47 | /sys/i2c/devices/ | |
48 | ||
49 | All sysfs values are fixed point numbers. To get the true value of some | |
50 | of the values, you should divide by the specified value. | |
51 | ||
52 | There is only one value per file, unlike the older /proc specification. | |
53 | The common scheme for files naming is: <type><number>_<item>. Usual | |
54 | types for sensor chips are "in" (voltage), "temp" (temperature) and | |
55 | "fan" (fan). Usual items are "input" (measured value), "max" (high | |
56 | threshold, "min" (low threshold). Numbering usually starts from 1, | |
57 | except for voltages which start from 0 (because most data sheets use | |
58 | this). A number is always used for elements that can be present more | |
59 | than once, even if there is a single element of the given type on the | |
60 | specific chip. Other files do not refer to a specific element, so | |
61 | they have a simple name, and no number. | |
62 | ||
63 | Alarms are direct indications read from the chips. The drivers do NOT | |
64 | make comparisons of readings to thresholds. This allows violations | |
65 | between readings to be caught and alarmed. The exact definition of an | |
66 | alarm (for example, whether a threshold must be met or must be exceeded | |
67 | to cause an alarm) is chip-dependent. | |
68 | ||
69 | ||
70 | ------------------------------------------------------------------------- | |
71 | ||
057bc350 RM |
72 | [0-*] denotes any positive number starting from 0 |
73 | [1-*] denotes any positive number starting from 1 | |
74 | RO read only value | |
75 | RW read/write value | |
76 | ||
77 | Read/write values may be read-only for some chips, depending on the | |
78 | hardware implementation. | |
79 | ||
1da177e4 LT |
80 | ************ |
81 | * Voltages * | |
82 | ************ | |
83 | ||
057bc350 | 84 | in[0-*]_min Voltage min value. |
1da177e4 | 85 | Unit: millivolt |
057bc350 | 86 | RW |
1da177e4 | 87 | |
057bc350 | 88 | in[0-*]_max Voltage max value. |
1da177e4 | 89 | Unit: millivolt |
057bc350 | 90 | RW |
1da177e4 | 91 | |
057bc350 | 92 | in[0-*]_input Voltage input value. |
1da177e4 | 93 | Unit: millivolt |
057bc350 RM |
94 | RO |
95 | Voltage measured on the chip pin. | |
1da177e4 LT |
96 | Actual voltage depends on the scaling resistors on the |
97 | motherboard, as recommended in the chip datasheet. | |
98 | This varies by chip and by motherboard. | |
99 | Because of this variation, values are generally NOT scaled | |
100 | by the chip driver, and must be done by the application. | |
101 | However, some drivers (notably lm87 and via686a) | |
057bc350 | 102 | do scale, because of internal resistors built into a chip. |
1da177e4 LT |
103 | These drivers will output the actual voltage. |
104 | ||
105 | Typical usage: | |
106 | in0_* CPU #1 voltage (not scaled) | |
107 | in1_* CPU #2 voltage (not scaled) | |
108 | in2_* 3.3V nominal (not scaled) | |
109 | in3_* 5.0V nominal (scaled) | |
110 | in4_* 12.0V nominal (scaled) | |
111 | in5_* -12.0V nominal (scaled) | |
112 | in6_* -5.0V nominal (scaled) | |
113 | in7_* varies | |
114 | in8_* varies | |
115 | ||
057bc350 | 116 | cpu[0-*]_vid CPU core reference voltage. |
1da177e4 | 117 | Unit: millivolt |
057bc350 | 118 | RO |
1da177e4 LT |
119 | Not always correct. |
120 | ||
121 | vrm Voltage Regulator Module version number. | |
057bc350 RM |
122 | RW (but changing it should no more be necessary) |
123 | Originally the VRM standard version multiplied by 10, but now | |
124 | an arbitrary number, as not all standards have a version | |
125 | number. | |
1da177e4 LT |
126 | Affects the way the driver calculates the CPU core reference |
127 | voltage from the vid pins. | |
128 | ||
057bc350 RM |
129 | Also see the Alarms section for status flags associated with voltages. |
130 | ||
1da177e4 LT |
131 | |
132 | ******** | |
133 | * Fans * | |
134 | ******** | |
135 | ||
057bc350 | 136 | fan[1-*]_min Fan minimum value |
1da177e4 | 137 | Unit: revolution/min (RPM) |
057bc350 | 138 | RW |
1da177e4 | 139 | |
057bc350 | 140 | fan[1-*]_input Fan input value. |
1da177e4 | 141 | Unit: revolution/min (RPM) |
057bc350 | 142 | RO |
1da177e4 | 143 | |
057bc350 | 144 | fan[1-*]_div Fan divisor. |
1da177e4 | 145 | Integer value in powers of two (1, 2, 4, 8, 16, 32, 64, 128). |
057bc350 | 146 | RW |
1da177e4 LT |
147 | Some chips only support values 1, 2, 4 and 8. |
148 | Note that this is actually an internal clock divisor, which | |
149 | affects the measurable speed range, not the read value. | |
150 | ||
057bc350 RM |
151 | Also see the Alarms section for status flags associated with fans. |
152 | ||
153 | ||
1da177e4 LT |
154 | ******* |
155 | * PWM * | |
156 | ******* | |
157 | ||
057bc350 | 158 | pwm[1-*] Pulse width modulation fan control. |
1da177e4 | 159 | Integer value in the range 0 to 255 |
057bc350 | 160 | RW |
1da177e4 LT |
161 | 255 is max or 100%. |
162 | ||
057bc350 | 163 | pwm[1-*]_enable |
1da177e4 LT |
164 | Switch PWM on and off. |
165 | Not always present even if fan*_pwm is. | |
057bc350 RM |
166 | 0: turn off |
167 | 1: turn on in manual mode | |
168 | 2+: turn on in automatic mode | |
169 | Check individual chip documentation files for automatic mode details. | |
170 | RW | |
171 | ||
172 | pwm[1-*]_mode | |
173 | 0: DC mode | |
174 | 1: PWM mode | |
175 | RW | |
1da177e4 LT |
176 | |
177 | pwm[1-*]_auto_channels_temp | |
178 | Select which temperature channels affect this PWM output in | |
179 | auto mode. Bitfield, 1 is temp1, 2 is temp2, 4 is temp3 etc... | |
180 | Which values are possible depend on the chip used. | |
057bc350 | 181 | RW |
1da177e4 LT |
182 | |
183 | pwm[1-*]_auto_point[1-*]_pwm | |
184 | pwm[1-*]_auto_point[1-*]_temp | |
185 | pwm[1-*]_auto_point[1-*]_temp_hyst | |
186 | Define the PWM vs temperature curve. Number of trip points is | |
187 | chip-dependent. Use this for chips which associate trip points | |
188 | to PWM output channels. | |
057bc350 | 189 | RW |
1da177e4 LT |
190 | |
191 | OR | |
192 | ||
193 | temp[1-*]_auto_point[1-*]_pwm | |
194 | temp[1-*]_auto_point[1-*]_temp | |
195 | temp[1-*]_auto_point[1-*]_temp_hyst | |
196 | Define the PWM vs temperature curve. Number of trip points is | |
197 | chip-dependent. Use this for chips which associate trip points | |
198 | to temperature channels. | |
057bc350 | 199 | RW |
1da177e4 LT |
200 | |
201 | ||
202 | **************** | |
203 | * Temperatures * | |
204 | **************** | |
205 | ||
057bc350 | 206 | temp[1-*]_type Sensor type selection. |
e53004e2 | 207 | Integers 1 to 4 or thermistor Beta value (typically 3435) |
057bc350 | 208 | RW |
1da177e4 LT |
209 | 1: PII/Celeron Diode |
210 | 2: 3904 transistor | |
211 | 3: thermal diode | |
e53004e2 | 212 | 4: thermistor (default/unknown Beta) |
1da177e4 LT |
213 | Not all types are supported by all chips |
214 | ||
057bc350 | 215 | temp[1-*]_max Temperature max value. |
1da177e4 | 216 | Unit: millidegree Celcius |
057bc350 | 217 | RW |
1da177e4 | 218 | |
057bc350 | 219 | temp[1-*]_min Temperature min value. |
1da177e4 | 220 | Unit: millidegree Celcius |
057bc350 | 221 | RW |
1da177e4 | 222 | |
057bc350 | 223 | temp[1-*]_max_hyst |
1da177e4 LT |
224 | Temperature hysteresis value for max limit. |
225 | Unit: millidegree Celcius | |
226 | Must be reported as an absolute temperature, NOT a delta | |
227 | from the max value. | |
057bc350 | 228 | RW |
1da177e4 | 229 | |
057bc350 | 230 | temp[1-*]_input Temperature input value. |
1da177e4 | 231 | Unit: millidegree Celcius |
057bc350 | 232 | RO |
1da177e4 | 233 | |
057bc350 | 234 | temp[1-*]_crit Temperature critical value, typically greater than |
1da177e4 LT |
235 | corresponding temp_max values. |
236 | Unit: millidegree Celcius | |
057bc350 | 237 | RW |
1da177e4 | 238 | |
057bc350 | 239 | temp[1-*]_crit_hyst |
1da177e4 LT |
240 | Temperature hysteresis value for critical limit. |
241 | Unit: millidegree Celcius | |
242 | Must be reported as an absolute temperature, NOT a delta | |
243 | from the critical value. | |
057bc350 | 244 | RW |
1da177e4 | 245 | |
59ac8367 HR |
246 | temp[1-4]_offset |
247 | Temperature offset which is added to the temperature reading | |
248 | by the chip. | |
249 | Unit: millidegree Celsius | |
250 | Read/Write value. | |
251 | ||
1da177e4 LT |
252 | If there are multiple temperature sensors, temp1_* is |
253 | generally the sensor inside the chip itself, | |
254 | reported as "motherboard temperature". temp2_* to | |
255 | temp4_* are generally sensors external to the chip | |
256 | itself, for example the thermal diode inside the CPU or | |
257 | a thermistor nearby. | |
258 | ||
057bc350 RM |
259 | Also see the Alarms section for status flags associated with temperatures. |
260 | ||
1da177e4 LT |
261 | |
262 | ************ | |
263 | * Currents * | |
264 | ************ | |
265 | ||
266 | Note that no known chip provides current measurements as of writing, | |
267 | so this part is theoretical, so to say. | |
268 | ||
057bc350 | 269 | curr[1-*]_max Current max value |
1da177e4 | 270 | Unit: milliampere |
057bc350 | 271 | RW |
1da177e4 | 272 | |
057bc350 | 273 | curr[1-*]_min Current min value. |
1da177e4 | 274 | Unit: milliampere |
057bc350 | 275 | RW |
1da177e4 | 276 | |
057bc350 | 277 | curr[1-*]_input Current input value |
1da177e4 | 278 | Unit: milliampere |
057bc350 | 279 | RO |
1da177e4 LT |
280 | |
281 | ||
400b48ec JD |
282 | ********** |
283 | * Alarms * | |
284 | ********** | |
285 | ||
286 | Each channel or limit may have an associated alarm file, containing a | |
287 | boolean value. 1 means than an alarm condition exists, 0 means no alarm. | |
288 | ||
289 | Usually a given chip will either use channel-related alarms, or | |
290 | limit-related alarms, not both. The driver should just reflect the hardware | |
291 | implementation. | |
292 | ||
057bc350 RM |
293 | in[0-*]_alarm |
294 | fan[1-*]_alarm | |
295 | temp[1-*]_alarm | |
400b48ec | 296 | Channel alarm |
057bc350 RM |
297 | 0: no alarm |
298 | 1: alarm | |
299 | RO | |
400b48ec JD |
300 | |
301 | OR | |
302 | ||
057bc350 RM |
303 | in[0-*]_min_alarm |
304 | in[0-*]_max_alarm | |
305 | fan[1-*]_min_alarm | |
306 | temp[1-*]_min_alarm | |
307 | temp[1-*]_max_alarm | |
308 | temp[1-*]_crit_alarm | |
400b48ec | 309 | Limit alarm |
057bc350 RM |
310 | 0: no alarm |
311 | 1: alarm | |
312 | RO | |
400b48ec JD |
313 | |
314 | Each input channel may have an associated fault file. This can be used | |
315 | to notify open diodes, unconnected fans etc. where the hardware | |
316 | supports it. When this boolean has value 1, the measurement for that | |
317 | channel should not be trusted. | |
318 | ||
057bc350 RM |
319 | in[0-*]_input_fault |
320 | fan[1-*]_input_fault | |
321 | temp[1-*]_input_fault | |
400b48ec | 322 | Input fault condition |
057bc350 RM |
323 | 0: no fault occured |
324 | 1: fault condition | |
325 | RO | |
400b48ec JD |
326 | |
327 | Some chips also offer the possibility to get beeped when an alarm occurs: | |
328 | ||
329 | beep_enable Master beep enable | |
057bc350 RM |
330 | 0: no beeps |
331 | 1: beeps | |
332 | RW | |
400b48ec | 333 | |
057bc350 RM |
334 | in[0-*]_beep |
335 | fan[1-*]_beep | |
336 | temp[1-*]_beep | |
400b48ec | 337 | Channel beep |
057bc350 RM |
338 | 0: disable |
339 | 1: enable | |
340 | RW | |
400b48ec JD |
341 | |
342 | In theory, a chip could provide per-limit beep masking, but no such chip | |
343 | was seen so far. | |
344 | ||
345 | Old drivers provided a different, non-standard interface to alarms and | |
346 | beeps. These interface files are deprecated, but will be kept around | |
347 | for compatibility reasons: | |
1da177e4 LT |
348 | |
349 | alarms Alarm bitmask. | |
057bc350 | 350 | RO |
1da177e4 LT |
351 | Integer representation of one to four bytes. |
352 | A '1' bit means an alarm. | |
353 | Chips should be programmed for 'comparator' mode so that | |
354 | the alarm will 'come back' after you read the register | |
355 | if it is still valid. | |
356 | Generally a direct representation of a chip's internal | |
357 | alarm registers; there is no standard for the position | |
400b48ec JD |
358 | of individual bits. For this reason, the use of this |
359 | interface file for new drivers is discouraged. Use | |
360 | individual *_alarm and *_fault files instead. | |
1da177e4 LT |
361 | Bits are defined in kernel/include/sensors.h. |
362 | ||
1da177e4 | 363 | beep_mask Bitmask for beep. |
400b48ec JD |
364 | Same format as 'alarms' with the same bit locations, |
365 | use discouraged for the same reason. Use individual | |
366 | *_beep files instead. | |
057bc350 | 367 | RW |
1da177e4 | 368 | |
400b48ec JD |
369 | |
370 | ********* | |
371 | * Other * | |
372 | ********* | |
373 | ||
1da177e4 | 374 | eeprom Raw EEPROM data in binary form. |
057bc350 | 375 | RO |
c3df5806 JD |
376 | |
377 | pec Enable or disable PEC (SMBus only) | |
057bc350 RM |
378 | 0: disable |
379 | 1: enable | |
380 | RW |