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
72 ************
73 * Voltages *
74 ************
75
76 in[0-8]_min Voltage min value.
77 Unit: millivolt
78 Read/Write
79
80 in[0-8]_max Voltage max value.
81 Unit: millivolt
82 Read/Write
83
84 in[0-8]_input Voltage input value.
85 Unit: millivolt
86 Read only
87 Actual voltage depends on the scaling resistors on the
88 motherboard, as recommended in the chip datasheet.
89 This varies by chip and by motherboard.
90 Because of this variation, values are generally NOT scaled
91 by the chip driver, and must be done by the application.
92 However, some drivers (notably lm87 and via686a)
93 do scale, with various degrees of success.
94 These drivers will output the actual voltage.
95
96 Typical usage:
97 in0_* CPU #1 voltage (not scaled)
98 in1_* CPU #2 voltage (not scaled)
99 in2_* 3.3V nominal (not scaled)
100 in3_* 5.0V nominal (scaled)
101 in4_* 12.0V nominal (scaled)
102 in5_* -12.0V nominal (scaled)
103 in6_* -5.0V nominal (scaled)
104 in7_* varies
105 in8_* varies
106
107 cpu[0-1]_vid CPU core reference voltage.
108 Unit: millivolt
109 Read only.
110 Not always correct.
111
112 vrm Voltage Regulator Module version number.
113 Read only.
114 Two digit number, first is major version, second is
115 minor version.
116 Affects the way the driver calculates the CPU core reference
117 voltage from the vid pins.
118
119
120 ********
121 * Fans *
122 ********
123
124 fan[1-3]_min Fan minimum value
125 Unit: revolution/min (RPM)
126 Read/Write.
127
128 fan[1-3]_input Fan input value.
129 Unit: revolution/min (RPM)
130 Read only.
131
132 fan[1-3]_div Fan divisor.
133 Integer value in powers of two (1, 2, 4, 8, 16, 32, 64, 128).
134 Some chips only support values 1, 2, 4 and 8.
135 Note that this is actually an internal clock divisor, which
136 affects the measurable speed range, not the read value.
137
138 *******
139 * PWM *
140 *******
141
142 pwm[1-3] Pulse width modulation fan control.
143 Integer value in the range 0 to 255
144 Read/Write
145 255 is max or 100%.
146
147 pwm[1-3]_enable
148 Switch PWM on and off.
149 Not always present even if fan*_pwm is.
150 0 to turn off
151 1 to turn on in manual mode
152 2 to turn on in automatic mode
153 Read/Write
154
155 pwm[1-*]_auto_channels_temp
156 Select which temperature channels affect this PWM output in
157 auto mode. Bitfield, 1 is temp1, 2 is temp2, 4 is temp3 etc...
158 Which values are possible depend on the chip used.
159
160 pwm[1-*]_auto_point[1-*]_pwm
161 pwm[1-*]_auto_point[1-*]_temp
162 pwm[1-*]_auto_point[1-*]_temp_hyst
163 Define the PWM vs temperature curve. Number of trip points is
164 chip-dependent. Use this for chips which associate trip points
165 to PWM output channels.
166
167 OR
168
169 temp[1-*]_auto_point[1-*]_pwm
170 temp[1-*]_auto_point[1-*]_temp
171 temp[1-*]_auto_point[1-*]_temp_hyst
172 Define the PWM vs temperature curve. Number of trip points is
173 chip-dependent. Use this for chips which associate trip points
174 to temperature channels.
175
176
177 ****************
178 * Temperatures *
179 ****************
180
181 temp[1-3]_type Sensor type selection.
182 Integers 1 to 4 or thermistor Beta value (typically 3435)
183 Read/Write.
184 1: PII/Celeron Diode
185 2: 3904 transistor
186 3: thermal diode
187 4: thermistor (default/unknown Beta)
188 Not all types are supported by all chips
189
190 temp[1-4]_max Temperature max value.
191 Unit: millidegree Celcius
192 Read/Write value.
193
194 temp[1-3]_min Temperature min value.
195 Unit: millidegree Celcius
196 Read/Write value.
197
198 temp[1-3]_max_hyst
199 Temperature hysteresis value for max limit.
200 Unit: millidegree Celcius
201 Must be reported as an absolute temperature, NOT a delta
202 from the max value.
203 Read/Write value.
204
205 temp[1-4]_input Temperature input value.
206 Unit: millidegree Celcius
207 Read only value.
208
209 temp[1-4]_crit Temperature critical value, typically greater than
210 corresponding temp_max values.
211 Unit: millidegree Celcius
212 Read/Write value.
213
214 temp[1-2]_crit_hyst
215 Temperature hysteresis value for critical limit.
216 Unit: millidegree Celcius
217 Must be reported as an absolute temperature, NOT a delta
218 from the critical value.
219 Read/Write value.
220
221 If there are multiple temperature sensors, temp1_* is
222 generally the sensor inside the chip itself,
223 reported as "motherboard temperature". temp2_* to
224 temp4_* are generally sensors external to the chip
225 itself, for example the thermal diode inside the CPU or
226 a thermistor nearby.
227
228
229 ************
230 * Currents *
231 ************
232
233 Note that no known chip provides current measurements as of writing,
234 so this part is theoretical, so to say.
235
236 curr[1-n]_max Current max value
237 Unit: milliampere
238 Read/Write.
239
240 curr[1-n]_min Current min value.
241 Unit: milliampere
242 Read/Write.
243
244 curr[1-n]_input Current input value
245 Unit: milliampere
246 Read only.
247
248
249 *********
250 * Other *
251 *********
252
253 alarms Alarm bitmask.
254 Read only.
255 Integer representation of one to four bytes.
256 A '1' bit means an alarm.
257 Chips should be programmed for 'comparator' mode so that
258 the alarm will 'come back' after you read the register
259 if it is still valid.
260 Generally a direct representation of a chip's internal
261 alarm registers; there is no standard for the position
262 of individual bits.
263 Bits are defined in kernel/include/sensors.h.
264
265 alarms_in Alarm bitmask relative to in (voltage) channels
266 Read only
267 A '1' bit means an alarm, LSB corresponds to in0 and so on
268 Prefered to 'alarms' for newer chips
269
270 alarms_fan Alarm bitmask relative to fan channels
271 Read only
272 A '1' bit means an alarm, LSB corresponds to fan1 and so on
273 Prefered to 'alarms' for newer chips
274
275 alarms_temp Alarm bitmask relative to temp (temperature) channels
276 Read only
277 A '1' bit means an alarm, LSB corresponds to temp1 and so on
278 Prefered to 'alarms' for newer chips
279
280 beep_enable Beep/interrupt enable
281 0 to disable.
282 1 to enable.
283 Read/Write
284
285 beep_mask Bitmask for beep.
286 Same format as 'alarms' with the same bit locations.
287 Read/Write
288
289 eeprom Raw EEPROM data in binary form.
290 Read only.
291
292 pec Enable or disable PEC (SMBus only)
293 Read/Write
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