1 Naming and data format standards for sysfs files
2 ------------------------------------------------
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.
14 The new sysfs interface was designed to be as chip-independant as
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.
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.
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.
38 If you are developing a userspace application please send us feedback on
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.
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
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.
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.
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.
70 -------------------------------------------------------------------------
72 [0-*] denotes any positive number starting from 0
73 [1-*] denotes any positive number starting from 1
77 Read/write values may be read-only for some chips, depending on the
78 hardware implementation.
84 in[0-*]_min Voltage min value.
88 in[0-*]_max Voltage max value.
92 in[0-*]_input Voltage input value.
95 Voltage measured on the chip pin.
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)
102 do scale, because of internal resistors built into a chip.
103 These drivers will output the actual voltage.
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)
116 cpu[0-*]_vid CPU core reference voltage.
121 vrm Voltage Regulator Module version number.
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
126 Affects the way the driver calculates the CPU core reference
127 voltage from the vid pins.
129 Also see the Alarms section for status flags associated with voltages.
136 fan[1-*]_min Fan minimum value
137 Unit: revolution/min (RPM)
140 fan[1-*]_input Fan input value.
141 Unit: revolution/min (RPM)
144 fan[1-*]_div Fan divisor.
145 Integer value in powers of two (1, 2, 4, 8, 16, 32, 64, 128).
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.
151 Also see the Alarms section for status flags associated with fans.
158 pwm[1-*] Pulse width modulation fan control.
159 Integer value in the range 0 to 255
164 Switch PWM on and off.
165 Not always present even if fan*_pwm is.
167 1: turn on in manual mode
168 2+: turn on in automatic mode
169 Check individual chip documentation files for automatic mode details.
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.
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.
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.
206 temp[1-*]_type Sensor type selection.
207 Integers 1 to 4 or thermistor Beta value (typically 3435)
212 4: thermistor (default/unknown Beta)
213 Not all types are supported by all chips
215 temp[1-*]_max Temperature max value.
216 Unit: millidegree Celcius
219 temp[1-*]_min Temperature min value.
220 Unit: millidegree Celcius
224 Temperature hysteresis value for max limit.
225 Unit: millidegree Celcius
226 Must be reported as an absolute temperature, NOT a delta
230 temp[1-*]_input Temperature input value.
231 Unit: millidegree Celcius
234 temp[1-*]_crit Temperature critical value, typically greater than
235 corresponding temp_max values.
236 Unit: millidegree Celcius
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.
247 Temperature offset which is added to the temperature reading
249 Unit: millidegree Celsius
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
259 Also see the Alarms section for status flags associated with temperatures.
266 Note that no known chip provides current measurements as of writing,
267 so this part is theoretical, so to say.
269 curr[1-*]_max Current max value
273 curr[1-*]_min Current min value.
277 curr[1-*]_input Current input value
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.
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
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.
321 temp[1-*]_input_fault
322 Input fault condition
327 Some chips also offer the possibility to get beeped when an alarm occurs:
329 beep_enable Master beep enable
342 In theory, a chip could provide per-limit beep masking, but no such chip
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:
349 alarms Alarm bitmask.
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
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.
361 Bits are defined in kernel/include/sensors.h.
363 beep_mask Bitmask for beep.
364 Same format as 'alarms' with the same bit locations,
365 use discouraged for the same reason. Use individual
366 *_beep files instead.
374 eeprom Raw EEPROM data in binary form.
377 pec Enable or disable PEC (SMBus only)
git://ftp.safe.ca / safe / jmp / linux-2.6 / blob