Naming and data format standards for sysfs files ------------------------------------------------ The libsensors library offers an interface to the raw sensors data through the sysfs interface. See libsensors documentation and source for more further information. As of writing this document, libsensors (from lm_sensors 2.8.3) is heavily chip-dependant. Adding or updating support for any given chip requires modifying the library's code. This is because libsensors was written for the procfs interface older kernel modules were using, which wasn't standardized enough. Recent versions of libsensors (from lm_sensors 2.8.2 and later) have support for the sysfs interface, though. The new sysfs interface was designed to be as chip-independant as possible. Note that motherboards vary widely in the connections to sensor chips. There is no standard that ensures, for example, that the second temperature sensor is connected to the CPU, or that the second fan is on the CPU. Also, some values reported by the chips need some computation before they make full sense. For example, most chips can only measure voltages between 0 and +4V. Other voltages are scaled back into that range using external resistors. Since the values of these resistors can change from motherboard to motherboard, the conversions cannot be hard coded into the driver and have to be done in user space. For this reason, even if we aim at a chip-independant libsensors, it will still require a configuration file (e.g. /etc/sensors.conf) for proper values conversion, labeling of inputs and hiding of unused inputs. An alternative method that some programs use is to access the sysfs files directly. This document briefly describes the standards that the drivers follow, so that an application program can scan for entries and access this data in a simple and consistent way. That said, such programs will have to implement conversion, labeling and hiding of inputs. For this reason, it is still not recommended to bypass the library. If you are developing a userspace application please send us feedback on this standard. Note that this standard isn't completely established yet, so it is subject to changes, even important ones. One more reason to use the library instead of accessing sysfs files directly. Each chip gets its own directory in the sysfs /sys/devices tree. To find all sensor chips, it is easier to follow the symlinks from /sys/i2c/devices/ All sysfs values are fixed point numbers. To get the true value of some of the values, you should divide by the specified value. There is only one value per file, unlike the older /proc specification. The common scheme for files naming is: _. Usual types for sensor chips are "in" (voltage), "temp" (temperature) and "fan" (fan). Usual items are "input" (measured value), "max" (high threshold, "min" (low threshold). Numbering usually starts from 1, except for voltages which start from 0 (because most data sheets use this). A number is always used for elements that can be present more than once, even if there is a single element of the given type on the specific chip. Other files do not refer to a specific element, so they have a simple name, and no number. Alarms are direct indications read from the chips. The drivers do NOT make comparisons of readings to thresholds. This allows violations between readings to be caught and alarmed. The exact definition of an alarm (for example, whether a threshold must be met or must be exceeded to cause an alarm) is chip-dependent. ------------------------------------------------------------------------- ************ * Voltages * ************ in[0-8]_min Voltage min value. Unit: millivolt Read/Write in[0-8]_max Voltage max value. Unit: millivolt Read/Write in[0-8]_input Voltage input value. Unit: millivolt Read only Actual voltage depends on the scaling resistors on the motherboard, as recommended in the chip datasheet. This varies by chip and by motherboard. Because of this variation, values are generally NOT scaled by the chip driver, and must be done by the application. However, some drivers (notably lm87 and via686a) do scale, with various degrees of success. These drivers will output the actual voltage. Typical usage: in0_* CPU #1 voltage (not scaled) in1_* CPU #2 voltage (not scaled) in2_* 3.3V nominal (not scaled) in3_* 5.0V nominal (scaled) in4_* 12.0V nominal (scaled) in5_* -12.0V nominal (scaled) in6_* -5.0V nominal (scaled) in7_* varies in8_* varies cpu[0-1]_vid CPU core reference voltage. Unit: millivolt Read only. Not always correct. vrm Voltage Regulator Module version number. Read only. Two digit number, first is major version, second is minor version. Affects the way the driver calculates the CPU core reference voltage from the vid pins. ******** * Fans * ******** fan[1-3]_min Fan minimum value Unit: revolution/min (RPM) Read/Write. fan[1-3]_input Fan input value. Unit: revolution/min (RPM) Read only. fan[1-3]_div Fan divisor. Integer value in powers of two (1, 2, 4, 8, 16, 32, 64, 128). Some chips only support values 1, 2, 4 and 8. Note that this is actually an internal clock divisor, which affects the measurable speed range, not the read value. ******* * PWM * ******* pwm[1-3] Pulse width modulation fan control. Integer value in the range 0 to 255 Read/Write 255 is max or 100%. pwm[1-3]_enable Switch PWM on and off. Not always present even if fan*_pwm is. 0 to turn off 1 to turn on in manual mode 2 to turn on in automatic mode Read/Write pwm[1-*]_auto_channels_temp Select which temperature channels affect this PWM output in auto mode. Bitfield, 1 is temp1, 2 is temp2, 4 is temp3 etc... Which values are possible depend on the chip used. pwm[1-*]_auto_point[1-*]_pwm pwm[1-*]_auto_point[1-*]_temp pwm[1-*]_auto_point[1-*]_temp_hyst Define the PWM vs temperature curve. Number of trip points is chip-dependent. Use this for chips which associate trip points to PWM output channels. OR temp[1-*]_auto_point[1-*]_pwm temp[1-*]_auto_point[1-*]_temp temp[1-*]_auto_point[1-*]_temp_hyst Define the PWM vs temperature curve. Number of trip points is chip-dependent. Use this for chips which associate trip points to temperature channels. **************** * Temperatures * **************** temp[1-3]_type Sensor type selection. Integers 1, 2, 3 or thermistor Beta value (3435) Read/Write. 1: PII/Celeron Diode 2: 3904 transistor 3: thermal diode Not all types are supported by all chips temp[1-4]_max Temperature max value. Unit: millidegree Celcius Read/Write value. temp[1-3]_min Temperature min value. Unit: millidegree Celcius Read/Write value. temp[1-3]_max_hyst Temperature hysteresis value for max limit. Unit: millidegree Celcius Must be reported as an absolute temperature, NOT a delta from the max value. Read/Write value. temp[1-4]_input Temperature input value. Unit: millidegree Celcius Read only value. temp[1-4]_crit Temperature critical value, typically greater than corresponding temp_max values. Unit: millidegree Celcius Read/Write value. temp[1-2]_crit_hyst Temperature hysteresis value for critical limit. Unit: millidegree Celcius Must be reported as an absolute temperature, NOT a delta from the critical value. Read/Write value. If there are multiple temperature sensors, temp1_* is generally the sensor inside the chip itself, reported as "motherboard temperature". temp2_* to temp4_* are generally sensors external to the chip itself, for example the thermal diode inside the CPU or a thermistor nearby. ************ * Currents * ************ Note that no known chip provides current measurements as of writing, so this part is theoretical, so to say. curr[1-n]_max Current max value Unit: milliampere Read/Write. curr[1-n]_min Current min value. Unit: milliampere Read/Write. curr[1-n]_input Current input value Unit: milliampere Read only. ********* * Other * ********* alarms Alarm bitmask. Read only. Integer representation of one to four bytes. A '1' bit means an alarm. Chips should be programmed for 'comparator' mode so that the alarm will 'come back' after you read the register if it is still valid. Generally a direct representation of a chip's internal alarm registers; there is no standard for the position of individual bits. Bits are defined in kernel/include/sensors.h. beep_enable Beep/interrupt enable 0 to disable. 1 to enable. Read/Write beep_mask Bitmask for beep. Same format as 'alarms' with the same bit locations. Read/Write eeprom Raw EEPROM data in binary form. Read only.