Naming and data format standards for sysfs files------------------------------------------------ The libsensors library offers an interface to the raw sensors datathrough the sysfs interface. Since lm-sensors 3.0.0, libsensors iscompletely chip-independent. It assumes that all the kernel driversimplement the standard sysfs interface described in this document.This makes adding or updating support for any given chip very easy, aslibsensors, and applications using it, do not need to be modified.This is a major improvement compared to lm-sensors 2. Note that motherboards vary widely in the connections to sensor chips.There is no standard that ensures, for example, that the secondtemperature sensor is connected to the CPU, or that the second fan is onthe CPU. Also, some values reported by the chips need some computationbefore they make full sense. For example, most chips can only measurevoltages between 0 and +4V. Other voltages are scaled back into thatrange using external resistors. Since the values of these resistorscan change from motherboard to motherboard, the conversions cannot behard coded into the driver and have to be done in user space. For this reason, even if we aim at a chip-independent libsensors, it willstill require a configuration file (e.g. /etc/sensors.conf) for propervalues conversion, labeling of inputs and hiding of unused inputs. An alternative method that some programs use is to access the sysfsfiles directly. This document briefly describes the standards that thedrivers follow, so that an application program can scan for entries andaccess this data in a simple and consistent way. That said, such programswill have to implement conversion, labeling and hiding of inputs. Forthis reason, it is still not recommended to bypass the library. Each chip gets its own directory in the sysfs /sys/devices tree.  Tofind all sensor chips, it is easier to follow the device symlinks from/sys/class/hwmon/hwmon*. Up to lm-sensors 3.0.0, libsensors looks for hardware monitoring attributesin the "physical" device directory. Since lm-sensors 3.0.1, attributes foundin the hwmon "class" device directory are also supported. Complex drivers(e.g. drivers for multifunction chips) may want to use this possibility toavoid namespace pollution. The only drawback will be that older versions oflibsensors won't support the driver in question. All sysfs values are fixed point numbers. There is only one value per file, unlike the older /proc specification.The common scheme for files naming is: <type><number>_<item>. Usualtypes for sensor chips are "in" (voltage), "temp" (temperature) and"fan" (fan). Usual items are "input" (measured value), "max" (highthreshold, "min" (low threshold). Numbering usually starts from 1,except for voltages which start from 0 (because most data sheets usethis). A number is always used for elements that can be present morethan once, even if there is a single element of the given type on thespecific chip. Other files do not refer to a specific element, sothey have a simple name, and no number. Alarms are direct indications read from the chips. The drivers do NOTmake comparisons of readings to thresholds. This allows violationsbetween readings to be caught and alarmed. The exact definition of analarm (for example, whether a threshold must be met or must be exceededto cause an alarm) is chip-dependent. When setting values of hwmon sysfs attributes, the string representation ofthe desired value must be written, note that strings which are not a numberare interpreted as 0! For more on how written strings are interpreted see the"sysfs attribute writes interpretation" section at the end of this file. ------------------------------------------------------------------------- [0-*]	denotes any positive number starting from 0[1-*]	denotes any positive number starting from 1RO	read only valueWO	write only valueRW	read/write value Read/write values may be read-only for some chips, depending on thehardware implementation. All entries (except name) are optional, and should only be created in agiven driver if the chip has the feature.  ********************** Global attributes ********************** name		The chip name.		This should be a short, lowercase string, not containing		spaces nor dashes, representing the chip name. This is		the only mandatory attribute.		I2C devices get this attribute created automatically.		RO update_interval	The interval at which the chip will update readings.		Unit: millisecond		RW		Some devices have a variable update rate or interval.		This attribute can be used to change it to the desired value.  ************* Voltages ************* in[0-*]_min	Voltage min value.		Unit: millivolt		RW		in[0-*]_lcrit	Voltage critical min value.		Unit: millivolt		RW		If voltage drops to or below this limit, the system may		take drastic action such as power down or reset. At the very		least, it should report a fault. in[0-*]_max	Voltage max value.		Unit: millivolt		RW		in[0-*]_crit	Voltage critical max value.		Unit: millivolt		RW		If voltage reaches or exceeds this limit, the system may		take drastic action such as power down or reset. At the very		least, it should report a fault. in[0-*]_input	Voltage input value.		Unit: millivolt		RO		Voltage measured on the chip pin.		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, because of internal resistors built into a chip.		These drivers will output the actual voltage. Rule of		thumb: drivers should report the voltage values at the		"pins" of the chip. in[0-*]_average		Average voltage		Unit: millivolt		RO in[0-*]_lowest		Historical minimum voltage		Unit: millivolt		RO in[0-*]_highest		Historical maximum voltage		Unit: millivolt		RO in[0-*]_reset_history		Reset inX_lowest and inX_highest		WO in_reset_history		Reset inX_lowest and inX_highest for all sensors		WO in[0-*]_label	Suggested voltage channel label.		Text string		Should only be created if the driver has hints about what		this voltage channel is being used for, and user-space		doesn't. In all other cases, the label is provided by		user-space.		RO cpu[0-*]_vid	CPU core reference voltage.		Unit: millivolt		RO		Not always correct. vrm		Voltage Regulator Module version number. 		RW (but changing it should no more be necessary)		Originally the VRM standard version multiplied by 10, but now		an arbitrary number, as not all standards have a version		number.		Affects the way the driver calculates the CPU core reference		voltage from the vid pins. Also see the Alarms section for status flags associated with voltages.  ********* Fans ********* fan[1-*]_min	Fan minimum value		Unit: revolution/min (RPM)		RW fan[1-*]_max	Fan maximum value		Unit: revolution/min (RPM)		Only rarely supported by the hardware.		RW fan[1-*]_input	Fan input value.		Unit: revolution/min (RPM)		RO fan[1-*]_div	Fan divisor.		Integer value in powers of two (1, 2, 4, 8, 16, 32, 64, 128).		RW		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. fan[1-*]_pulses	Number of tachometer pulses per fan revolution.		Integer value, typically between 1 and 4.		RW		This value is a characteristic of the fan connected to the		device's input, so it has to be set in accordance with the fan		model.		Should only be created if the chip has a register to configure		the number of pulses. In the absence of such a register (and		thus attribute) the value assumed by all devices is 2 pulses		per fan revolution. fan[1-*]_target		Desired fan speed		Unit: revolution/min (RPM)		RW		Only makes sense if the chip supports closed-loop fan speed		control based on the measured fan speed. fan[1-*]_label	Suggested fan channel label.		Text string		Should only be created if the driver has hints about what		this fan channel is being used for, and user-space doesn't.		In all other cases, the label is provided by user-space.		RO Also see the Alarms section for status flags associated with fans.  ******** PWM ******** pwm[1-*]	Pulse width modulation fan control.		Integer value in the range 0 to 255		RW		255 is max or 100%. pwm[1-*]_enable		Fan speed control method:		0: no fan speed control (i.e. fan at full speed)		1: manual fan speed control enabled (using pwm[1-*])		2+: automatic fan speed control enabled		Check individual chip documentation files for automatic mode		details.		RW pwm[1-*]_mode	0: DC mode (direct current)		1: PWM mode (pulse-width modulation)		RW pwm[1-*]_freq	Base PWM frequency in Hz.		Only possibly available when pwmN_mode is PWM, but not always		present even then.		RW 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.		RW pwm[1-*]_auto_point[1-*]_pwmpwm[1-*]_auto_point[1-*]_temppwm[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.		RW temp[1-*]_auto_point[1-*]_pwmtemp[1-*]_auto_point[1-*]_temptemp[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.		RW There is a third case where trip points are associated to both PWM outputchannels and temperature channels: the PWM values are associated to PWMoutput channels while the temperature values are associated to temperaturechannels. In that case, the result is determined by the mapping betweentemperature inputs and PWM outputs. When several temperature inputs aremapped to a given PWM output, this leads to several candidate PWM values.The actual result is up to the chip, but in general the highest candidatevalue (fastest fan speed) wins.  ***************** Temperatures ***************** temp[1-*]_type	Sensor type selection.		Integers 1 to 6		RW		1: CPU embedded diode		2: 3904 transistor		3: thermal diode		4: thermistor		5: AMD AMDSI		6: Intel PECI		Not all types are supported by all chips temp[1-*]_max	Temperature max value.		Unit: millidegree Celsius (or millivolt, see below)		RW temp[1-*]_min	Temperature min value.		Unit: millidegree Celsius		RW temp[1-*]_max_hyst		Temperature hysteresis value for max limit.		Unit: millidegree Celsius		Must be reported as an absolute temperature, NOT a delta		from the max value.		RW temp[1-*]_input Temperature input value.		Unit: millidegree Celsius		RO temp[1-*]_crit	Temperature critical max value, typically greater than		corresponding temp_max values.		Unit: millidegree Celsius		RW temp[1-*]_crit_hyst		Temperature hysteresis value for critical limit.		Unit: millidegree Celsius		Must be reported as an absolute temperature, NOT a delta		from the critical value.		RW temp[1-*]_emergency		Temperature emergency max value, for chips supporting more than		two upper temperature limits. Must be equal or greater than		corresponding temp_crit values.		Unit: millidegree Celsius		RW temp[1-*]_emergency_hyst		Temperature hysteresis value for emergency limit.		Unit: millidegree Celsius		Must be reported as an absolute temperature, NOT a delta		from the emergency value.		RW temp[1-*]_lcrit	Temperature critical min value, typically lower than		corresponding temp_min values.		Unit: millidegree Celsius		RW temp[1-*]_offset		Temperature offset which is added to the temperature reading		by the chip.		Unit: millidegree Celsius		Read/Write value. temp[1-*]_label	Suggested temperature channel label.		Text string		Should only be created if the driver has hints about what		this temperature channel is being used for, and user-space		doesn't. In all other cases, the label is provided by		user-space.		RO temp[1-*]_lowest		Historical minimum temperature		Unit: millidegree Celsius		RO temp[1-*]_highest		Historical maximum temperature		Unit: millidegree Celsius		RO temp[1-*]_reset_history		Reset temp_lowest and temp_highest		WO temp_reset_history		Reset temp_lowest and temp_highest for all sensors		WO Some chips measure temperature using external thermistors and an ADC, andreport the temperature measurement as a voltage. Converting this voltageback to a temperature (or the other way around for limits) requiresmathematical functions not available in the kernel, so the conversionmust occur in user space. For these chips, all temp* files describedabove should contain values expressed in millivolt instead of millidegreeCelsius. In other words, such temperature channels are handled as voltagechannels by the driver. Also see the Alarms section for status flags associated with temperatures.  ************* Currents ************* curr[1-*]_max	Current max value		Unit: milliampere		RW curr[1-*]_min	Current min value.		Unit: milliampere		RW curr[1-*]_lcrit	Current critical low value		Unit: milliampere		RW curr[1-*]_crit	Current critical high value.		Unit: milliampere		RW curr[1-*]_input	Current input value		Unit: milliampere		RO curr[1-*]_average		Average current use		Unit: milliampere		RO curr[1-*]_lowest		Historical minimum current		Unit: milliampere		RO curr[1-*]_highest		Historical maximum current		Unit: milliampere		RO curr[1-*]_reset_history		Reset currX_lowest and currX_highest		WO curr_reset_history		Reset currX_lowest and currX_highest for all sensors		WO Also see the Alarms section for status flags associated with currents. ********** Power ********** power[1-*]_average		Average power use				Unit: microWatt				RO power[1-*]_average_interval	Power use averaging interval.  A poll				notification is sent to this file if the				hardware changes the averaging interval.				Unit: milliseconds				RW power[1-*]_average_interval_max	Maximum power use averaging interval				Unit: milliseconds				RO power[1-*]_average_interval_min	Minimum power use averaging interval				Unit: milliseconds				RO power[1-*]_average_highest	Historical average maximum power use				Unit: microWatt				RO power[1-*]_average_lowest	Historical average minimum power use				Unit: microWatt				RO power[1-*]_average_max		A poll notification is sent to				power[1-*]_average when power use				rises above this value.				Unit: microWatt				RW power[1-*]_average_min		A poll notification is sent to				power[1-*]_average when power use				sinks below this value.				Unit: microWatt				RW power[1-*]_input		Instantaneous power use

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