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-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: <type><number>_<item>. 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.