------------------------------------------------
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.
+through the sysfs interface. Since lm-sensors 3.0.0, libsensors is
+completely chip-independent. It assumes that all the kernel drivers
+implement the standard sysfs interface described in this document.
+This makes adding or updating support for any given chip very easy, as
+libsensors, 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 second
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
+For this reason, even if we aim at a chip-independent 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.
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/
+find all sensor chips, it is easier to follow the device symlinks from
+/sys/class/hwmon/hwmon*.
-All sysfs values are fixed point numbers. To get the true value of some
-of the values, you should divide by the specified value.
+Up to lm-sensors 3.0.0, libsensors looks for hardware monitoring attributes
+in the "physical" device directory. Since lm-sensors 3.0.1, attributes found
+in the hwmon "class" device directory are also supported. Complex drivers
+(e.g. drivers for multifunction chips) may want to use this possibility to
+avoid namespace pollution. The only drawback will be that older versions of
+libsensors 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>. Usual
alarm (for example, whether a threshold must be met or must be exceeded
to cause an alarm) is chip-dependent.
+When setting values of hwmon sysfs attributes, the string representation of
+the desired value must be written, note that strings which are not a number
+are 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 1
RO read only value
+WO write only value
RW read/write value
Read/write values may be read-only for some chips, depending on the
hardware implementation.
+All entries (except name) are optional, and should only be created in a
+given 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_rate The rate at which the chip will update readings.
+ Unit: millisecond
+ RW
+ Some devices have a variable update rate. This attribute
+ can be used to change the update rate to the desired
+ frequency.
+
+
************
* Voltages *
************
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.
-
- 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
+ These drivers will output the actual voltage. Rule of
+ thumb: drivers should report the voltage values at the
+ "pins" of the chip.
+
+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
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
Note that this is actually an internal clock divisor, which
affects the measurable speed range, not the read value.
+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.
255 is max or 100%.
pwm[1-*]_enable
- Switch PWM on and off.
- Not always present even if fan*_pwm is.
- 0: turn off
- 1: turn on in manual mode
- 2+: turn on in automatic mode
- Check individual chip documentation files for automatic mode details.
+ 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-*]_mode
- 0: DC mode
- 1: PWM mode
+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
to PWM output channels.
RW
-OR
-
temp[1-*]_auto_point[1-*]_pwm
temp[1-*]_auto_point[1-*]_temp
temp[1-*]_auto_point[1-*]_temp_hyst
to temperature channels.
RW
+There is a third case where trip points are associated to both PWM output
+channels and temperature channels: the PWM values are associated to PWM
+output channels while the temperature values are associated to temperature
+channels. In that case, the result is determined by the mapping between
+temperature inputs and PWM outputs. When several temperature inputs are
+mapped 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 candidate
+value (fastest fan speed) wins.
+
****************
* Temperatures *
****************
temp[1-*]_type Sensor type selection.
- Integers 1 to 4 or thermistor Beta value (typically 3435)
+ Integers 1 to 6
RW
1: PII/Celeron Diode
2: 3904 transistor
3: thermal diode
- 4: thermistor (default/unknown Beta)
+ 4: thermistor
+ 5: AMD AMDSI
+ 6: Intel PECI
Not all types are supported by all chips
temp[1-*]_max Temperature max value.
- Unit: millidegree Celcius
+ Unit: millidegree Celsius (or millivolt, see below)
RW
temp[1-*]_min Temperature min value.
- Unit: millidegree Celcius
+ Unit: millidegree Celsius
RW
temp[1-*]_max_hyst
Temperature hysteresis value for max limit.
- Unit: millidegree Celcius
+ 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 Celcius
+ Unit: millidegree Celsius
RO
temp[1-*]_crit Temperature critical value, typically greater than
corresponding temp_max values.
- Unit: millidegree Celcius
+ Unit: millidegree Celsius
RW
temp[1-*]_crit_hyst
Temperature hysteresis value for critical limit.
- Unit: millidegree Celcius
+ Unit: millidegree Celsius
Must be reported as an absolute temperature, NOT a delta
from the critical value.
RW
-temp[1-4]_offset
+temp[1-*]_offset
Temperature offset which is added to the temperature reading
by the chip.
Unit: millidegree Celsius
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.
+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, and
+report the temperature measurement as a voltage. Converting this voltage
+back to a temperature (or the other way around for limits) requires
+mathematical functions not available in the kernel, so the conversion
+must occur in user space. For these chips, all temp* files described
+above should contain values expressed in millivolt instead of millidegree
+Celsius. In other words, such temperature channels are handled as voltage
+channels by the driver.
Also see the Alarms section for status flags associated with temperatures.
Unit: milliampere
RO
+*********
+* 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
+ Unit: microWatt
+ RO
+
+power[1-*]_input_highest Historical maximum power use
+ Unit: microWatt
+ RO
+
+power[1-*]_input_lowest Historical minimum power use
+ Unit: microWatt
+ RO
+
+power[1-*]_reset_history Reset input_highest, input_lowest,
+ average_highest and average_lowest.
+ WO
+
+power[1-*]_accuracy Accuracy of the power meter.
+ Unit: Percent
+ RO
+
+power[1-*]_alarm 1 if the system is drawing more power than the
+ cap allows; 0 otherwise. A poll notification is
+ sent to this file when the power use exceeds the
+ cap. This file only appears if the cap is known
+ to be enforced by hardware.
+ RO
+
+power[1-*]_cap If power use rises above this limit, the
+ system should take action to reduce power use.
+ A poll notification is sent to this file if the
+ cap is changed by the hardware. The *_cap
+ files only appear if the cap is known to be
+ enforced by hardware.
+ Unit: microWatt
+ RW
+
+power[1-*]_cap_hyst Margin of hysteresis built around capping and
+ notification.
+ Unit: microWatt
+ RW
+
+power[1-*]_cap_max Maximum cap that can be set.
+ Unit: microWatt
+ RO
+
+power[1-*]_cap_min Minimum cap that can be set.
+ Unit: microWatt
+ RO
+
+**********
+* Energy *
+**********
+
+energy[1-*]_input Cumulative energy use
+ Unit: microJoule
+ RO
+
**********
* Alarms *
in[0-*]_min_alarm
in[0-*]_max_alarm
fan[1-*]_min_alarm
+fan[1-*]_max_alarm
temp[1-*]_min_alarm
temp[1-*]_max_alarm
temp[1-*]_crit_alarm
supports it. When this boolean has value 1, the measurement for that
channel should not be trusted.
-in[0-*]_input_fault
-fan[1-*]_input_fault
-temp[1-*]_input_fault
+in[0-*]_fault
+fan[1-*]_fault
+temp[1-*]_fault
Input fault condition
0: no fault occured
1: fault condition
RW
-*********
-* Other *
-*********
+***********************
+* Intrusion detection *
+***********************
-eeprom Raw EEPROM data in binary form.
- RO
+intrusion[0-*]_alarm
+ Chassis intrusion detection
+ 0: OK
+ 1: intrusion detected
+ RW
+ Contrary to regular alarm flags which clear themselves
+ automatically when read, this one sticks until cleared by
+ the user. This is done by writing 0 to the file. Writing
+ other values is unsupported.
-pec Enable or disable PEC (SMBus only)
+intrusion[0-*]_beep
+ Chassis intrusion beep
0: disable
1: enable
RW
+
+
+sysfs attribute writes interpretation
+-------------------------------------
+
+hwmon sysfs attributes always contain numbers, so the first thing to do is to
+convert the input to a number, there are 2 ways todo this depending whether
+the number can be negative or not:
+unsigned long u = simple_strtoul(buf, NULL, 10);
+long s = simple_strtol(buf, NULL, 10);
+
+With buf being the buffer with the user input being passed by the kernel.
+Notice that we do not use the second argument of strto[u]l, and thus cannot
+tell when 0 is returned, if this was really 0 or is caused by invalid input.
+This is done deliberately as checking this everywhere would add a lot of
+code to the kernel.
+
+Notice that it is important to always store the converted value in an
+unsigned long or long, so that no wrap around can happen before any further
+checking.
+
+After the input string is converted to an (unsigned) long, the value should be
+checked if its acceptable. Be careful with further conversions on the value
+before checking it for validity, as these conversions could still cause a wrap
+around before the check. For example do not multiply the result, and only
+add/subtract if it has been divided before the add/subtract.
+
+What to do if a value is found to be invalid, depends on the type of the
+sysfs attribute that is being set. If it is a continuous setting like a
+tempX_max or inX_max attribute, then the value should be clamped to its
+limits using SENSORS_LIMIT(value, min_limit, max_limit). If it is not
+continuous like for example a tempX_type, then when an invalid value is
+written, -EINVAL should be returned.
+
+Example1, temp1_max, register is a signed 8 bit value (-128 - 127 degrees):
+
+ long v = simple_strtol(buf, NULL, 10) / 1000;
+ v = SENSORS_LIMIT(v, -128, 127);
+ /* write v to register */
+
+Example2, fan divider setting, valid values 2, 4 and 8:
+
+ unsigned long v = simple_strtoul(buf, NULL, 10);
+
+ switch (v) {
+ case 2: v = 1; break;
+ case 4: v = 2; break;
+ case 8: v = 3; break;
+ default:
+ return -EINVAL;
+ }
+ /* write v to register */
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