path: root/lib/sensors.conf.5

.\" Copyright (C) 1998, 1999 Adrian Baugh <adrian.baugh@keble.ox.ac.uk> and
.\"                          Frodo Looijaard <frodol@dds.nl>
.\" Copyright (C) 2008--2012 Jean Delvare <jdelvare@suse.de>
.\"
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.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
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.\" References consulted:
.\"     sensors.conf.eg by Frodo Looijaard
.TH sensors.conf 5  "November 2012" "lm-sensors 3" "Linux User's Manual"
.SH NAME
sensors.conf \- libsensors configuration file

.SH DESCRIPTION
sensors.conf describes how libsensors, and so all programs using it, should
translate the raw readings from the kernel modules to real\-world values.

.SH SEMANTICS

On a given system, there may be one or more hardware monitoring chips.
Each chip may have several features. For example, the LM78 monitors 7
voltage inputs, 3 fans and one temperature. Feature names are
standardized. Typical feature names are in0, in1, in2... for voltage
inputs, fan1, fan2, fan3... for fans and temp1, temp2, temp3... for
temperature inputs.

Each feature may in turn have one or more sub\-features, each
representing an attribute of the feature: input value, low limit, high
limit, alarm, etc. Sub\-feature names are standardized as well. For
example, the first voltage input (in0) would typically have
sub\-features in0_input (measured value), in0_min (low limit), in0_max
(high limit) and in0_alarm (alarm flag). Which sub\-features are
actually present depend on the exact chip type.

The
.I sensors.conf
configuration file will let you configure each chip, feature and
sub\-feature in a way that makes sense for your system.

The rest of this section describes the meaning of each configuration
statement.

.SS CHIP STATEMENT

A
.I chip
statement selects for which chips all following
.IR compute ,
.IR label ,
.I ignore
and
.I set
statements are meant. A chip
selection remains valid until the next
.I chip
statement. Example:

.RS
chip "lm78\-*" "lm79\-*"
.RE

If a chip matches at least one of the chip descriptions, the following
configuration lines are examined for it, otherwise they are ignored.

A chip description is built from several elements, separated by
dashes. The first element is the chip type, the second element is
the name of the bus, and the third element is the hexadecimal address
of the chip. Such chip descriptions are printed by sensors(1) as the
first line for every chip.

The name of the bus is either
.IR isa ,
.IR pci ,
.IR virtual ,
.I spi-*,
.I i2c-N
or
.I mdio
with
.I N
being a bus number as bound with a
.I bus
statement. This list isn't necessarily exhaustive as support for other
bus types may be added in the future.

You may substitute the wildcard operator
.I *
for every element. Note however that it wouldn't make any sense to specify
the address without the bus type, so the address part is plain omitted
when the bus type isn't specified.
Here is how you would express the following matches:

.TS
l l.
LM78 chip at address 0x2d on I2C bus 1	lm78\-i2c\-1\-2d
LM78 chip at address 0x2d on any I2C bus	lm78\-i2c\-*\-2d
LM78 chip at address 0x290 on the ISA bus	lm78\-isa\-0290
Any LM78 chip on I2C bus 1	lm78\-i2c\-1\-*
Any LM78 on any I2C bus	lm78\-i2c\-*\-*
Any LM78 chip on the ISA bus	lm78\-isa\-*
Any LM78 chip	lm78\-*
Any chip at address 0x2d on I2C bus 1	*\-i2c\-1\-2d
Any chip at address 0x290 on the ISA bus	*\-isa\-0290
.TE

If several chip statements match a specific chip, they are all considered.

.SS LABEL STATEMENT

A
.I label
statement describes how a feature should be called. Features without a
.I label
statement are just called by their feature name. Applications can use this
to label the readings they present. Example:

.RS
label in3 "+5V"
.RE

The first argument is the feature name. The second argument is the feature
description.

Note that you must use the raw feature name, which is not necessarily the
one displayed by "sensors" by default. Use "sensors \-u" to see the raw
feature names. Same applies to all other statement types below.

.SS IGNORE STATEMENT

An
.I ignore
statement is a hint that a specific feature should be ignored - probably
because it returns bogus values (for example, because a fan or temperature
sensor is not connected). Example:

.RS
ignore fan1
.RE

The only argument is the feature name. Please note that this does not disable
anything in the actual sensor chip; it simply hides the feature in question
from libsensors users.

.SS COMPUTE STATEMENT

A
.I compute
statement describes how a feature's raw value should be translated to a
real\-world value, and how a real\-world value should be translated back
to a raw value again. This is most useful for voltage sensors, because
in general sensor chips have a limited range and voltages outside this
range must be divided (using resistors) before they can be monitored.
Example:

.RS
compute in3 ((6.8/10)+1)*@, @/((6.8/10)+1)
.RE

The example above expresses the fact that the voltage input is divided
using two resistors of values 6.8 Ohm and 10 Ohm, respectively. See the
.B VOLTAGE COMPUTATION DETAILS
section below for details.

The first argument is the feature name. The second argument is an expression
which specifies how a raw value must be translated to a real\-world value;
`@' stands here for the raw value. This is the formula which will be applied
when reading values from the chip. The third argument is an expression that
specifies how a real\-world value should be translated back to a raw value;
`@' stands here for the real\-world value. This is the formula which will be
applied when writing values to the chip. The two formulas are obviously
related, and are separated by a comma.

A
.I compute
statement applies to all sub\-features of the target feature for which
it makes sense. For example, the above example would affect sub\-features
in3_min and in3_max (which are voltage values) but not in3_alarm
(which is a boolean flag.)

The following operators are supported in
.I compute
statements:
.RS
+ \- * / ( ) ^ `
.RE
^x means exp(x) and `x means ln(x).

You may use the name of sub\-features in these expressions; current readings
are substituted. You should be careful though to avoid circular references.

If at any moment a translation between a raw and a real\-world value is
called for, but no
.I compute
statement applies, a one\-on\-one translation is used instead.

.SS SET STATEMENT

A
.I set
statement is used to write a sub\-feature value to the chip. Of course not
all sub\-feature values can be set that way, in particular input values
and alarm flags can not. Valid sub\-features are usually min/max limits.
Example:

.RS
set in3_min  5 * 0.95
.RE
.RS
set in3_max  5 * 1.05
.RE

The example above basically configures the chip to allow a 5% deviance
for the +5V power input.

The first argument is the feature name. The second argument is an expression
which determines the written value. If there is an applying
.I compute
statement, this value is fed to its third argument to translate it to a
raw value.

You may use the name of sub\-features in these expressions; current readings
are substituted. You should be careful though to avoid circular references.

Please note that
.I set
statements are only executed by sensors(1) when you use the
.B \-s
option. Typical graphical sensors applications do not care about these
statements at all.

.SS BUS STATEMENT

A
.I bus
statement binds the description of an I2C or SMBus adapter to a bus number.
This makes it possible to refer to an adapter in the configuration file,
independent of the actual correspondence of bus numbers and actual
adapters (which may change from moment to moment). Example:

.RS
bus "i2c\-0" "SMBus PIIX4 adapter at e800"
.RE

The first argument is the bus number. It is the literal text
.IR i2c\- ,
followed by a number. As there is a dash in this argument, it must
always be quoted.

The second argument is the adapter name, it must match exactly the
adapter name as it appears in
.IR /sys/class/i2c\-adapter/i2c\-*/name .
It should always be quoted as well as it will most certainly contain
spaces or dashes.

The
.I bus
statements may be scattered randomly throughout the configuration file;
there is no need to place the bus line before the place where its binding
is referred to. Still, as a matter of good style, we suggest you place
all
.I bus
statements together at the top of your configuration file.

Running
.B sensors --bus-list
will generate these lines for you.

In the case where multiple configuration files are used, the scope
of each
.I bus
statement is the configuration file it was defined in. This makes it
possible to have bus statements in all configuration files which will
not unexpectedly interfere with each other.

.SS STATEMENT ORDER

Statements can go in any order, however it is recommended to put
`set fanX_div' statements before `set fanX_min' statements, in case
a driver doesn't preserve the fanX_min setting when the fanX_div
value is changed. Even if the driver does, it's still better to put
the statements in this order to avoid accuracy loss.

.SH VOLTAGE COMPUTATION DETAILS

Most voltage sensors in sensor chips have a range of 0 to 4.08 V.
This is generally sufficient for the +3.3V and CPU supply voltages, so
the sensor chip reading is the actual voltage.

Other supply voltages must be scaled with an external resistor network.
The driver reports the value at the chip's pin (0 \- 4.08 V), and the
userspace application must convert this raw value to an actual voltage.
The
.I compute
statements provide this facility.

Unfortunately the resistor values vary among motherboard types.
Therefore you have to figure out the correct resistor values for your
own motherboard.

For positive voltages (typically +5V and +12V), two resistors are used,
with the following formula:
        R1 = R2 * (Vs/Vin \- 1)

where:
        R1 and R2 are the resistor values
        Vs is the actual voltage being monitored
        Vin is the voltage at the pin

This leads to the following compute formula:
        compute inX @*((R1/R2)+1),  @/(((R1/R2)+1)

Real\-world formula for +5V and +12V would look like:
        compute in3 @*((6.8/10)+1), @/((6.8/10)+1)
        compute in4 @*((28/10)+1),  @/((28/10)+1)

For negative voltages (typically \-5V and \-12V), two resistors are used
as well, but different boards use different strategies to bring the
voltage value into the 0 \- 4.08 V range. Some use an inverting
amplifier, others use a positive reference voltage. This leads to
different computation formulas. Note that most users won't have to care
because most modern motherboards make little use of \-12V and no use of
\-5V so they do not bother monitoring these voltage inputs.

Real\-world examples for the inverting amplifier case:
        compute in5 \-@*(240/60), \-@/(240/60)
        compute in6 \-@*(100/60), \-@/(100/60)

Real\-world examples for the positive voltage reference case:
        compute in5 @*(1+232/56) \- 4.096*232/56, (@ + 4.096*232/56)/(1+232/56)
        compute in6 @*(1+120/56) \- 4.096*120/56, (@ + 4.096*120/56)/(1+120/56)

Many recent monitoring chips have a 0 \- 2.04 V range, so scaling resistors
are even more needed, and resistor values are different.

There are also a few chips out there which have internal scaling
resistors, meaning that their value is known and doesn't change from
one motherboard to the next. For these chips, the driver usually
handles the scaling so it is transparent to the user and no
.I compute
statements are needed.

.SH TEMPERATURE CONFIGURATION

On top of the usual features, temperatures can have two specific
sub\-features: temperature sensor type (tempX_type) and hysteresis
values (tempX_max_hyst, tempX_crit_hyst etc.).

.SS THERMAL SENSOR TYPES

Available thermal sensor types:
.TS
r l.
1	PII/Celeron Diode
2	3904 transistor
3	thermal diode
4	thermistor
5	AMD AMDSI
6	Intel PECI
.TE

For example, to set temp1 to thermistor type, use:

.RS
set temp1_type 4
.RE

Only certain chips support thermal sensor type change, and even these
usually only support some of the types above. Please refer to the
specific driver documentation to find out which types are supported
by your chip.

In theory, the BIOS should have configured the sensor types correctly,
so you shouldn't have to touch them, but sometimes it isn't the case.

.SS THERMAL HYSTERESIS MECHANISM

Many monitoring chips do not handle the high and critical temperature
limits as simple limits. Instead, they have two values for each
limit, one which triggers an alarm when the temperature rises and another
one which clears the alarm when the temperature falls. The latter is
typically a few degrees below the former. This mechanism is known as
hysteresis.

The reason for implementing things that way is that high temperature
alarms typically trigger an action to attempt to cool the system down,
either by scaling down the CPU frequency, or by kicking in an extra
fan. This should normally let the temperature fall in a timely manner.
If this was clearing the alarm immediately, then the system would be
back to its original state where the temperature rises and the alarm
would immediately trigger again, causing an undesirable tight fan on,
fan off loop. The hysteresis mechanism ensures that the system is
really cool before the fan stops, so that it will not have to kick in
again immediately.

So, in addition to tempX_max, many chips have a tempX_max_hyst
sub-feature. Likewise, tempX_crit often comes with tempX_crit_hyst.
tempX_emerg_hyst, tempX_min_hyst and tempX_lcrit_hyst exist too but
aren't as common.
Example:

.RS
set temp1_max      60
.RE
.RS
set temp1_max_hyst 56
.RE

The hysteresis mechanism can be disabled by giving both limits the same
value.

Note that it is strongly recommended to set the hysteresis value after
the limit value it relates to in the configuration file. Implementation
details on the hardware or driver side may cause unexpected results if
the hysteresis value is set first.

.SH BEEPS

Some chips support alarms with beep warnings. When an alarm is triggered
you can be warned by a beeping signal through your computer speaker. On
top of per\-feature beep flags, there is usually a master beep control
switch to enable or disable beeping globally. Enable beeping using:

.RS
set beep_enable 1
.RE

or disable it using:

.RS
set beep_enable 0
.RE

.SH WHICH STATEMENT APPLIES

If more than one statement of the same kind applies at a certain moment,
the last one in the configuration file is used. So usually, you should
put more general
.I chip
statements at the top, so you can overrule them below.

.SH SYNTAX
Comments are introduced by hash marks. A comment continues to the end of the
line. Empty lines, and lines containing only whitespace or comments are
ignored.  Other lines have one of the below forms. There must be whitespace
between each element, but the amount of whitespace is unimportant. A line
may be continued on the next line by ending it with a backslash; this does
not work within a comment,
.B NAME
or
.BR NUMBER .

.RS
bus
.B NAME NAME NAME
.sp 0
chip
.B NAME\-LIST
.sp 0
label
.B NAME NAME
.sp 0
compute
.B NAME EXPR
,
.B EXPR
.sp 0
ignore
.B NAME
.sp 0
set
.B NAME EXPR
.RE
.sp
A
.B NAME
is a string. If it only contains letters, digits and underscores, it does not
have to be quoted; in all other cases, you must use double quotes around it.
Within quotes, you can use the normal escape\-codes from C.

A
.B NAME\-LIST
is one or more
.B NAME
items behind each other, separated by whitespace.

A
.B EXPR
is of one of the below forms:

.RS
.B NUMBER
.sp 0
.B NAME
.sp 0
@
.sp 0
.B EXPR
+
.B EXPR
.sp 0
.B EXPR
\-
.B EXPR
.sp 0
.B EXPR
*
.B EXPR
.sp 0
.B EXPR
/
.B EXPR
.sp 0
\-
.B EXPR
.sp 0
^
.B EXPR
.sp 0
`
.B EXPR
.sp 0
(
.B EXPR
)
.RE

A
.B NUMBER
is a floating\-point number. `10', `10.4' and `.4' are examples of valid
floating\-point numbers; `10.' or `10E4' are not valid.

.SH FILES
.I /etc/sensors3.conf
.br
.I /etc/sensors.conf
.RS
The system-wide
.BR libsensors (3)
configuration file. /etc/sensors3.conf is tried first, and if it doesn't exist,
/etc/sensors.conf is used instead.
.RE

.I /etc/sensors.d
.RS
A directory where you can put additional libsensors configuration files.
Files found in this directory will be processed in alphabetical order after
the default configuration file. Files with names that start with a dot are
ignored.
.RE

.SH SEE ALSO
libsensors(3)

.SH AUTHOR
Frodo Looijaard and the lm_sensors group
https://hwmon.wiki.kernel.org/lm_sensors