mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-08-21 16:29:59 +00:00
![Guenter Roeck](/assets/img/avatar_default.png)
The attribute reflects an interval, not a rate. Signed-off-by: Guenter Roeck <guenter.roeck@ericsson.com> Acked-by: Ira W. Snyder <iws@ovro.caltech.edu> Signed-off-by: Jean Delvare <khali@linux-fr.org>
639 lines
19 KiB
Text
639 lines
19 KiB
Text
Naming and data format standards for sysfs files
|
|
------------------------------------------------
|
|
|
|
The libsensors library offers an interface to the raw sensors data
|
|
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
|
|
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-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.
|
|
|
|
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.
|
|
|
|
Each chip gets its own directory in the sysfs /sys/devices tree. To
|
|
find 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 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
|
|
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.
|
|
|
|
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_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-*]_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-*]_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-*]_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.
|
|
RW
|
|
|
|
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.
|
|
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 6
|
|
RW
|
|
1: PII/Celeron 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-*]_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, 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.
|
|
|
|
|
|
************
|
|
* Currents *
|
|
************
|
|
|
|
curr[1-*]_max Current max value
|
|
Unit: milliampere
|
|
RW
|
|
|
|
curr[1-*]_min Current min value.
|
|
Unit: milliampere
|
|
RW
|
|
|
|
curr[1-*]_input Current input value
|
|
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 *
|
|
**********
|
|
|
|
Each channel or limit may have an associated alarm file, containing a
|
|
boolean value. 1 means than an alarm condition exists, 0 means no alarm.
|
|
|
|
Usually a given chip will either use channel-related alarms, or
|
|
limit-related alarms, not both. The driver should just reflect the hardware
|
|
implementation.
|
|
|
|
in[0-*]_alarm
|
|
curr[1-*]_alarm
|
|
fan[1-*]_alarm
|
|
temp[1-*]_alarm
|
|
Channel alarm
|
|
0: no alarm
|
|
1: alarm
|
|
RO
|
|
|
|
OR
|
|
|
|
in[0-*]_min_alarm
|
|
in[0-*]_max_alarm
|
|
curr[1-*]_min_alarm
|
|
curr[1-*]_max_alarm
|
|
fan[1-*]_min_alarm
|
|
fan[1-*]_max_alarm
|
|
temp[1-*]_min_alarm
|
|
temp[1-*]_max_alarm
|
|
temp[1-*]_crit_alarm
|
|
Limit alarm
|
|
0: no alarm
|
|
1: alarm
|
|
RO
|
|
|
|
Each input channel may have an associated fault file. This can be used
|
|
to notify open diodes, unconnected fans etc. where the hardware
|
|
supports it. When this boolean has value 1, the measurement for that
|
|
channel should not be trusted.
|
|
|
|
fan[1-*]_fault
|
|
temp[1-*]_fault
|
|
Input fault condition
|
|
0: no fault occured
|
|
1: fault condition
|
|
RO
|
|
|
|
Some chips also offer the possibility to get beeped when an alarm occurs:
|
|
|
|
beep_enable Master beep enable
|
|
0: no beeps
|
|
1: beeps
|
|
RW
|
|
|
|
in[0-*]_beep
|
|
curr[1-*]_beep
|
|
fan[1-*]_beep
|
|
temp[1-*]_beep
|
|
Channel beep
|
|
0: disable
|
|
1: enable
|
|
RW
|
|
|
|
In theory, a chip could provide per-limit beep masking, but no such chip
|
|
was seen so far.
|
|
|
|
Old drivers provided a different, non-standard interface to alarms and
|
|
beeps. These interface files are deprecated, but will be kept around
|
|
for compatibility reasons:
|
|
|
|
alarms Alarm bitmask.
|
|
RO
|
|
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. For this reason, the use of this
|
|
interface file for new drivers is discouraged. Use
|
|
individual *_alarm and *_fault files instead.
|
|
Bits are defined in kernel/include/sensors.h.
|
|
|
|
beep_mask Bitmask for beep.
|
|
Same format as 'alarms' with the same bit locations,
|
|
use discouraged for the same reason. Use individual
|
|
*_beep files instead.
|
|
RW
|
|
|
|
|
|
***********************
|
|
* Intrusion detection *
|
|
***********************
|
|
|
|
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.
|
|
|
|
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 */
|