------------------------------------------------
The libsensors library offers an interface to the raw sensors data
-through the sysfs interface. See libsensors documentation and source for
-further information. As of writing this document, libsensors
-(from lm_sensors 2.8.3) is heavily chip-dependent. 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-independent 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
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. If you are writing a new hardware monitoring driver those
-features can't seem to fit in this interface, please contact us with your
-extension proposal. Keep in mind that backward compatibility must be
-preserved.
-
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.
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.
-------------------------------------------------------------------------
Read/write values may be read-only for some chips, depending on the
hardware implementation.
-All entries are optional, and should only be created in a given driver
-if the chip has the feature.
+All entries (except name) are optional, and should only be created in a
+given driver if the chip has the feature.
+
+
+********
+* Name *
+********
+
+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
+
************
* 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
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.
****************
temp[1-*]_type Sensor type selection.
- Integers 1 to 6 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
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
Some chips measure temperature using external thermistors and an ADC, and
report the temperature measurement as a voltage. Converting this voltage
Unit: milliampere
RO
+*********
+* Power *
+*********
+
+power[1-*]_average Average power use
+ Unit: microWatt
+ 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-*]_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
**********
* Alarms *
RW
-*********
-* Other *
-*********
-
-eeprom Raw EEPROM data in binary form.
- RO
-
-pec Enable or disable PEC (SMBus only)
- 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 */
git.openpandora.org / pandora-kernel.git / blobdiff