[PATCH] hwmon: Sysfs interface documentation update, 2 of 2, take 2
Reword and complete certain parts of the hwmon sysfs-interface documentation file. Hopefully this will make things clearer for new driver authors. Signed-off-by: Jean Delvare <khali@linux-fr.org> Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
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@ -3,15 +3,15 @@ Naming and data format standards for sysfs files
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The libsensors library offers an interface to the raw sensors data
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through the sysfs interface. See libsensors documentation and source for
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more further information. As of writing this document, libsensors
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(from lm_sensors 2.8.3) is heavily chip-dependant. Adding or updating
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further information. As of writing this document, libsensors
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(from lm_sensors 2.8.3) is heavily chip-dependent. Adding or updating
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support for any given chip requires modifying the library's code.
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This is because libsensors was written for the procfs interface
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older kernel modules were using, which wasn't standardized enough.
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Recent versions of libsensors (from lm_sensors 2.8.2 and later) have
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support for the sysfs interface, though.
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The new sysfs interface was designed to be as chip-independant as
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The new sysfs interface was designed to be as chip-independent as
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possible.
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Note that motherboards vary widely in the connections to sensor chips.
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@ -24,7 +24,7 @@ range using external resistors. Since the values of these resistors
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can change from motherboard to motherboard, the conversions cannot be
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hard coded into the driver and have to be done in user space.
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For this reason, even if we aim at a chip-independant libsensors, it will
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For this reason, even if we aim at a chip-independent libsensors, it will
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still require a configuration file (e.g. /etc/sensors.conf) for proper
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values conversion, labeling of inputs and hiding of unused inputs.
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@ -39,15 +39,16 @@ If you are developing a userspace application please send us feedback on
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this standard.
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Note that this standard isn't completely established yet, so it is subject
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to changes, even important ones. One more reason to use the library instead
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of accessing sysfs files directly.
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to changes. If you are writing a new hardware monitoring driver those
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features can't seem to fit in this interface, please contact us with your
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extension proposal. Keep in mind that backward compatibility must be
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preserved.
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Each chip gets its own directory in the sysfs /sys/devices tree. To
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find all sensor chips, it is easier to follow the symlinks from
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/sys/i2c/devices/
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find all sensor chips, it is easier to follow the device symlinks from
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/sys/class/hwmon/hwmon*.
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All sysfs values are fixed point numbers. To get the true value of some
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of the values, you should divide by the specified value.
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All sysfs values are fixed point numbers.
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There is only one value per file, unlike the older /proc specification.
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The common scheme for files naming is: <type><number>_<item>. Usual
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@ -77,6 +78,9 @@ RW read/write value
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Read/write values may be read-only for some chips, depending on the
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hardware implementation.
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All entries are optional, and should only be created in a given driver
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if the chip has the feature.
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************
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* Voltages *
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************
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@ -213,32 +217,32 @@ temp[1-*]_type Sensor type selection.
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Not all types are supported by all chips
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temp[1-*]_max Temperature max value.
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Unit: millidegree Celcius
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Unit: millidegree Celsius (or millivolt, see below)
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RW
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temp[1-*]_min Temperature min value.
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Unit: millidegree Celcius
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Unit: millidegree Celsius
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RW
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temp[1-*]_max_hyst
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Temperature hysteresis value for max limit.
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Unit: millidegree Celcius
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Unit: millidegree Celsius
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Must be reported as an absolute temperature, NOT a delta
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from the max value.
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RW
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temp[1-*]_input Temperature input value.
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Unit: millidegree Celcius
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Unit: millidegree Celsius
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RO
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temp[1-*]_crit Temperature critical value, typically greater than
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corresponding temp_max values.
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Unit: millidegree Celcius
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Unit: millidegree Celsius
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RW
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temp[1-*]_crit_hyst
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Temperature hysteresis value for critical limit.
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Unit: millidegree Celcius
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Unit: millidegree Celsius
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Must be reported as an absolute temperature, NOT a delta
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from the critical value.
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RW
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@ -256,6 +260,15 @@ temp[1-4]_offset
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itself, for example the thermal diode inside the CPU or
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a thermistor nearby.
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Some chips measure temperature using external thermistors and an ADC, and
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report the temperature measurement as a voltage. Converting this voltage
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back to a temperature (or the other way around for limits) requires
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mathematical functions not available in the kernel, so the conversion
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must occur in user space. For these chips, all temp* files described
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above should contain values expressed in millivolt instead of millidegree
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Celsius. In other words, such temperature channels are handled as voltage
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channels by the driver.
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Also see the Alarms section for status flags associated with temperatures.
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