Hi all, Below is a proposed update of the sysfs-interface document. I'd like to hear comments about it. I do not post it as a patch because it's not easily readable due to structure changes. I better describe the changes: * I expose our goals for the new interface and the possible new library (chip-independancy). * I explain why bypassing the library is not a good idea and why a library is still needed even with a chip-independant sysfs files naming scheme. * I describe the files naming scheme. Note that I still don't like it, as mentioned in a previous post: http://archives.andrew.net.au/lm-sensors/msg06206.html BTW I did not have a single answer and am a bit sad about that. I think this is something important and I wouldn't want to change things unless at least someone agrees it is not too bad an idea. * In the files list, I group the entries by categories. I think this is easier to read for the newcomer. I plan to reword the files descriptions as well, but this is a different story. And I still plan to make real changes to the interface. But that's a different story again. And I would also want to add entries present in the fscher and gl518fs drivers that are not described in the document yet. Another story again. Thanks. Naming and data format standards for sysfs files ------------------------------------------------ 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. 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-independant 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. 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/ All sysfs values are fixed point numbers. To get the true value of some of the values, you should divide by the specified value. There is only one value per file, unlike the older /proc specification. The common scheme for files naming is: <type>_<item><number>. 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. ------------------------------------------------------------------------- ************ * Voltages * ************ in_min[0-8] Voltage min value. Fixed point value in form XXXX. Divide by 1000 to get Volts. Read/Write in_max[0-8] Voltage max value. Fixed point value in form XXXX. Divide by 1000 to get Volts. Read/Write in_input[0-8] Voltage input value. Fixed point value in form XXXX. Divide by 1000 to get Volts. Read only 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, with various degrees of success. These drivers will output the actual voltage. First two values are read/write and third is read only. Typical usage: in_*0 CPU #1 voltage (not scaled) in_*1 CPU #1 voltage (not scaled) in_*2 3.3V nominal (not scaled) in_*3 5.0V nominal (scaled) in_*4 12.0V nominal (scaled) in_*5 -12.0V nominal (scaled) in_*6 -5.0V nominal (scaled) in_*7 varies in_*8 varies vid CPU core voltage. Read only. Fixed point value in form XXXX corresponding to CPU core voltage as told to the sensor chip. Divide by 1000 to get Volts. Not always correct. vrm Voltage Regulator Module version number. Read only. Two digit number (XX), first is major version, second is minor version. Affects the way the driver calculates the core voltage from the vid pins. See doc/vid for details. ******** * Fans * ******** fan_min[1-3] Fan minimum value Integer value indicating RPM Read/Write. fan_input[1-3] Fan input value. Integer value indicating RPM Read only. fan_div[1-3] Fan divisor. Integers in powers of two (1,2,4,8,16,32,64,128). Some chips only support values 1,2,4,8. See doc/fan-divisors for details. pwm[1-3] Pulse width modulation fan control. Integer 0 - 255 Read/Write 255 is max or 100%. Corresponds to the fans 1-3. pwm_enable[1-3] pwm enable not always present even if pwm* is. 0 to turn off 1 to turn on Read/Write **************** * Temperatures * **************** sensor[1-3] Sensor type selection. Integers 1,2,3, or thermistor Beta value (3435) Read/Write. temp_max[1-4] Temperature max value. Fixed point value in form XXXXX and should be divided by 1000 to get degrees Celsius. Read/Write value. temp_min[1-3] Temperature min value. Fixed point value in form XXXXX and should be divided by 1000 to get degrees Celsius. Read/Write value. temp_hyst[1-3] Temperature hysteresis value. Fixed point value in form XXXXX and should be divided by 1000 to get degrees Celsius. Must be reported as an absolute temperature, NOT a delta from the max value. Read/Write value. temp_input[1-4] Temperature input value. Fixed point value in form XXXXX and should be divided by 1000 to get degrees Celsius. Read only value. temp_crit Temperature critical value, typically greater than all temp_max values. Fixed point value in form XXXXX and should be divided by 1000 to get degrees Celsius. Common to all temperature channels. Read/Write value. If there are multiple temperature sensors, temp_*1 is generally the sensor inside the chip itself, generally reported as "motherboard temperature". temp_*2 to temp_*4 are generally sensors external to the chip itself, for example the thermal diode inside the CPU or a thermistor nearby. ************ * Currents * ************ Note that no known chip provides current measurements as of writing, so this part is theoretical, so to say. curr_max[1-n] Current max value Fixed point XXXXX, divide by 1000 to get Amps. Read/Write. curr_min[1-n] Current min value. Fixed point XXXXX, divide by 1000 to get Amps. Read/Write. curr_input[1-n] Current input value Fixed point XXXXX, divide by 1000 to get Amps. Read only. ********* * Other * ********* alarms Alarm bitmask. Read only. 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. Bits are defined in kernel/include/sensors.h. beep_enable Beep/interrupt enable 0 to disable. 1 to enable. Read/Write beep_mask Bitmask for beep. Same format as 'alarms' with the same bit locations. Read only. eeprom Raw EEPROM data in binary form. Read only. -- Jean Delvare http://www.ensicaen.ismra.fr/~delvare/
