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1 | Naming and data format standards for sysfs files | ||
2 | ------------------------------------------------ | ||
3 | |||
4 | The libsensors library offers an interface to the raw sensors data | ||
5 | through the sysfs interface. See libsensors documentation and source for | ||
6 | more further information. As of writing this document, libsensors | ||
7 | (from lm_sensors 2.8.3) is heavily chip-dependant. Adding or updating | ||
8 | support for any given chip requires modifying the library's code. | ||
9 | This is because libsensors was written for the procfs interface | ||
10 | older kernel modules were using, which wasn't standardized enough. | ||
11 | Recent versions of libsensors (from lm_sensors 2.8.2 and later) have | ||
12 | support for the sysfs interface, though. | ||
13 | |||
14 | The new sysfs interface was designed to be as chip-independant as | ||
15 | possible. | ||
16 | |||
17 | Note that motherboards vary widely in the connections to sensor chips. | ||
18 | There is no standard that ensures, for example, that the second | ||
19 | temperature sensor is connected to the CPU, or that the second fan is on | ||
20 | the CPU. Also, some values reported by the chips need some computation | ||
21 | before they make full sense. For example, most chips can only measure | ||
22 | voltages between 0 and +4V. Other voltages are scaled back into that | ||
23 | range using external resistors. Since the values of these resistors | ||
24 | can change from motherboard to motherboard, the conversions cannot be | ||
25 | hard coded into the driver and have to be done in user space. | ||
26 | |||
27 | For this reason, even if we aim at a chip-independant libsensors, it will | ||
28 | still require a configuration file (e.g. /etc/sensors.conf) for proper | ||
29 | values conversion, labeling of inputs and hiding of unused inputs. | ||
30 | |||
31 | An alternative method that some programs use is to access the sysfs | ||
32 | files directly. This document briefly describes the standards that the | ||
33 | drivers follow, so that an application program can scan for entries and | ||
34 | access this data in a simple and consistent way. That said, such programs | ||
35 | will have to implement conversion, labeling and hiding of inputs. For | ||
36 | this reason, it is still not recommended to bypass the library. | ||
37 | |||
38 | If you are developing a userspace application please send us feedback on | ||
39 | this standard. | ||
40 | |||
41 | Note that this standard isn't completely established yet, so it is subject | ||
42 | to changes, even important ones. One more reason to use the library instead | ||
43 | of accessing sysfs files directly. | ||
44 | |||
45 | Each chip gets its own directory in the sysfs /sys/devices tree. To | ||
46 | find all sensor chips, it is easier to follow the symlinks from | ||
47 | /sys/i2c/devices/ | ||
48 | |||
49 | All sysfs values are fixed point numbers. To get the true value of some | ||
50 | of the values, you should divide by the specified value. | ||
51 | |||
52 | There is only one value per file, unlike the older /proc specification. | ||
53 | The common scheme for files naming is: <type><number>_<item>. Usual | ||
54 | types for sensor chips are "in" (voltage), "temp" (temperature) and | ||
55 | "fan" (fan). Usual items are "input" (measured value), "max" (high | ||
56 | threshold, "min" (low threshold). Numbering usually starts from 1, | ||
57 | except for voltages which start from 0 (because most data sheets use | ||
58 | this). A number is always used for elements that can be present more | ||
59 | than once, even if there is a single element of the given type on the | ||
60 | specific chip. Other files do not refer to a specific element, so | ||
61 | they have a simple name, and no number. | ||
62 | |||
63 | Alarms are direct indications read from the chips. The drivers do NOT | ||
64 | make comparisons of readings to thresholds. This allows violations | ||
65 | between readings to be caught and alarmed. The exact definition of an | ||
66 | alarm (for example, whether a threshold must be met or must be exceeded | ||
67 | to cause an alarm) is chip-dependent. | ||
68 | |||
69 | |||
70 | ------------------------------------------------------------------------- | ||
71 | |||
72 | ************ | ||
73 | * Voltages * | ||
74 | ************ | ||
75 | |||
76 | in[0-8]_min Voltage min value. | ||
77 | Unit: millivolt | ||
78 | Read/Write | ||
79 | |||
80 | in[0-8]_max Voltage max value. | ||
81 | Unit: millivolt | ||
82 | Read/Write | ||
83 | |||
84 | in[0-8]_input Voltage input value. | ||
85 | Unit: millivolt | ||
86 | Read only | ||
87 | Actual voltage depends on the scaling resistors on the | ||
88 | motherboard, as recommended in the chip datasheet. | ||
89 | This varies by chip and by motherboard. | ||
90 | Because of this variation, values are generally NOT scaled | ||
91 | by the chip driver, and must be done by the application. | ||
92 | However, some drivers (notably lm87 and via686a) | ||
93 | do scale, with various degrees of success. | ||
94 | These drivers will output the actual voltage. | ||
95 | |||
96 | Typical usage: | ||
97 | in0_* CPU #1 voltage (not scaled) | ||
98 | in1_* CPU #2 voltage (not scaled) | ||
99 | in2_* 3.3V nominal (not scaled) | ||
100 | in3_* 5.0V nominal (scaled) | ||
101 | in4_* 12.0V nominal (scaled) | ||
102 | in5_* -12.0V nominal (scaled) | ||
103 | in6_* -5.0V nominal (scaled) | ||
104 | in7_* varies | ||
105 | in8_* varies | ||
106 | |||
107 | cpu[0-1]_vid CPU core reference voltage. | ||
108 | Unit: millivolt | ||
109 | Read only. | ||
110 | Not always correct. | ||
111 | |||
112 | vrm Voltage Regulator Module version number. | ||
113 | Read only. | ||
114 | Two digit number, first is major version, second is | ||
115 | minor version. | ||
116 | Affects the way the driver calculates the CPU core reference | ||
117 | voltage from the vid pins. | ||
118 | |||
119 | |||
120 | ******** | ||
121 | * Fans * | ||
122 | ******** | ||
123 | |||
124 | fan[1-3]_min Fan minimum value | ||
125 | Unit: revolution/min (RPM) | ||
126 | Read/Write. | ||
127 | |||
128 | fan[1-3]_input Fan input value. | ||
129 | Unit: revolution/min (RPM) | ||
130 | Read only. | ||
131 | |||
132 | fan[1-3]_div Fan divisor. | ||
133 | Integer value in powers of two (1, 2, 4, 8, 16, 32, 64, 128). | ||
134 | Some chips only support values 1, 2, 4 and 8. | ||
135 | Note that this is actually an internal clock divisor, which | ||
136 | affects the measurable speed range, not the read value. | ||
137 | |||
138 | ******* | ||
139 | * PWM * | ||
140 | ******* | ||
141 | |||
142 | pwm[1-3] Pulse width modulation fan control. | ||
143 | Integer value in the range 0 to 255 | ||
144 | Read/Write | ||
145 | 255 is max or 100%. | ||
146 | |||
147 | pwm[1-3]_enable | ||
148 | Switch PWM on and off. | ||
149 | Not always present even if fan*_pwm is. | ||
150 | 0 to turn off | ||
151 | 1 to turn on in manual mode | ||
152 | 2 to turn on in automatic mode | ||
153 | Read/Write | ||
154 | |||
155 | pwm[1-*]_auto_channels_temp | ||
156 | Select which temperature channels affect this PWM output in | ||
157 | auto mode. Bitfield, 1 is temp1, 2 is temp2, 4 is temp3 etc... | ||
158 | Which values are possible depend on the chip used. | ||
159 | |||
160 | pwm[1-*]_auto_point[1-*]_pwm | ||
161 | pwm[1-*]_auto_point[1-*]_temp | ||
162 | pwm[1-*]_auto_point[1-*]_temp_hyst | ||
163 | Define the PWM vs temperature curve. Number of trip points is | ||
164 | chip-dependent. Use this for chips which associate trip points | ||
165 | to PWM output channels. | ||
166 | |||
167 | OR | ||
168 | |||
169 | temp[1-*]_auto_point[1-*]_pwm | ||
170 | temp[1-*]_auto_point[1-*]_temp | ||
171 | temp[1-*]_auto_point[1-*]_temp_hyst | ||
172 | Define the PWM vs temperature curve. Number of trip points is | ||
173 | chip-dependent. Use this for chips which associate trip points | ||
174 | to temperature channels. | ||
175 | |||
176 | |||
177 | **************** | ||
178 | * Temperatures * | ||
179 | **************** | ||
180 | |||
181 | temp[1-3]_type Sensor type selection. | ||
182 | Integers 1, 2, 3 or thermistor Beta value (3435) | ||
183 | Read/Write. | ||
184 | 1: PII/Celeron Diode | ||
185 | 2: 3904 transistor | ||
186 | 3: thermal diode | ||
187 | Not all types are supported by all chips | ||
188 | |||
189 | temp[1-4]_max Temperature max value. | ||
190 | Unit: millidegree Celcius | ||
191 | Read/Write value. | ||
192 | |||
193 | temp[1-3]_min Temperature min value. | ||
194 | Unit: millidegree Celcius | ||
195 | Read/Write value. | ||
196 | |||
197 | temp[1-3]_max_hyst | ||
198 | Temperature hysteresis value for max limit. | ||
199 | Unit: millidegree Celcius | ||
200 | Must be reported as an absolute temperature, NOT a delta | ||
201 | from the max value. | ||
202 | Read/Write value. | ||
203 | |||
204 | temp[1-4]_input Temperature input value. | ||
205 | Unit: millidegree Celcius | ||
206 | Read only value. | ||
207 | |||
208 | temp[1-4]_crit Temperature critical value, typically greater than | ||
209 | corresponding temp_max values. | ||
210 | Unit: millidegree Celcius | ||
211 | Read/Write value. | ||
212 | |||
213 | temp[1-2]_crit_hyst | ||
214 | Temperature hysteresis value for critical limit. | ||
215 | Unit: millidegree Celcius | ||
216 | Must be reported as an absolute temperature, NOT a delta | ||
217 | from the critical value. | ||
218 | Read/Write value. | ||
219 | |||
220 | If there are multiple temperature sensors, temp1_* is | ||
221 | generally the sensor inside the chip itself, | ||
222 | reported as "motherboard temperature". temp2_* to | ||
223 | temp4_* are generally sensors external to the chip | ||
224 | itself, for example the thermal diode inside the CPU or | ||
225 | a thermistor nearby. | ||
226 | |||
227 | |||
228 | ************ | ||
229 | * Currents * | ||
230 | ************ | ||
231 | |||
232 | Note that no known chip provides current measurements as of writing, | ||
233 | so this part is theoretical, so to say. | ||
234 | |||
235 | curr[1-n]_max Current max value | ||
236 | Unit: milliampere | ||
237 | Read/Write. | ||
238 | |||
239 | curr[1-n]_min Current min value. | ||
240 | Unit: milliampere | ||
241 | Read/Write. | ||
242 | |||
243 | curr[1-n]_input Current input value | ||
244 | Unit: milliampere | ||
245 | Read only. | ||
246 | |||
247 | |||
248 | ********* | ||
249 | * Other * | ||
250 | ********* | ||
251 | |||
252 | alarms Alarm bitmask. | ||
253 | Read only. | ||
254 | Integer representation of one to four bytes. | ||
255 | A '1' bit means an alarm. | ||
256 | Chips should be programmed for 'comparator' mode so that | ||
257 | the alarm will 'come back' after you read the register | ||
258 | if it is still valid. | ||
259 | Generally a direct representation of a chip's internal | ||
260 | alarm registers; there is no standard for the position | ||
261 | of individual bits. | ||
262 | Bits are defined in kernel/include/sensors.h. | ||
263 | |||
264 | beep_enable Beep/interrupt enable | ||
265 | 0 to disable. | ||
266 | 1 to enable. | ||
267 | Read/Write | ||
268 | |||
269 | beep_mask Bitmask for beep. | ||
270 | Same format as 'alarms' with the same bit locations. | ||
271 | Read/Write | ||
272 | |||
273 | eeprom Raw EEPROM data in binary form. | ||
274 | Read only. | ||