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1da177e4 LT |
1 | Naming and data format standards for sysfs files |
2 | ------------------------------------------------ | |
3 | ||
4 | The libsensors library offers an interface to the raw sensors data | |
125ff808 JD |
5 | through the sysfs interface. Since lm-sensors 3.0.0, libsensors is |
6 | completely chip-independent. It assumes that all the kernel drivers | |
7 | implement the standard sysfs interface described in this document. | |
8 | This makes adding or updating support for any given chip very easy, as | |
9 | libsensors, and applications using it, do not need to be modified. | |
10 | This is a major improvement compared to lm-sensors 2. | |
1da177e4 LT |
11 | |
12 | Note that motherboards vary widely in the connections to sensor chips. | |
13 | There is no standard that ensures, for example, that the second | |
14 | temperature sensor is connected to the CPU, or that the second fan is on | |
15 | the CPU. Also, some values reported by the chips need some computation | |
16 | before they make full sense. For example, most chips can only measure | |
17 | voltages between 0 and +4V. Other voltages are scaled back into that | |
18 | range using external resistors. Since the values of these resistors | |
19 | can change from motherboard to motherboard, the conversions cannot be | |
20 | hard coded into the driver and have to be done in user space. | |
21 | ||
740e06a8 | 22 | For this reason, even if we aim at a chip-independent libsensors, it will |
1da177e4 LT |
23 | still require a configuration file (e.g. /etc/sensors.conf) for proper |
24 | values conversion, labeling of inputs and hiding of unused inputs. | |
25 | ||
26 | An alternative method that some programs use is to access the sysfs | |
27 | files directly. This document briefly describes the standards that the | |
28 | drivers follow, so that an application program can scan for entries and | |
29 | access this data in a simple and consistent way. That said, such programs | |
30 | will have to implement conversion, labeling and hiding of inputs. For | |
31 | this reason, it is still not recommended to bypass the library. | |
32 | ||
1da177e4 | 33 | Each chip gets its own directory in the sysfs /sys/devices tree. To |
740e06a8 JD |
34 | find all sensor chips, it is easier to follow the device symlinks from |
35 | /sys/class/hwmon/hwmon*. | |
1da177e4 | 36 | |
125ff808 JD |
37 | Up to lm-sensors 3.0.0, libsensors looks for hardware monitoring attributes |
38 | in the "physical" device directory. Since lm-sensors 3.0.1, attributes found | |
39 | in the hwmon "class" device directory are also supported. Complex drivers | |
40 | (e.g. drivers for multifunction chips) may want to use this possibility to | |
41 | avoid namespace pollution. The only drawback will be that older versions of | |
42 | libsensors won't support the driver in question. | |
43 | ||
740e06a8 | 44 | All sysfs values are fixed point numbers. |
1da177e4 LT |
45 | |
46 | There is only one value per file, unlike the older /proc specification. | |
47 | The common scheme for files naming is: <type><number>_<item>. Usual | |
48 | types for sensor chips are "in" (voltage), "temp" (temperature) and | |
49 | "fan" (fan). Usual items are "input" (measured value), "max" (high | |
50 | threshold, "min" (low threshold). Numbering usually starts from 1, | |
51 | except for voltages which start from 0 (because most data sheets use | |
52 | this). A number is always used for elements that can be present more | |
53 | than once, even if there is a single element of the given type on the | |
54 | specific chip. Other files do not refer to a specific element, so | |
55 | they have a simple name, and no number. | |
56 | ||
57 | Alarms are direct indications read from the chips. The drivers do NOT | |
58 | make comparisons of readings to thresholds. This allows violations | |
59 | between readings to be caught and alarmed. The exact definition of an | |
60 | alarm (for example, whether a threshold must be met or must be exceeded | |
61 | to cause an alarm) is chip-dependent. | |
62 | ||
2ed42633 HG |
63 | When setting values of hwmon sysfs attributes, the string representation of |
64 | the desired value must be written, note that strings which are not a number | |
65 | are interpreted as 0! For more on how written strings are interpreted see the | |
66 | "sysfs attribute writes interpretation" section at the end of this file. | |
1da177e4 LT |
67 | |
68 | ------------------------------------------------------------------------- | |
69 | ||
057bc350 RM |
70 | [0-*] denotes any positive number starting from 0 |
71 | [1-*] denotes any positive number starting from 1 | |
72 | RO read only value | |
cd4e96c5 | 73 | WO write only value |
057bc350 RM |
74 | RW read/write value |
75 | ||
76 | Read/write values may be read-only for some chips, depending on the | |
77 | hardware implementation. | |
78 | ||
176544dc JD |
79 | All entries (except name) are optional, and should only be created in a |
80 | given driver if the chip has the feature. | |
81 | ||
82 | ||
83 | ******** | |
84 | * Name * | |
85 | ******** | |
86 | ||
87 | name The chip name. | |
88 | This should be a short, lowercase string, not containing | |
89 | spaces nor dashes, representing the chip name. This is | |
90 | the only mandatory attribute. | |
91 | I2C devices get this attribute created automatically. | |
92 | RO | |
93 | ||
740e06a8 | 94 | |
1da177e4 LT |
95 | ************ |
96 | * Voltages * | |
97 | ************ | |
98 | ||
057bc350 | 99 | in[0-*]_min Voltage min value. |
1da177e4 | 100 | Unit: millivolt |
057bc350 | 101 | RW |
1da177e4 | 102 | |
057bc350 | 103 | in[0-*]_max Voltage max value. |
1da177e4 | 104 | Unit: millivolt |
057bc350 | 105 | RW |
1da177e4 | 106 | |
057bc350 | 107 | in[0-*]_input Voltage input value. |
1da177e4 | 108 | Unit: millivolt |
057bc350 RM |
109 | RO |
110 | Voltage measured on the chip pin. | |
1da177e4 LT |
111 | Actual voltage depends on the scaling resistors on the |
112 | motherboard, as recommended in the chip datasheet. | |
113 | This varies by chip and by motherboard. | |
114 | Because of this variation, values are generally NOT scaled | |
115 | by the chip driver, and must be done by the application. | |
116 | However, some drivers (notably lm87 and via686a) | |
057bc350 | 117 | do scale, because of internal resistors built into a chip. |
176544dc JD |
118 | These drivers will output the actual voltage. Rule of |
119 | thumb: drivers should report the voltage values at the | |
120 | "pins" of the chip. | |
121 | ||
122 | in[0-*]_label Suggested voltage channel label. | |
123 | Text string | |
124 | Should only be created if the driver has hints about what | |
125 | this voltage channel is being used for, and user-space | |
126 | doesn't. In all other cases, the label is provided by | |
127 | user-space. | |
128 | RO | |
1da177e4 | 129 | |
057bc350 | 130 | cpu[0-*]_vid CPU core reference voltage. |
1da177e4 | 131 | Unit: millivolt |
057bc350 | 132 | RO |
1da177e4 LT |
133 | Not always correct. |
134 | ||
135 | vrm Voltage Regulator Module version number. | |
057bc350 RM |
136 | RW (but changing it should no more be necessary) |
137 | Originally the VRM standard version multiplied by 10, but now | |
138 | an arbitrary number, as not all standards have a version | |
139 | number. | |
1da177e4 LT |
140 | Affects the way the driver calculates the CPU core reference |
141 | voltage from the vid pins. | |
142 | ||
057bc350 RM |
143 | Also see the Alarms section for status flags associated with voltages. |
144 | ||
1da177e4 LT |
145 | |
146 | ******** | |
147 | * Fans * | |
148 | ******** | |
149 | ||
057bc350 | 150 | fan[1-*]_min Fan minimum value |
1da177e4 | 151 | Unit: revolution/min (RPM) |
057bc350 | 152 | RW |
1da177e4 | 153 | |
d54d4624 CE |
154 | fan[1-*]_max Fan maximum value |
155 | Unit: revolution/min (RPM) | |
156 | Only rarely supported by the hardware. | |
157 | RW | |
158 | ||
057bc350 | 159 | fan[1-*]_input Fan input value. |
1da177e4 | 160 | Unit: revolution/min (RPM) |
057bc350 | 161 | RO |
1da177e4 | 162 | |
057bc350 | 163 | fan[1-*]_div Fan divisor. |
1da177e4 | 164 | Integer value in powers of two (1, 2, 4, 8, 16, 32, 64, 128). |
057bc350 | 165 | RW |
1da177e4 LT |
166 | Some chips only support values 1, 2, 4 and 8. |
167 | Note that this is actually an internal clock divisor, which | |
168 | affects the measurable speed range, not the read value. | |
169 | ||
2dbc514a JD |
170 | fan[1-*]_target |
171 | Desired fan speed | |
172 | Unit: revolution/min (RPM) | |
173 | RW | |
174 | Only makes sense if the chip supports closed-loop fan speed | |
175 | control based on the measured fan speed. | |
176 | ||
176544dc JD |
177 | fan[1-*]_label Suggested fan channel label. |
178 | Text string | |
179 | Should only be created if the driver has hints about what | |
180 | this fan channel is being used for, and user-space doesn't. | |
181 | In all other cases, the label is provided by user-space. | |
182 | RO | |
183 | ||
057bc350 RM |
184 | Also see the Alarms section for status flags associated with fans. |
185 | ||
186 | ||
1da177e4 LT |
187 | ******* |
188 | * PWM * | |
189 | ******* | |
190 | ||
057bc350 | 191 | pwm[1-*] Pulse width modulation fan control. |
1da177e4 | 192 | Integer value in the range 0 to 255 |
057bc350 | 193 | RW |
1da177e4 LT |
194 | 255 is max or 100%. |
195 | ||
057bc350 | 196 | pwm[1-*]_enable |
875f25d5 JD |
197 | Fan speed control method: |
198 | 0: no fan speed control (i.e. fan at full speed) | |
199 | 1: manual fan speed control enabled (using pwm[1-*]) | |
200 | 2+: automatic fan speed control enabled | |
f8d0c19a JD |
201 | Check individual chip documentation files for automatic mode |
202 | details. | |
057bc350 RM |
203 | RW |
204 | ||
f8d0c19a JD |
205 | pwm[1-*]_mode 0: DC mode (direct current) |
206 | 1: PWM mode (pulse-width modulation) | |
207 | RW | |
208 | ||
209 | pwm[1-*]_freq Base PWM frequency in Hz. | |
210 | Only possibly available when pwmN_mode is PWM, but not always | |
211 | present even then. | |
057bc350 | 212 | RW |
1da177e4 LT |
213 | |
214 | pwm[1-*]_auto_channels_temp | |
215 | Select which temperature channels affect this PWM output in | |
216 | auto mode. Bitfield, 1 is temp1, 2 is temp2, 4 is temp3 etc... | |
217 | Which values are possible depend on the chip used. | |
057bc350 | 218 | RW |
1da177e4 LT |
219 | |
220 | pwm[1-*]_auto_point[1-*]_pwm | |
221 | pwm[1-*]_auto_point[1-*]_temp | |
222 | pwm[1-*]_auto_point[1-*]_temp_hyst | |
223 | Define the PWM vs temperature curve. Number of trip points is | |
224 | chip-dependent. Use this for chips which associate trip points | |
225 | to PWM output channels. | |
057bc350 | 226 | RW |
1da177e4 | 227 | |
1da177e4 LT |
228 | temp[1-*]_auto_point[1-*]_pwm |
229 | temp[1-*]_auto_point[1-*]_temp | |
230 | temp[1-*]_auto_point[1-*]_temp_hyst | |
231 | Define the PWM vs temperature curve. Number of trip points is | |
232 | chip-dependent. Use this for chips which associate trip points | |
233 | to temperature channels. | |
057bc350 | 234 | RW |
1da177e4 | 235 | |
f7290e24 JD |
236 | There is a third case where trip points are associated to both PWM output |
237 | channels and temperature channels: the PWM values are associated to PWM | |
238 | output channels while the temperature values are associated to temperature | |
239 | channels. In that case, the result is determined by the mapping between | |
240 | temperature inputs and PWM outputs. When several temperature inputs are | |
241 | mapped to a given PWM output, this leads to several candidate PWM values. | |
242 | The actual result is up to the chip, but in general the highest candidate | |
243 | value (fastest fan speed) wins. | |
244 | ||
1da177e4 LT |
245 | |
246 | **************** | |
247 | * Temperatures * | |
248 | **************** | |
249 | ||
057bc350 | 250 | temp[1-*]_type Sensor type selection. |
b26f9330 | 251 | Integers 1 to 6 |
057bc350 | 252 | RW |
1da177e4 LT |
253 | 1: PII/Celeron Diode |
254 | 2: 3904 transistor | |
255 | 3: thermal diode | |
b26f9330 | 256 | 4: thermistor |
61db011d RM |
257 | 5: AMD AMDSI |
258 | 6: Intel PECI | |
1da177e4 LT |
259 | Not all types are supported by all chips |
260 | ||
057bc350 | 261 | temp[1-*]_max Temperature max value. |
740e06a8 | 262 | Unit: millidegree Celsius (or millivolt, see below) |
057bc350 | 263 | RW |
1da177e4 | 264 | |
057bc350 | 265 | temp[1-*]_min Temperature min value. |
740e06a8 | 266 | Unit: millidegree Celsius |
057bc350 | 267 | RW |
1da177e4 | 268 | |
057bc350 | 269 | temp[1-*]_max_hyst |
1da177e4 | 270 | Temperature hysteresis value for max limit. |
740e06a8 | 271 | Unit: millidegree Celsius |
1da177e4 LT |
272 | Must be reported as an absolute temperature, NOT a delta |
273 | from the max value. | |
057bc350 | 274 | RW |
1da177e4 | 275 | |
057bc350 | 276 | temp[1-*]_input Temperature input value. |
740e06a8 | 277 | Unit: millidegree Celsius |
057bc350 | 278 | RO |
1da177e4 | 279 | |
057bc350 | 280 | temp[1-*]_crit Temperature critical value, typically greater than |
1da177e4 | 281 | corresponding temp_max values. |
740e06a8 | 282 | Unit: millidegree Celsius |
057bc350 | 283 | RW |
1da177e4 | 284 | |
057bc350 | 285 | temp[1-*]_crit_hyst |
1da177e4 | 286 | Temperature hysteresis value for critical limit. |
740e06a8 | 287 | Unit: millidegree Celsius |
1da177e4 LT |
288 | Must be reported as an absolute temperature, NOT a delta |
289 | from the critical value. | |
057bc350 | 290 | RW |
1da177e4 | 291 | |
176544dc | 292 | temp[1-*]_offset |
59ac8367 HR |
293 | Temperature offset which is added to the temperature reading |
294 | by the chip. | |
295 | Unit: millidegree Celsius | |
296 | Read/Write value. | |
297 | ||
176544dc JD |
298 | temp[1-*]_label Suggested temperature channel label. |
299 | Text string | |
300 | Should only be created if the driver has hints about what | |
301 | this temperature channel is being used for, and user-space | |
302 | doesn't. In all other cases, the label is provided by | |
303 | user-space. | |
304 | RO | |
1da177e4 | 305 | |
cd4e96c5 AP |
306 | temp[1-*]_lowest |
307 | Historical minimum temperature | |
308 | Unit: millidegree Celsius | |
309 | RO | |
310 | ||
311 | temp[1-*]_highest | |
312 | Historical maximum temperature | |
313 | Unit: millidegree Celsius | |
314 | RO | |
315 | ||
316 | temp[1-*]_reset_history | |
317 | Reset temp_lowest and temp_highest | |
318 | WO | |
319 | ||
320 | temp_reset_history | |
321 | Reset temp_lowest and temp_highest for all sensors | |
322 | WO | |
323 | ||
740e06a8 JD |
324 | Some chips measure temperature using external thermistors and an ADC, and |
325 | report the temperature measurement as a voltage. Converting this voltage | |
326 | back to a temperature (or the other way around for limits) requires | |
327 | mathematical functions not available in the kernel, so the conversion | |
328 | must occur in user space. For these chips, all temp* files described | |
329 | above should contain values expressed in millivolt instead of millidegree | |
330 | Celsius. In other words, such temperature channels are handled as voltage | |
331 | channels by the driver. | |
332 | ||
057bc350 RM |
333 | Also see the Alarms section for status flags associated with temperatures. |
334 | ||
1da177e4 LT |
335 | |
336 | ************ | |
337 | * Currents * | |
338 | ************ | |
339 | ||
340 | Note that no known chip provides current measurements as of writing, | |
341 | so this part is theoretical, so to say. | |
342 | ||
057bc350 | 343 | curr[1-*]_max Current max value |
1da177e4 | 344 | Unit: milliampere |
057bc350 | 345 | RW |
1da177e4 | 346 | |
057bc350 | 347 | curr[1-*]_min Current min value. |
1da177e4 | 348 | Unit: milliampere |
057bc350 | 349 | RW |
1da177e4 | 350 | |
057bc350 | 351 | curr[1-*]_input Current input value |
1da177e4 | 352 | Unit: milliampere |
057bc350 | 353 | RO |
1da177e4 | 354 | |
38fb56a2 DW |
355 | ********* |
356 | * Power * | |
357 | ********* | |
358 | ||
359 | power[1-*]_average Average power use | |
360 | Unit: microWatt | |
361 | RO | |
362 | ||
115a57c5 DW |
363 | power[1-*]_average_interval Power use averaging interval. A poll |
364 | notification is sent to this file if the | |
365 | hardware changes the averaging interval. | |
ddedc658 DW |
366 | Unit: milliseconds |
367 | RW | |
368 | ||
115a57c5 DW |
369 | power[1-*]_average_interval_max Maximum power use averaging interval |
370 | Unit: milliseconds | |
371 | RO | |
372 | ||
373 | power[1-*]_average_interval_min Minimum power use averaging interval | |
374 | Unit: milliseconds | |
375 | RO | |
376 | ||
38fb56a2 DW |
377 | power[1-*]_average_highest Historical average maximum power use |
378 | Unit: microWatt | |
379 | RO | |
380 | ||
381 | power[1-*]_average_lowest Historical average minimum power use | |
382 | Unit: microWatt | |
383 | RO | |
384 | ||
115a57c5 DW |
385 | power[1-*]_average_max A poll notification is sent to |
386 | power[1-*]_average when power use | |
387 | rises above this value. | |
388 | Unit: microWatt | |
389 | RW | |
390 | ||
391 | power[1-*]_average_min A poll notification is sent to | |
392 | power[1-*]_average when power use | |
393 | sinks below this value. | |
394 | Unit: microWatt | |
395 | RW | |
396 | ||
38fb56a2 DW |
397 | power[1-*]_input Instantaneous power use |
398 | Unit: microWatt | |
399 | RO | |
400 | ||
401 | power[1-*]_input_highest Historical maximum power use | |
402 | Unit: microWatt | |
403 | RO | |
404 | ||
405 | power[1-*]_input_lowest Historical minimum power use | |
406 | Unit: microWatt | |
407 | RO | |
408 | ||
409 | power[1-*]_reset_history Reset input_highest, input_lowest, | |
410 | average_highest and average_lowest. | |
411 | WO | |
1da177e4 | 412 | |
115a57c5 DW |
413 | power[1-*]_accuracy Accuracy of the power meter. |
414 | Unit: Percent | |
415 | RO | |
416 | ||
417 | power[1-*]_alarm 1 if the system is drawing more power than the | |
418 | cap allows; 0 otherwise. A poll notification is | |
419 | sent to this file when the power use exceeds the | |
420 | cap. This file only appears if the cap is known | |
421 | to be enforced by hardware. | |
422 | RO | |
423 | ||
424 | power[1-*]_cap If power use rises above this limit, the | |
425 | system should take action to reduce power use. | |
426 | A poll notification is sent to this file if the | |
427 | cap is changed by the hardware. The *_cap | |
428 | files only appear if the cap is known to be | |
429 | enforced by hardware. | |
430 | Unit: microWatt | |
431 | RW | |
432 | ||
433 | power[1-*]_cap_hyst Margin of hysteresis built around capping and | |
434 | notification. | |
435 | Unit: microWatt | |
436 | RW | |
437 | ||
438 | power[1-*]_cap_max Maximum cap that can be set. | |
439 | Unit: microWatt | |
440 | RO | |
441 | ||
442 | power[1-*]_cap_min Minimum cap that can be set. | |
443 | Unit: microWatt | |
444 | RO | |
445 | ||
ddedc658 DW |
446 | ********** |
447 | * Energy * | |
448 | ********** | |
449 | ||
450 | energy[1-*]_input Cumulative energy use | |
451 | Unit: microJoule | |
452 | RO | |
453 | ||
ec199209 | 454 | |
400b48ec JD |
455 | ********** |
456 | * Alarms * | |
457 | ********** | |
458 | ||
459 | Each channel or limit may have an associated alarm file, containing a | |
460 | boolean value. 1 means than an alarm condition exists, 0 means no alarm. | |
461 | ||
462 | Usually a given chip will either use channel-related alarms, or | |
463 | limit-related alarms, not both. The driver should just reflect the hardware | |
464 | implementation. | |
465 | ||
057bc350 RM |
466 | in[0-*]_alarm |
467 | fan[1-*]_alarm | |
468 | temp[1-*]_alarm | |
400b48ec | 469 | Channel alarm |
057bc350 RM |
470 | 0: no alarm |
471 | 1: alarm | |
472 | RO | |
400b48ec JD |
473 | |
474 | OR | |
475 | ||
057bc350 RM |
476 | in[0-*]_min_alarm |
477 | in[0-*]_max_alarm | |
478 | fan[1-*]_min_alarm | |
d54d4624 | 479 | fan[1-*]_max_alarm |
057bc350 RM |
480 | temp[1-*]_min_alarm |
481 | temp[1-*]_max_alarm | |
482 | temp[1-*]_crit_alarm | |
400b48ec | 483 | Limit alarm |
057bc350 RM |
484 | 0: no alarm |
485 | 1: alarm | |
486 | RO | |
400b48ec JD |
487 | |
488 | Each input channel may have an associated fault file. This can be used | |
489 | to notify open diodes, unconnected fans etc. where the hardware | |
490 | supports it. When this boolean has value 1, the measurement for that | |
491 | channel should not be trusted. | |
492 | ||
7817a39e JD |
493 | in[0-*]_fault |
494 | fan[1-*]_fault | |
495 | temp[1-*]_fault | |
400b48ec | 496 | Input fault condition |
057bc350 RM |
497 | 0: no fault occured |
498 | 1: fault condition | |
499 | RO | |
400b48ec JD |
500 | |
501 | Some chips also offer the possibility to get beeped when an alarm occurs: | |
502 | ||
503 | beep_enable Master beep enable | |
057bc350 RM |
504 | 0: no beeps |
505 | 1: beeps | |
506 | RW | |
400b48ec | 507 | |
057bc350 RM |
508 | in[0-*]_beep |
509 | fan[1-*]_beep | |
510 | temp[1-*]_beep | |
400b48ec | 511 | Channel beep |
057bc350 RM |
512 | 0: disable |
513 | 1: enable | |
514 | RW | |
400b48ec JD |
515 | |
516 | In theory, a chip could provide per-limit beep masking, but no such chip | |
517 | was seen so far. | |
518 | ||
519 | Old drivers provided a different, non-standard interface to alarms and | |
520 | beeps. These interface files are deprecated, but will be kept around | |
521 | for compatibility reasons: | |
1da177e4 LT |
522 | |
523 | alarms Alarm bitmask. | |
057bc350 | 524 | RO |
1da177e4 LT |
525 | Integer representation of one to four bytes. |
526 | A '1' bit means an alarm. | |
527 | Chips should be programmed for 'comparator' mode so that | |
528 | the alarm will 'come back' after you read the register | |
529 | if it is still valid. | |
530 | Generally a direct representation of a chip's internal | |
531 | alarm registers; there is no standard for the position | |
400b48ec JD |
532 | of individual bits. For this reason, the use of this |
533 | interface file for new drivers is discouraged. Use | |
534 | individual *_alarm and *_fault files instead. | |
1da177e4 LT |
535 | Bits are defined in kernel/include/sensors.h. |
536 | ||
1da177e4 | 537 | beep_mask Bitmask for beep. |
400b48ec JD |
538 | Same format as 'alarms' with the same bit locations, |
539 | use discouraged for the same reason. Use individual | |
540 | *_beep files instead. | |
057bc350 | 541 | RW |
2ed42633 HG |
542 | |
543 | ||
ec199209 JD |
544 | *********************** |
545 | * Intrusion detection * | |
546 | *********************** | |
547 | ||
548 | intrusion[0-*]_alarm | |
549 | Chassis intrusion detection | |
550 | 0: OK | |
551 | 1: intrusion detected | |
552 | RW | |
553 | Contrary to regular alarm flags which clear themselves | |
554 | automatically when read, this one sticks until cleared by | |
555 | the user. This is done by writing 0 to the file. Writing | |
556 | other values is unsupported. | |
557 | ||
558 | intrusion[0-*]_beep | |
559 | Chassis intrusion beep | |
560 | 0: disable | |
561 | 1: enable | |
562 | RW | |
563 | ||
564 | ||
2ed42633 HG |
565 | sysfs attribute writes interpretation |
566 | ------------------------------------- | |
567 | ||
568 | hwmon sysfs attributes always contain numbers, so the first thing to do is to | |
569 | convert the input to a number, there are 2 ways todo this depending whether | |
570 | the number can be negative or not: | |
571 | unsigned long u = simple_strtoul(buf, NULL, 10); | |
572 | long s = simple_strtol(buf, NULL, 10); | |
573 | ||
574 | With buf being the buffer with the user input being passed by the kernel. | |
575 | Notice that we do not use the second argument of strto[u]l, and thus cannot | |
576 | tell when 0 is returned, if this was really 0 or is caused by invalid input. | |
577 | This is done deliberately as checking this everywhere would add a lot of | |
578 | code to the kernel. | |
579 | ||
580 | Notice that it is important to always store the converted value in an | |
581 | unsigned long or long, so that no wrap around can happen before any further | |
582 | checking. | |
583 | ||
584 | After the input string is converted to an (unsigned) long, the value should be | |
585 | checked if its acceptable. Be careful with further conversions on the value | |
586 | before checking it for validity, as these conversions could still cause a wrap | |
587 | around before the check. For example do not multiply the result, and only | |
588 | add/subtract if it has been divided before the add/subtract. | |
589 | ||
590 | What to do if a value is found to be invalid, depends on the type of the | |
591 | sysfs attribute that is being set. If it is a continuous setting like a | |
592 | tempX_max or inX_max attribute, then the value should be clamped to its | |
593 | limits using SENSORS_LIMIT(value, min_limit, max_limit). If it is not | |
594 | continuous like for example a tempX_type, then when an invalid value is | |
595 | written, -EINVAL should be returned. | |
596 | ||
597 | Example1, temp1_max, register is a signed 8 bit value (-128 - 127 degrees): | |
5fbea518 JD |
598 | |
599 | long v = simple_strtol(buf, NULL, 10) / 1000; | |
600 | v = SENSORS_LIMIT(v, -128, 127); | |
601 | /* write v to register */ | |
2ed42633 HG |
602 | |
603 | Example2, fan divider setting, valid values 2, 4 and 8: | |
5fbea518 JD |
604 | |
605 | unsigned long v = simple_strtoul(buf, NULL, 10); | |
606 | ||
607 | switch (v) { | |
608 | case 2: v = 1; break; | |
609 | case 4: v = 2; break; | |
610 | case 8: v = 3; break; | |
611 | default: | |
612 | return -EINVAL; | |
613 | } | |
614 | /* write v to register */ |