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203d3d4a | 1 | Generic Thermal Sysfs driver How To |
38bb0849 | 2 | =================================== |
203d3d4a ZR |
3 | |
4 | Written by Sujith Thomas <sujith.thomas@intel.com>, Zhang Rui <rui.zhang@intel.com> | |
5 | ||
6 | Updated: 2 January 2008 | |
7 | ||
8 | Copyright (c) 2008 Intel Corporation | |
9 | ||
10 | ||
11 | 0. Introduction | |
12 | ||
38bb0849 FP |
13 | The generic thermal sysfs provides a set of interfaces for thermal zone |
14 | devices (sensors) and thermal cooling devices (fan, processor...) to register | |
15 | with the thermal management solution and to be a part of it. | |
203d3d4a | 16 | |
38bb0849 FP |
17 | This how-to focuses on enabling new thermal zone and cooling devices to |
18 | participate in thermal management. | |
19 | This solution is platform independent and any type of thermal zone devices | |
20 | and cooling devices should be able to make use of the infrastructure. | |
203d3d4a | 21 | |
38bb0849 FP |
22 | The main task of the thermal sysfs driver is to expose thermal zone attributes |
23 | as well as cooling device attributes to the user space. | |
24 | An intelligent thermal management application can make decisions based on | |
25 | inputs from thermal zone attributes (the current temperature and trip point | |
26 | temperature) and throttle appropriate devices. | |
203d3d4a ZR |
27 | |
28 | [0-*] denotes any positive number starting from 0 | |
29 | [1-*] denotes any positive number starting from 1 | |
30 | ||
31 | 1. thermal sysfs driver interface functions | |
32 | ||
33 | 1.1 thermal zone device interface | |
514e6d20 | 34 | 1.1.1 struct thermal_zone_device *thermal_zone_device_register(char *type, |
c56f5c03 | 35 | int trips, int mask, void *devdata, |
514e6d20 ZR |
36 | struct thermal_zone_device_ops *ops, |
37 | const struct thermal_zone_params *tzp, | |
38 | int passive_delay, int polling_delay)) | |
38bb0849 FP |
39 | |
40 | This interface function adds a new thermal zone device (sensor) to | |
41 | /sys/class/thermal folder as thermal_zone[0-*]. It tries to bind all the | |
42 | thermal cooling devices registered at the same time. | |
43 | ||
514e6d20 | 44 | type: the thermal zone type. |
38bb0849 | 45 | trips: the total number of trip points this thermal zone supports. |
c56f5c03 | 46 | mask: Bit string: If 'n'th bit is set, then trip point 'n' is writeable. |
38bb0849 FP |
47 | devdata: device private data |
48 | ops: thermal zone device call-backs. | |
49 | .bind: bind the thermal zone device with a thermal cooling device. | |
50 | .unbind: unbind the thermal zone device with a thermal cooling device. | |
51 | .get_temp: get the current temperature of the thermal zone. | |
8eaa8d6c ZR |
52 | .get_mode: get the current mode (enabled/disabled) of the thermal zone. |
53 | - "enabled" means the kernel thermal management is enabled. | |
54 | - "disabled" will prevent kernel thermal driver action upon trip points | |
38bb0849 | 55 | so that user applications can take charge of thermal management. |
8eaa8d6c | 56 | .set_mode: set the mode (enabled/disabled) of the thermal zone. |
38bb0849 FP |
57 | .get_trip_type: get the type of certain trip point. |
58 | .get_trip_temp: get the temperature above which the certain trip point | |
59 | will be fired. | |
e6e238c3 ADK |
60 | .set_emul_temp: set the emulation temperature which helps in debugging |
61 | different threshold temperature points. | |
514e6d20 ZR |
62 | tzp: thermal zone platform parameters. |
63 | passive_delay: number of milliseconds to wait between polls when | |
64 | performing passive cooling. | |
65 | polling_delay: number of milliseconds to wait between polls when checking | |
66 | whether trip points have been crossed (0 for interrupt driven systems). | |
67 | ||
203d3d4a ZR |
68 | |
69 | 1.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz) | |
70 | ||
38bb0849 FP |
71 | This interface function removes the thermal zone device. |
72 | It deletes the corresponding entry form /sys/class/thermal folder and | |
73 | unbind all the thermal cooling devices it uses. | |
203d3d4a ZR |
74 | |
75 | 1.2 thermal cooling device interface | |
76 | 1.2.1 struct thermal_cooling_device *thermal_cooling_device_register(char *name, | |
38bb0849 FP |
77 | void *devdata, struct thermal_cooling_device_ops *) |
78 | ||
79 | This interface function adds a new thermal cooling device (fan/processor/...) | |
80 | to /sys/class/thermal/ folder as cooling_device[0-*]. It tries to bind itself | |
81 | to all the thermal zone devices register at the same time. | |
82 | name: the cooling device name. | |
83 | devdata: device private data. | |
84 | ops: thermal cooling devices call-backs. | |
85 | .get_max_state: get the Maximum throttle state of the cooling device. | |
86 | .get_cur_state: get the Current throttle state of the cooling device. | |
87 | .set_cur_state: set the Current throttle state of the cooling device. | |
203d3d4a ZR |
88 | |
89 | 1.2.2 void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev) | |
90 | ||
38bb0849 FP |
91 | This interface function remove the thermal cooling device. |
92 | It deletes the corresponding entry form /sys/class/thermal folder and | |
93 | unbind itself from all the thermal zone devices using it. | |
203d3d4a ZR |
94 | |
95 | 1.3 interface for binding a thermal zone device with a thermal cooling device | |
96 | 1.3.1 int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz, | |
9d99842f | 97 | int trip, struct thermal_cooling_device *cdev, |
6cd9e9f6 | 98 | unsigned long upper, unsigned long lower, unsigned int weight); |
203d3d4a | 99 | |
38bb0849 FP |
100 | This interface function bind a thermal cooling device to the certain trip |
101 | point of a thermal zone device. | |
102 | This function is usually called in the thermal zone device .bind callback. | |
103 | tz: the thermal zone device | |
104 | cdev: thermal cooling device | |
105 | trip: indicates which trip point the cooling devices is associated with | |
106 | in this thermal zone. | |
9d99842f ZR |
107 | upper:the Maximum cooling state for this trip point. |
108 | THERMAL_NO_LIMIT means no upper limit, | |
109 | and the cooling device can be in max_state. | |
110 | lower:the Minimum cooling state can be used for this trip point. | |
111 | THERMAL_NO_LIMIT means no lower limit, | |
112 | and the cooling device can be in cooling state 0. | |
6cd9e9f6 KS |
113 | weight: the influence of this cooling device in this thermal |
114 | zone. See 1.4.1 below for more information. | |
203d3d4a ZR |
115 | |
116 | 1.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz, | |
38bb0849 | 117 | int trip, struct thermal_cooling_device *cdev); |
203d3d4a | 118 | |
38bb0849 FP |
119 | This interface function unbind a thermal cooling device from the certain |
120 | trip point of a thermal zone device. This function is usually called in | |
121 | the thermal zone device .unbind callback. | |
122 | tz: the thermal zone device | |
123 | cdev: thermal cooling device | |
124 | trip: indicates which trip point the cooling devices is associated with | |
125 | in this thermal zone. | |
203d3d4a | 126 | |
6ea083b1 D |
127 | 1.4 Thermal Zone Parameters |
128 | 1.4.1 struct thermal_bind_params | |
129 | This structure defines the following parameters that are used to bind | |
130 | a zone with a cooling device for a particular trip point. | |
131 | .cdev: The cooling device pointer | |
bcdcbbc7 JM |
132 | .weight: The 'influence' of a particular cooling device on this |
133 | zone. This is relative to the rest of the cooling | |
134 | devices. For example, if all cooling devices have a | |
135 | weight of 1, then they all contribute the same. You can | |
136 | use percentages if you want, but it's not mandatory. A | |
137 | weight of 0 means that this cooling device doesn't | |
138 | contribute to the cooling of this zone unless all cooling | |
139 | devices have a weight of 0. If all weights are 0, then | |
140 | they all contribute the same. | |
6ea083b1 D |
141 | .trip_mask:This is a bit mask that gives the binding relation between |
142 | this thermal zone and cdev, for a particular trip point. | |
143 | If nth bit is set, then the cdev and thermal zone are bound | |
144 | for trip point n. | |
a8892d83 EV |
145 | .limits: This is an array of cooling state limits. Must have exactly |
146 | 2 * thermal_zone.number_of_trip_points. It is an array consisting | |
147 | of tuples <lower-state upper-state> of state limits. Each trip | |
148 | will be associated with one state limit tuple when binding. | |
149 | A NULL pointer means <THERMAL_NO_LIMITS THERMAL_NO_LIMITS> | |
150 | on all trips. These limits are used when binding a cdev to a | |
151 | trip point. | |
6ea083b1 D |
152 | .match: This call back returns success(0) if the 'tz and cdev' need to |
153 | be bound, as per platform data. | |
154 | 1.4.2 struct thermal_zone_params | |
155 | This structure defines the platform level parameters for a thermal zone. | |
156 | This data, for each thermal zone should come from the platform layer. | |
157 | This is an optional feature where some platforms can choose not to | |
158 | provide this data. | |
159 | .governor_name: Name of the thermal governor used for this zone | |
ccba4ffd EV |
160 | .no_hwmon: a boolean to indicate if the thermal to hwmon sysfs interface |
161 | is required. when no_hwmon == false, a hwmon sysfs interface | |
162 | will be created. when no_hwmon == true, nothing will be done. | |
163 | In case the thermal_zone_params is NULL, the hwmon interface | |
164 | will be created (for backward compatibility). | |
6ea083b1 D |
165 | .num_tbps: Number of thermal_bind_params entries for this zone |
166 | .tbp: thermal_bind_params entries | |
167 | ||
203d3d4a ZR |
168 | 2. sysfs attributes structure |
169 | ||
170 | RO read only value | |
171 | RW read/write value | |
172 | ||
e9ae7107 ZR |
173 | Thermal sysfs attributes will be represented under /sys/class/thermal. |
174 | Hwmon sysfs I/F extension is also available under /sys/class/hwmon | |
175 | if hwmon is compiled in or built as a module. | |
203d3d4a ZR |
176 | |
177 | Thermal zone device sys I/F, created once it's registered: | |
e9ae7107 | 178 | /sys/class/thermal/thermal_zone[0-*]: |
38bb0849 FP |
179 | |---type: Type of the thermal zone |
180 | |---temp: Current temperature | |
181 | |---mode: Working mode of the thermal zone | |
6ea083b1 | 182 | |---policy: Thermal governor used for this zone |
25a0a5ce | 183 | |---available_policies: Available thermal governors for this zone |
38bb0849 FP |
184 | |---trip_point_[0-*]_temp: Trip point temperature |
185 | |---trip_point_[0-*]_type: Trip point type | |
27365a6c | 186 | |---trip_point_[0-*]_hyst: Hysteresis value for this trip point |
e6e238c3 | 187 | |---emul_temp: Emulated temperature set node |
9f38271c JM |
188 | |---sustainable_power: Sustainable dissipatable power |
189 | |---k_po: Proportional term during temperature overshoot | |
190 | |---k_pu: Proportional term during temperature undershoot | |
191 | |---k_i: PID's integral term in the power allocator gov | |
192 | |---k_d: PID's derivative term in the power allocator | |
193 | |---integral_cutoff: Offset above which errors are accumulated | |
9d0be7f4 EV |
194 | |---slope: Slope constant applied as linear extrapolation |
195 | |---offset: Offset constant applied as linear extrapolation | |
203d3d4a ZR |
196 | |
197 | Thermal cooling device sys I/F, created once it's registered: | |
e9ae7107 | 198 | /sys/class/thermal/cooling_device[0-*]: |
38bb0849 FP |
199 | |---type: Type of the cooling device(processor/fan/...) |
200 | |---max_state: Maximum cooling state of the cooling device | |
201 | |---cur_state: Current cooling state of the cooling device | |
203d3d4a ZR |
202 | |
203 | ||
38bb0849 FP |
204 | Then next two dynamic attributes are created/removed in pairs. They represent |
205 | the relationship between a thermal zone and its associated cooling device. | |
206 | They are created/removed for each successful execution of | |
207 | thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device. | |
203d3d4a | 208 | |
38bb0849 FP |
209 | /sys/class/thermal/thermal_zone[0-*]: |
210 | |---cdev[0-*]: [0-*]th cooling device in current thermal zone | |
211 | |---cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with | |
db916513 JM |
212 | |---cdev[0-*]_weight: Influence of the cooling device in |
213 | this thermal zone | |
203d3d4a | 214 | |
e9ae7107 | 215 | Besides the thermal zone device sysfs I/F and cooling device sysfs I/F, |
38bb0849 FP |
216 | the generic thermal driver also creates a hwmon sysfs I/F for each _type_ |
217 | of thermal zone device. E.g. the generic thermal driver registers one hwmon | |
218 | class device and build the associated hwmon sysfs I/F for all the registered | |
219 | ACPI thermal zones. | |
220 | ||
e9ae7107 | 221 | /sys/class/hwmon/hwmon[0-*]: |
38bb0849 FP |
222 | |---name: The type of the thermal zone devices |
223 | |---temp[1-*]_input: The current temperature of thermal zone [1-*] | |
224 | |---temp[1-*]_critical: The critical trip point of thermal zone [1-*] | |
225 | ||
e9ae7107 | 226 | Please read Documentation/hwmon/sysfs-interface for additional information. |
203d3d4a ZR |
227 | |
228 | *************************** | |
229 | * Thermal zone attributes * | |
230 | *************************** | |
231 | ||
38bb0849 FP |
232 | type |
233 | Strings which represent the thermal zone type. | |
234 | This is given by thermal zone driver as part of registration. | |
235 | E.g: "acpitz" indicates it's an ACPI thermal device. | |
236 | In order to keep it consistent with hwmon sys attribute; this should | |
237 | be a short, lowercase string, not containing spaces nor dashes. | |
238 | RO, Required | |
239 | ||
240 | temp | |
241 | Current temperature as reported by thermal zone (sensor). | |
242 | Unit: millidegree Celsius | |
243 | RO, Required | |
244 | ||
245 | mode | |
8eaa8d6c | 246 | One of the predefined values in [enabled, disabled]. |
38bb0849 FP |
247 | This file gives information about the algorithm that is currently |
248 | managing the thermal zone. It can be either default kernel based | |
249 | algorithm or user space application. | |
8eaa8d6c ZR |
250 | enabled = enable Kernel Thermal management. |
251 | disabled = Preventing kernel thermal zone driver actions upon | |
252 | trip points so that user application can take full | |
253 | charge of the thermal management. | |
38bb0849 FP |
254 | RW, Optional |
255 | ||
6ea083b1 D |
256 | policy |
257 | One of the various thermal governors used for a particular zone. | |
258 | RW, Required | |
259 | ||
25a0a5ce NW |
260 | available_policies |
261 | Available thermal governors which can be used for a particular zone. | |
262 | RO, Required | |
263 | ||
38bb0849 FP |
264 | trip_point_[0-*]_temp |
265 | The temperature above which trip point will be fired. | |
266 | Unit: millidegree Celsius | |
267 | RO, Optional | |
268 | ||
269 | trip_point_[0-*]_type | |
270 | Strings which indicate the type of the trip point. | |
271 | E.g. it can be one of critical, hot, passive, active[0-*] for ACPI | |
272 | thermal zone. | |
273 | RO, Optional | |
274 | ||
27365a6c D |
275 | trip_point_[0-*]_hyst |
276 | The hysteresis value for a trip point, represented as an integer | |
277 | Unit: Celsius | |
278 | RW, Optional | |
279 | ||
38bb0849 FP |
280 | cdev[0-*] |
281 | Sysfs link to the thermal cooling device node where the sys I/F | |
282 | for cooling device throttling control represents. | |
283 | RO, Optional | |
284 | ||
285 | cdev[0-*]_trip_point | |
286 | The trip point with which cdev[0-*] is associated in this thermal | |
287 | zone; -1 means the cooling device is not associated with any trip | |
288 | point. | |
289 | RO, Optional | |
29226ed3 | 290 | |
db916513 JM |
291 | cdev[0-*]_weight |
292 | The influence of cdev[0-*] in this thermal zone. This value | |
293 | is relative to the rest of cooling devices in the thermal | |
294 | zone. For example, if a cooling device has a weight double | |
295 | than that of other, it's twice as effective in cooling the | |
296 | thermal zone. | |
297 | RW, Optional | |
298 | ||
29226ed3 FP |
299 | passive |
300 | Attribute is only present for zones in which the passive cooling | |
301 | policy is not supported by native thermal driver. Default is zero | |
302 | and can be set to a temperature (in millidegrees) to enable a | |
303 | passive trip point for the zone. Activation is done by polling with | |
304 | an interval of 1 second. | |
305 | Unit: millidegrees Celsius | |
3d8e3ad8 | 306 | Valid values: 0 (disabled) or greater than 1000 |
29226ed3 | 307 | RW, Optional |
38bb0849 | 308 | |
e6e238c3 ADK |
309 | emul_temp |
310 | Interface to set the emulated temperature method in thermal zone | |
311 | (sensor). After setting this temperature, the thermal zone may pass | |
312 | this temperature to platform emulation function if registered or | |
313 | cache it locally. This is useful in debugging different temperature | |
314 | threshold and its associated cooling action. This is write only node | |
315 | and writing 0 on this node should disable emulation. | |
316 | Unit: millidegree Celsius | |
317 | WO, Optional | |
318 | ||
8837295a EV |
319 | WARNING: Be careful while enabling this option on production systems, |
320 | because userland can easily disable the thermal policy by simply | |
321 | flooding this sysfs node with low temperature values. | |
322 | ||
9f38271c JM |
323 | sustainable_power |
324 | An estimate of the sustained power that can be dissipated by | |
325 | the thermal zone. Used by the power allocator governor. For | |
326 | more information see Documentation/thermal/power_allocator.txt | |
327 | Unit: milliwatts | |
328 | RW, Optional | |
329 | ||
330 | k_po | |
331 | The proportional term of the power allocator governor's PID | |
332 | controller during temperature overshoot. Temperature overshoot | |
333 | is when the current temperature is above the "desired | |
334 | temperature" trip point. For more information see | |
335 | Documentation/thermal/power_allocator.txt | |
336 | RW, Optional | |
337 | ||
338 | k_pu | |
339 | The proportional term of the power allocator governor's PID | |
340 | controller during temperature undershoot. Temperature undershoot | |
341 | is when the current temperature is below the "desired | |
342 | temperature" trip point. For more information see | |
343 | Documentation/thermal/power_allocator.txt | |
344 | RW, Optional | |
345 | ||
346 | k_i | |
347 | The integral term of the power allocator governor's PID | |
348 | controller. This term allows the PID controller to compensate | |
349 | for long term drift. For more information see | |
350 | Documentation/thermal/power_allocator.txt | |
351 | RW, Optional | |
352 | ||
353 | k_d | |
354 | The derivative term of the power allocator governor's PID | |
355 | controller. For more information see | |
356 | Documentation/thermal/power_allocator.txt | |
357 | RW, Optional | |
358 | ||
359 | integral_cutoff | |
360 | Temperature offset from the desired temperature trip point | |
361 | above which the integral term of the power allocator | |
362 | governor's PID controller starts accumulating errors. For | |
363 | example, if integral_cutoff is 0, then the integral term only | |
364 | accumulates error when temperature is above the desired | |
365 | temperature trip point. For more information see | |
366 | Documentation/thermal/power_allocator.txt | |
ec3fc58b | 367 | Unit: millidegree Celsius |
9f38271c JM |
368 | RW, Optional |
369 | ||
9d0be7f4 EV |
370 | slope |
371 | The slope constant used in a linear extrapolation model | |
372 | to determine a hotspot temperature based off the sensor's | |
373 | raw readings. It is up to the device driver to determine | |
374 | the usage of these values. | |
375 | RW, Optional | |
376 | ||
377 | offset | |
378 | The offset constant used in a linear extrapolation model | |
379 | to determine a hotspot temperature based off the sensor's | |
380 | raw readings. It is up to the device driver to determine | |
381 | the usage of these values. | |
382 | RW, Optional | |
383 | ||
38bb0849 FP |
384 | ***************************** |
385 | * Cooling device attributes * | |
386 | ***************************** | |
387 | ||
388 | type | |
389 | String which represents the type of device, e.g: | |
390 | - for generic ACPI: should be "Fan", "Processor" or "LCD" | |
391 | - for memory controller device on intel_menlow platform: | |
392 | should be "Memory controller". | |
393 | RO, Required | |
394 | ||
395 | max_state | |
396 | The maximum permissible cooling state of this cooling device. | |
397 | RO, Required | |
398 | ||
399 | cur_state | |
400 | The current cooling state of this cooling device. | |
401 | The value can any integer numbers between 0 and max_state: | |
402 | - cur_state == 0 means no cooling | |
403 | - cur_state == max_state means the maximum cooling. | |
404 | RW, Required | |
203d3d4a ZR |
405 | |
406 | 3. A simple implementation | |
407 | ||
38bb0849 FP |
408 | ACPI thermal zone may support multiple trip points like critical, hot, |
409 | passive, active. If an ACPI thermal zone supports critical, passive, | |
410 | active[0] and active[1] at the same time, it may register itself as a | |
411 | thermal_zone_device (thermal_zone1) with 4 trip points in all. | |
412 | It has one processor and one fan, which are both registered as | |
db916513 JM |
413 | thermal_cooling_device. Both are considered to have the same |
414 | effectiveness in cooling the thermal zone. | |
38bb0849 FP |
415 | |
416 | If the processor is listed in _PSL method, and the fan is listed in _AL0 | |
417 | method, the sys I/F structure will be built like this: | |
203d3d4a ZR |
418 | |
419 | /sys/class/thermal: | |
420 | ||
421 | |thermal_zone1: | |
38bb0849 FP |
422 | |---type: acpitz |
423 | |---temp: 37000 | |
8eaa8d6c | 424 | |---mode: enabled |
6ea083b1 | 425 | |---policy: step_wise |
25a0a5ce | 426 | |---available_policies: step_wise fair_share |
38bb0849 FP |
427 | |---trip_point_0_temp: 100000 |
428 | |---trip_point_0_type: critical | |
429 | |---trip_point_1_temp: 80000 | |
430 | |---trip_point_1_type: passive | |
431 | |---trip_point_2_temp: 70000 | |
432 | |---trip_point_2_type: active0 | |
433 | |---trip_point_3_temp: 60000 | |
434 | |---trip_point_3_type: active1 | |
435 | |---cdev0: --->/sys/class/thermal/cooling_device0 | |
436 | |---cdev0_trip_point: 1 /* cdev0 can be used for passive */ | |
db916513 | 437 | |---cdev0_weight: 1024 |
38bb0849 FP |
438 | |---cdev1: --->/sys/class/thermal/cooling_device3 |
439 | |---cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/ | |
db916513 | 440 | |---cdev1_weight: 1024 |
203d3d4a ZR |
441 | |
442 | |cooling_device0: | |
38bb0849 FP |
443 | |---type: Processor |
444 | |---max_state: 8 | |
445 | |---cur_state: 0 | |
203d3d4a ZR |
446 | |
447 | |cooling_device3: | |
38bb0849 FP |
448 | |---type: Fan |
449 | |---max_state: 2 | |
450 | |---cur_state: 0 | |
e9ae7107 ZR |
451 | |
452 | /sys/class/hwmon: | |
453 | ||
454 | |hwmon0: | |
38bb0849 FP |
455 | |---name: acpitz |
456 | |---temp1_input: 37000 | |
457 | |---temp1_crit: 100000 | |
4cb18728 D |
458 | |
459 | 4. Event Notification | |
460 | ||
461 | The framework includes a simple notification mechanism, in the form of a | |
462 | netlink event. Netlink socket initialization is done during the _init_ | |
463 | of the framework. Drivers which intend to use the notification mechanism | |
2d58d7ea | 464 | just need to call thermal_generate_netlink_event() with two arguments viz |
8ab3e6a0 EV |
465 | (originator, event). The originator is a pointer to struct thermal_zone_device |
466 | from where the event has been originated. An integer which represents the | |
467 | thermal zone device will be used in the message to identify the zone. The | |
4cb18728 D |
468 | event will be one of:{THERMAL_AUX0, THERMAL_AUX1, THERMAL_CRITICAL, |
469 | THERMAL_DEV_FAULT}. Notification can be sent when the current temperature | |
470 | crosses any of the configured thresholds. | |
6ea083b1 D |
471 | |
472 | 5. Export Symbol APIs: | |
473 | ||
474 | 5.1: get_tz_trend: | |
475 | This function returns the trend of a thermal zone, i.e the rate of change | |
476 | of temperature of the thermal zone. Ideally, the thermal sensor drivers | |
477 | are supposed to implement the callback. If they don't, the thermal | |
478 | framework calculated the trend by comparing the previous and the current | |
479 | temperature values. | |
480 | ||
481 | 5.2:get_thermal_instance: | |
482 | This function returns the thermal_instance corresponding to a given | |
483 | {thermal_zone, cooling_device, trip_point} combination. Returns NULL | |
484 | if such an instance does not exist. | |
485 | ||
7b73c993 | 486 | 5.3:thermal_notify_framework: |
6ea083b1 D |
487 | This function handles the trip events from sensor drivers. It starts |
488 | throttling the cooling devices according to the policy configured. | |
489 | For CRITICAL and HOT trip points, this notifies the respective drivers, | |
490 | and does actual throttling for other trip points i.e ACTIVE and PASSIVE. | |
491 | The throttling policy is based on the configured platform data; if no | |
492 | platform data is provided, this uses the step_wise throttling policy. | |
493 | ||
494 | 5.4:thermal_cdev_update: | |
495 | This function serves as an arbitrator to set the state of a cooling | |
496 | device. It sets the cooling device to the deepest cooling state if | |
497 | possible. |