diff options
Diffstat (limited to 'Documentation')
-rw-r--r-- | Documentation/thermal/sysfs-api.txt | 246 |
1 files changed, 246 insertions, 0 deletions
diff --git a/Documentation/thermal/sysfs-api.txt b/Documentation/thermal/sysfs-api.txt new file mode 100644 index 000000000000..5776e090359d --- /dev/null +++ b/Documentation/thermal/sysfs-api.txt | |||
@@ -0,0 +1,246 @@ | |||
1 | Generic Thermal Sysfs driver How To | ||
2 | ========================= | ||
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 | |||
13 | The generic thermal sysfs provides a set of interfaces for thermal zone devices (sensors) | ||
14 | and thermal cooling devices (fan, processor...) to register with the thermal management | ||
15 | solution and to be a part of it. | ||
16 | |||
17 | This how-to focusses on enabling new thermal zone and cooling devices to participate | ||
18 | in thermal management. | ||
19 | This solution is platform independent and any type of thermal zone devices and | ||
20 | cooling devices should be able to make use of the infrastructure. | ||
21 | |||
22 | The main task of the thermal sysfs driver is to expose thermal zone attributes as well | ||
23 | as cooling device attributes to the user space. | ||
24 | An intelligent thermal management application can make decisions based on inputs | ||
25 | from thermal zone attributes (the current temperature and trip point temperature) | ||
26 | and throttle appropriate devices. | ||
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 | ||
34 | 1.1.1 struct thermal_zone_device *thermal_zone_device_register(char *name, int trips, | ||
35 | void *devdata, struct thermal_zone_device_ops *ops) | ||
36 | |||
37 | This interface function adds a new thermal zone device (sensor) to | ||
38 | /sys/class/thermal folder as thermal_zone[0-*]. | ||
39 | It tries to bind all the thermal cooling devices registered at the same time. | ||
40 | |||
41 | name: the thermal zone name. | ||
42 | trips: the total number of trip points this thermal zone supports. | ||
43 | devdata: device private data | ||
44 | ops: thermal zone device callbacks. | ||
45 | .bind: bind the thermal zone device with a thermal cooling device. | ||
46 | .unbind: unbing the thermal zone device with a thermal cooling device. | ||
47 | .get_temp: get the current temperature of the thermal zone. | ||
48 | .get_mode: get the current mode (user/kernel) of the thermal zone. | ||
49 | "kernel" means thermal management is done in kernel. | ||
50 | "user" will prevent kernel thermal driver actions upon trip points | ||
51 | so that user applications can take charge of thermal management. | ||
52 | .set_mode: set the mode (user/kernel) of the thermal zone. | ||
53 | .get_trip_type: get the type of certain trip point. | ||
54 | .get_trip_temp: get the temperature above which the certain trip point | ||
55 | will be fired. | ||
56 | |||
57 | 1.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz) | ||
58 | |||
59 | This interface function removes the thermal zone device. | ||
60 | It deletes the corresponding entry form /sys/class/thermal folder and unbind all | ||
61 | the thermal cooling devices it uses. | ||
62 | |||
63 | 1.2 thermal cooling device interface | ||
64 | 1.2.1 struct thermal_cooling_device *thermal_cooling_device_register(char *name, | ||
65 | void *devdata, struct thermal_cooling_device_ops *) | ||
66 | |||
67 | This interface function adds a new thermal cooling device (fan/processor/...) to | ||
68 | /sys/class/thermal/ folder as cooling_device[0-*]. | ||
69 | It tries to bind itself to all the thermal zone devices register at the same time. | ||
70 | name: the cooling device name. | ||
71 | devdata: device private data. | ||
72 | ops: thermal cooling devices callbacks. | ||
73 | .get_max_state: get the Maximum throttle state of the cooling device. | ||
74 | .get_cur_state: get the Current throttle state of the cooling device. | ||
75 | .set_cur_state: set the Current throttle state of the cooling device. | ||
76 | |||
77 | 1.2.2 void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev) | ||
78 | |||
79 | This interface function remove the thermal cooling device. | ||
80 | It deletes the corresponding entry form /sys/class/thermal folder and unbind | ||
81 | itself from all the thermal zone devices using it. | ||
82 | |||
83 | 1.3 interface for binding a thermal zone device with a thermal cooling device | ||
84 | 1.3.1 int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz, | ||
85 | int trip, struct thermal_cooling_device *cdev); | ||
86 | |||
87 | This interface function bind a thermal cooling device to the certain trip point | ||
88 | of a thermal zone device. | ||
89 | This function is usually called in the thermal zone device .bind callback. | ||
90 | tz: the thermal zone device | ||
91 | cdev: thermal cooling device | ||
92 | trip: indicates which trip point the cooling devices is associated with | ||
93 | in this thermal zone. | ||
94 | |||
95 | 1.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz, | ||
96 | int trip, struct thermal_cooling_device *cdev); | ||
97 | |||
98 | This interface function unbind a thermal cooling device from the certain trip point | ||
99 | of a thermal zone device. | ||
100 | This function is usually called in the thermal zone device .unbind callback. | ||
101 | tz: the thermal zone device | ||
102 | cdev: thermal cooling device | ||
103 | trip: indicates which trip point the cooling devices is associated with | ||
104 | in this thermal zone. | ||
105 | |||
106 | 2. sysfs attributes structure | ||
107 | |||
108 | RO read only value | ||
109 | RW read/write value | ||
110 | |||
111 | All thermal sysfs attributes will be represented under /sys/class/thermal | ||
112 | /sys/class/thermal/ | ||
113 | |||
114 | Thermal zone device sys I/F, created once it's registered: | ||
115 | |thermal_zone[0-*]: | ||
116 | |-----type: Type of the thermal zone | ||
117 | |-----temp: Current temperature | ||
118 | |-----mode: Working mode of the thermal zone | ||
119 | |-----trip_point_[0-*]_temp: Trip point temperature | ||
120 | |-----trip_point_[0-*]_type: Trip point type | ||
121 | |||
122 | Thermal cooling device sys I/F, created once it's registered: | ||
123 | |cooling_device[0-*]: | ||
124 | |-----type : Type of the cooling device(processor/fan/...) | ||
125 | |-----max_state: Maximum cooling state of the cooling device | ||
126 | |-----cur_state: Current cooling state of the cooling device | ||
127 | |||
128 | |||
129 | These two dynamic attributes are created/removed in pairs. | ||
130 | They represent the relationship between a thermal zone and its associated cooling device. | ||
131 | They are created/removed for each | ||
132 | thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device successful exection. | ||
133 | |||
134 | |thermal_zone[0-*] | ||
135 | |-----cdev[0-*]: The [0-*]th cooling device in the current thermal zone | ||
136 | |-----cdev[0-*]_trip_point: Trip point that cdev[0-*] is associated with | ||
137 | |||
138 | |||
139 | *************************** | ||
140 | * Thermal zone attributes * | ||
141 | *************************** | ||
142 | |||
143 | type Strings which represent the thermal zone type. | ||
144 | This is given by thermal zone driver as part of registration. | ||
145 | Eg: "ACPI thermal zone" indicates it's a ACPI thermal device | ||
146 | RO | ||
147 | Optional | ||
148 | |||
149 | temp Current temperature as reported by thermal zone (sensor) | ||
150 | Unit: degree celsius | ||
151 | RO | ||
152 | Required | ||
153 | |||
154 | mode One of the predifned values in [kernel, user] | ||
155 | This file gives information about the algorithm | ||
156 | that is currently managing the thermal zone. | ||
157 | It can be either default kernel based algorithm | ||
158 | or user space application. | ||
159 | RW | ||
160 | Optional | ||
161 | kernel = Thermal management in kernel thermal zone driver. | ||
162 | user = Preventing kernel thermal zone driver actions upon | ||
163 | trip points so that user application can take full | ||
164 | charge of the thermal management. | ||
165 | |||
166 | trip_point_[0-*]_temp The temperature above which trip point will be fired | ||
167 | Unit: degree celsius | ||
168 | RO | ||
169 | Optional | ||
170 | |||
171 | trip_point_[0-*]_type Strings which indicate the type of the trip point | ||
172 | Eg. it can be one of critical, hot, passive, | ||
173 | active[0-*] for ACPI thermal zone. | ||
174 | RO | ||
175 | Optional | ||
176 | |||
177 | cdev[0-*] Sysfs link to the thermal cooling device node where the sys I/F | ||
178 | for cooling device throttling control represents. | ||
179 | RO | ||
180 | Optional | ||
181 | |||
182 | cdev[0-*]_trip_point The trip point with which cdev[0-*] is assocated in this thermal zone | ||
183 | -1 means the cooling device is not associated with any trip point. | ||
184 | RO | ||
185 | Optional | ||
186 | |||
187 | ****************************** | ||
188 | * Cooling device attributes * | ||
189 | ****************************** | ||
190 | |||
191 | type String which represents the type of device | ||
192 | eg: For generic ACPI: this should be "Fan", | ||
193 | "Processor" or "LCD" | ||
194 | eg. For memory controller device on intel_menlow platform: | ||
195 | this should be "Memory controller" | ||
196 | RO | ||
197 | Optional | ||
198 | |||
199 | max_state The maximum permissible cooling state of this cooling device. | ||
200 | RO | ||
201 | Required | ||
202 | |||
203 | cur_state The current cooling state of this cooling device. | ||
204 | the value can any integer numbers between 0 and max_state, | ||
205 | cur_state == 0 means no cooling | ||
206 | cur_state == max_state means the maximum cooling. | ||
207 | RW | ||
208 | Required | ||
209 | |||
210 | 3. A simple implementation | ||
211 | |||
212 | ACPI thermal zone may support multiple trip points like critical/hot/passive/active. | ||
213 | If an ACPI thermal zone supports critical, passive, active[0] and active[1] at the same time, | ||
214 | it may register itself as a thermale_zone_device (thermal_zone1) with 4 trip points in all. | ||
215 | It has one processor and one fan, which are both registered as thermal_cooling_device. | ||
216 | If the processor is listed in _PSL method, and the fan is listed in _AL0 method, | ||
217 | the sys I/F structure will be built like this: | ||
218 | |||
219 | /sys/class/thermal: | ||
220 | |||
221 | |thermal_zone1: | ||
222 | |-----type: ACPI thermal zone | ||
223 | |-----temp: 37 | ||
224 | |-----mode: kernel | ||
225 | |-----trip_point_0_temp: 100 | ||
226 | |-----trip_point_0_type: critical | ||
227 | |-----trip_point_1_temp: 80 | ||
228 | |-----trip_point_1_type: passive | ||
229 | |-----trip_point_2_temp: 70 | ||
230 | |-----trip_point_2_type: active[0] | ||
231 | |-----trip_point_3_temp: 60 | ||
232 | |-----trip_point_3_type: active[1] | ||
233 | |-----cdev0: --->/sys/class/thermal/cooling_device0 | ||
234 | |-----cdev0_trip_point: 1 /* cdev0 can be used for passive */ | ||
235 | |-----cdev1: --->/sys/class/thermal/cooling_device3 | ||
236 | |-----cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/ | ||
237 | |||
238 | |cooling_device0: | ||
239 | |-----type: Processor | ||
240 | |-----max_state: 8 | ||
241 | |-----cur_state: 0 | ||
242 | |||
243 | |cooling_device3: | ||
244 | |-----type: Fan | ||
245 | |-----max_state: 2 | ||
246 | |-----cur_state: 0 | ||