Documentation/thermal/sysfs-api.txt

   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 focuses 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 call-backs.
  45                 .bind: bind the thermal zone device with a thermal cooling device.
  46                 .unbind: unbind 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 call-backs.
  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
 113 Thermal zone device sys I/F, created once it's registered:
 114 |thermal_zone[0-*]:
 115         |-----type:                     Type of the thermal zone
 116         |-----temp:                     Current temperature
 117         |-----mode:                     Working mode of the thermal zone
 118         |-----trip_point_[0-*]_temp:    Trip point temperature
 119         |-----trip_point_[0-*]_type:    Trip point type
 120
 121 Thermal cooling device sys I/F, created once it's registered:
 122 |cooling_device[0-*]:
 123         |-----type :                    Type of the cooling device(processor/fan/...)
 124         |-----max_state:                Maximum cooling state of the cooling device
 125         |-----cur_state:                Current cooling state of the cooling device
 126
 127
 128 These two dynamic attributes are created/removed in pairs.
 129 They represent the relationship between a thermal zone and its associated cooling device.
 130 They are created/removed for each
 131 thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device successful execution.
 132
 133 |thermal_zone[0-*]
 134         |-----cdev[0-*]:                The [0-*]th cooling device in the current thermal zone
 135         |-----cdev[0-*]_trip_point:     Trip point that cdev[0-*] is associated with
 136
 137
 138 ***************************
 139 * Thermal zone attributes *
 140 ***************************
 141
 142 type                            Strings which represent the thermal zone type.
 143                                 This is given by thermal zone driver as part of registration.
 144                                 Eg: "ACPI thermal zone" indicates it's a ACPI thermal device
 145                                 RO
 146 <<<<<<< HEAD:Documentation/thermal/sysfs-api.txt
 147                                 Optional
 148 =======
 149                                 Required
 150 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:Documentation/thermal/sysfs-api.txt
 151
 152 temp                            Current temperature as reported by thermal zone (sensor)
 153 <<<<<<< HEAD:Documentation/thermal/sysfs-api.txt
 154                                 Unit: degree Celsius
 155 =======
 156                                 Unit: millidegree Celsius
 157 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:Documentation/thermal/sysfs-api.txt
 158                                 RO
 159                                 Required
 160
 161 mode                            One of the predefined values in [kernel, user]
 162                                 This file gives information about the algorithm
 163                                 that is currently managing the thermal zone.
 164                                 It can be either default kernel based algorithm
 165                                 or user space application.
 166                                 RW
 167                                 Optional
 168                                 kernel  = Thermal management in kernel thermal zone driver.
 169                                 user    = Preventing kernel thermal zone driver actions upon
 170                                           trip points so that user application can take full
 171                                           charge of the thermal management.
 172
 173 trip_point_[0-*]_temp           The temperature above which trip point will be fired
 174 <<<<<<< HEAD:Documentation/thermal/sysfs-api.txt
 175                                 Unit: degree Celsius
 176 =======
 177                                 Unit: millidegree Celsius
 178 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:Documentation/thermal/sysfs-api.txt
 179                                 RO
 180                                 Optional
 181
 182 trip_point_[0-*]_type           Strings which indicate the type of the trip point
 183                                 E.g. it can be one of critical, hot, passive,
 184                                     active[0-*] for ACPI thermal zone.
 185                                 RO
 186                                 Optional
 187
 188 cdev[0-*]                       Sysfs link to the thermal cooling device node where the sys I/F
 189                                 for cooling device throttling control represents.
 190                                 RO
 191                                 Optional
 192
 193 cdev[0-*]_trip_point            The trip point with which cdev[0-*] is associated in this thermal zone
 194                                 -1 means the cooling device is not associated with any trip point.
 195                                 RO
 196                                 Optional
 197
 198 ******************************
 199 * Cooling device  attributes *
 200 ******************************
 201
 202 type                            String which represents the type of device
 203                                 eg: For generic ACPI: this should be "Fan",
 204                                 "Processor" or "LCD"
 205                                 eg. For memory controller device on intel_menlow platform:
 206                                 this should be "Memory controller"
 207                                 RO
 208 <<<<<<< HEAD:Documentation/thermal/sysfs-api.txt
 209                                 Optional
 210 =======
 211                                 Required
 212 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:Documentation/thermal/sysfs-api.txt
 213
 214 max_state                       The maximum permissible cooling state of this cooling device.
 215                                 RO
 216                                 Required
 217
 218 cur_state                       The current cooling state of this cooling device.
 219                                 the value can any integer numbers between 0 and max_state,
 220                                 cur_state == 0 means no cooling
 221                                 cur_state == max_state means the maximum cooling.
 222                                 RW
 223                                 Required
 224
 225 3. A simple implementation
 226
 227 ACPI thermal zone may support multiple trip points like critical/hot/passive/active.
 228 If an ACPI thermal zone supports critical, passive, active[0] and active[1] at the same time,
 229 it may register itself as a thermal_zone_device (thermal_zone1) with 4 trip points in all.
 230 It has one processor and one fan, which are both registered as thermal_cooling_device.
 231 If the processor is listed in _PSL method, and the fan is listed in _AL0 method,
 232 the sys I/F structure will be built like this:
 233
 234 /sys/class/thermal:
 235
 236 |thermal_zone1:
 237         |-----type:                     ACPI thermal zone
 238 <<<<<<< HEAD:Documentation/thermal/sysfs-api.txt
 239         |-----temp:                     37
 240 =======
 241         |-----temp:                     37000
 242 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:Documentation/thermal/sysfs-api.txt
 243         |-----mode:                     kernel
 244 <<<<<<< HEAD:Documentation/thermal/sysfs-api.txt
 245         |-----trip_point_0_temp:        100
 246 =======
 247         |-----trip_point_0_temp:        100000
 248 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:Documentation/thermal/sysfs-api.txt
 249         |-----trip_point_0_type:        critical
 250 <<<<<<< HEAD:Documentation/thermal/sysfs-api.txt
 251         |-----trip_point_1_temp:        80
 252 =======
 253         |-----trip_point_1_temp:        80000
 254 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:Documentation/thermal/sysfs-api.txt
 255         |-----trip_point_1_type:        passive
 256 <<<<<<< HEAD:Documentation/thermal/sysfs-api.txt
 257         |-----trip_point_2_temp:        70
 258         |-----trip_point_2_type:        active[0]
 259         |-----trip_point_3_temp:        60
 260         |-----trip_point_3_type:        active[1]
 261 =======
 262         |-----trip_point_2_temp:        70000
 263         |-----trip_point_2_type:        active0
 264         |-----trip_point_3_temp:        60000
 265         |-----trip_point_3_type:        active1
 266 >>>>>>> 264e3e889d86e552b4191d69bb60f4f3b383135a:Documentation/thermal/sysfs-api.txt
 267         |-----cdev0:                    --->/sys/class/thermal/cooling_device0
 268         |-----cdev0_trip_point:         1       /* cdev0 can be used for passive */
 269         |-----cdev1:                    --->/sys/class/thermal/cooling_device3
 270         |-----cdev1_trip_point:         2       /* cdev1 can be used for active[0]*/
 271
 272 |cooling_device0:
 273         |-----type:                     Processor
 274         |-----max_state:                8
 275         |-----cur_state:                0
 276
 277 |cooling_device3:
 278         |-----type:                     Fan
 279         |-----max_state:                2
 280         |-----cur_state:                0