Documentation/thermal/sysfs-api.txt - kernel/common - Git at Google

 Generic Thermal Sysfs driver How To
 =========================

 Written by Sujith Thomas <[email protected]>, Zhang Rui <[email protected]>

 Updated: 2 January 2008

 Copyright (c)  2008 Intel Corporation


 0. Introduction

 The generic thermal sysfs provides a set of interfaces for thermal zone devices (sensors)
 and thermal cooling devices (fan, processor...) to register with the thermal management
 solution and to be a part of it.

 This how-to focuses on enabling new thermal zone and cooling devices to participate
 in thermal management.
 This solution is platform independent and any type of thermal zone devices and
 cooling devices should be able to make use of the infrastructure.

 The main task of the thermal sysfs driver is to expose thermal zone attributes as well
 as cooling device attributes to the user space.
 An intelligent thermal management application can make decisions based on inputs
 from thermal zone attributes (the current temperature and trip point temperature)
 and throttle appropriate devices.

 [0-*]	denotes any positive number starting from 0
 [1-*]	denotes any positive number starting from 1

 1. thermal sysfs driver interface functions

 1.1 thermal zone device interface
 1.1.1 struct thermal_zone_device *thermal_zone_device_register(char *name, int trips,
 				void *devdata, struct thermal_zone_device_ops *ops)

 	This interface function adds a new thermal zone device (sensor) to
 	/sys/class/thermal folder as thermal_zone[0-*].
 	It tries to bind all the thermal cooling devices registered at the same time.

 	name: the thermal zone name.
 	trips: the total number of trip points this thermal zone supports.
 	devdata: device private data
 	ops: thermal zone device call-backs.
 		.bind: bind the thermal zone device with a thermal cooling device.
 		.unbind: unbind the thermal zone device with a thermal cooling device.
 		.get_temp: get the current temperature of the thermal zone.
 		.get_mode: get the current mode (user/kernel) of the thermal zone.
 			   "kernel" means thermal management is done in kernel.
 			   "user" will prevent kernel thermal driver actions upon trip points
 			   so that user applications can take charge of thermal management.
 		.set_mode: set the mode (user/kernel) of the thermal zone.
 		.get_trip_type: get the type of certain trip point.
 		.get_trip_temp: get the temperature above which the certain trip point
 				will be fired.

 1.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz)

 	This interface function removes the thermal zone device.
 	It deletes the corresponding entry form /sys/class/thermal folder and unbind all
 	the thermal cooling devices it uses.

 1.2 thermal cooling device interface
 1.2.1 struct thermal_cooling_device *thermal_cooling_device_register(char *name,
 					void *devdata, struct thermal_cooling_device_ops *)

 	This interface function adds a new thermal cooling device (fan/processor/...) to
 	/sys/class/thermal/ folder as cooling_device[0-*].
 	It tries to bind itself to all the thermal zone devices register at the same time.
 	name: the cooling device name.
 	devdata: device private data.
 	ops: thermal cooling devices call-backs.
 		.get_max_state: get the Maximum throttle state of the cooling device.
 		.get_cur_state: get the Current throttle state of the cooling device.
 		.set_cur_state: set the Current throttle state of the cooling device.

 1.2.2 void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev)

 	This interface function remove the thermal cooling device.
 	It deletes the corresponding entry form /sys/class/thermal folder and unbind
 	itself from all	the thermal zone devices using it.

 1.3 interface for binding a thermal zone device with a thermal cooling device
 1.3.1 int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
 			int trip, struct thermal_cooling_device *cdev);

 	This interface function bind a thermal cooling device to the certain trip point
 	of a thermal zone device.
 	This function is usually called in the thermal zone device .bind callback.
 	tz: the thermal zone device
 	cdev: thermal cooling device
 	trip: indicates which trip point the cooling devices is associated with
 		 in this thermal zone.

 1.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz,
 				int trip, struct thermal_cooling_device *cdev);

 	This interface function unbind a thermal cooling device from the certain trip point
 	of a thermal zone device.
 	This function is usually called in the thermal zone device .unbind callback.
 	tz: the thermal zone device
 	cdev: thermal cooling device
 	trip: indicates which trip point the cooling devices is associated with
 		in this thermal zone.

 2. sysfs attributes structure

 RO	read only value
 RW	read/write value

 All thermal sysfs attributes will be represented under /sys/class/thermal

 Thermal zone device sys I/F, created once it's registered:
 |thermal_zone[0-*]:
 	|-----type:			Type of the thermal zone
 	|-----temp:			Current temperature
 	|-----mode:			Working mode of the thermal zone
 	|-----trip_point_[0-*]_temp:	Trip point temperature
 	|-----trip_point_[0-*]_type:	Trip point type

 Thermal cooling device sys I/F, created once it's registered:
 |cooling_device[0-*]:
 	|-----type :			Type of the cooling device(processor/fan/...)
 	|-----max_state:		Maximum cooling state of the cooling device
 	|-----cur_state:		Current cooling state of the cooling device


 These two dynamic attributes are created/removed in pairs.
 They represent the relationship between a thermal zone and its associated cooling device.
 They are created/removed for each
 thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device successful execution.

 |thermal_zone[0-*]
 	|-----cdev[0-*]:		The [0-*]th cooling device in the current thermal zone
 	|-----cdev[0-*]_trip_point:	Trip point that cdev[0-*] is associated with


 ***************************
 * Thermal zone attributes *
 ***************************

 type				Strings which represent the thermal zone type.
 				This is given by thermal zone driver as part of registration.
 				Eg: "ACPI thermal zone" indicates it's a ACPI thermal device
 				RO
 				Optional

 temp				Current temperature as reported by thermal zone (sensor)
 				Unit: degree Celsius
 				RO
 				Required

 mode				One of the predefined values in [kernel, user]
 				This file gives information about the algorithm
 				that is currently managing the thermal zone.
 				It can be either default kernel based algorithm
 				or user space application.
 				RW
 				Optional
 				kernel	= Thermal management in kernel thermal zone driver.
 				user	= Preventing kernel thermal zone driver actions upon
 					  trip points so that user application can take full
 					  charge of the thermal management.

 trip_point_[0-*]_temp		The temperature above which trip point will be fired
 				Unit: degree Celsius
 				RO
 				Optional

 trip_point_[0-*]_type 		Strings which indicate the type of the trip point
 				E.g. it can be one of critical, hot, passive,
 				    active[0-*] for ACPI thermal zone.
 				RO
 				Optional

 cdev[0-*]			Sysfs link to the thermal cooling device node where the sys I/F
 				for cooling device throttling control represents.
 				RO
 				Optional

 cdev[0-*]_trip_point		The trip point with which cdev[0-*] is associated in this thermal zone
 				-1 means the cooling device is not associated with any trip point.
 				RO
 				Optional

 ******************************
 * Cooling device  attributes *
 ******************************

 type				String which represents the type of device
 				eg: For generic ACPI: this should be "Fan",
 				"Processor" or "LCD"
 				eg. For memory controller device on intel_menlow platform:
 				this should be "Memory controller"
 				RO
 				Optional

 max_state			The maximum permissible cooling state of this cooling device.
 				RO
 				Required

 cur_state			The current cooling state of this cooling device.
 				the value can any integer numbers between 0 and max_state,
 				cur_state == 0 means no cooling
 				cur_state == max_state means the maximum cooling.
 				RW
 				Required

 3. A simple implementation

 ACPI thermal zone may support multiple trip points like critical/hot/passive/active.
 If an ACPI thermal zone supports critical, passive, active[0] and active[1] at the same time,
 it may register itself as a thermal_zone_device (thermal_zone1) with 4 trip points in all.
 It has one processor and one fan, which are both registered as thermal_cooling_device.
 If the processor is listed in _PSL method, and the fan is listed in _AL0 method,
 the sys I/F structure will be built like this:

 /sys/class/thermal:

 |thermal_zone1:
 	|-----type:			ACPI thermal zone
 	|-----temp:			37
 	|-----mode:			kernel
 	|-----trip_point_0_temp:	100
 	|-----trip_point_0_type:	critical
 	|-----trip_point_1_temp:	80
 	|-----trip_point_1_type:	passive
 	|-----trip_point_2_temp:	70
 	|-----trip_point_2_type:	active[0]
 	|-----trip_point_3_temp:	60
 	|-----trip_point_3_type:	active[1]
 	|-----cdev0:			--->/sys/class/thermal/cooling_device0
 	|-----cdev0_trip_point:		1	/* cdev0 can be used for passive */
 	|-----cdev1:			--->/sys/class/thermal/cooling_device3
 	|-----cdev1_trip_point:		2	/* cdev1 can be used for active[0]*/

 |cooling_device0:
 	|-----type:			Processor
 	|-----max_state:		8
 	|-----cur_state:		0

 |cooling_device3:
 	|-----type:			Fan
 	|-----max_state:		2
 	|-----cur_state:		0
	Generic Thermal Sysfs driver How To
	=========================

	Written by Sujith Thomas <[email protected]>, Zhang Rui <[email protected]>

	Updated: 2 January 2008

	Copyright (c) 2008 Intel Corporation


	0. Introduction

	The generic thermal sysfs provides a set of interfaces for thermal zone devices (sensors)
	and thermal cooling devices (fan, processor...) to register with the thermal management
	solution and to be a part of it.

	This how-to focuses on enabling new thermal zone and cooling devices to participate
	in thermal management.
	This solution is platform independent and any type of thermal zone devices and
	cooling devices should be able to make use of the infrastructure.

	The main task of the thermal sysfs driver is to expose thermal zone attributes as well
	as cooling device attributes to the user space.
	An intelligent thermal management application can make decisions based on inputs
	from thermal zone attributes (the current temperature and trip point temperature)
	and throttle appropriate devices.

	[0-*] denotes any positive number starting from 0
	[1-*] denotes any positive number starting from 1

	1. thermal sysfs driver interface functions

	1.1 thermal zone device interface
	1.1.1 struct thermal_zone_device thermal_zone_device_register(char name, int trips,
	void devdata, struct thermal_zone_device_ops ops)

	This interface function adds a new thermal zone device (sensor) to
	/sys/class/thermal folder as thermal_zone[0-*].
	It tries to bind all the thermal cooling devices registered at the same time.

	name: the thermal zone name.
	trips: the total number of trip points this thermal zone supports.
	devdata: device private data
	ops: thermal zone device call-backs.
	.bind: bind the thermal zone device with a thermal cooling device.
	.unbind: unbind the thermal zone device with a thermal cooling device.
	.get_temp: get the current temperature of the thermal zone.
	.get_mode: get the current mode (user/kernel) of the thermal zone.
	"kernel" means thermal management is done in kernel.
	"user" will prevent kernel thermal driver actions upon trip points
	so that user applications can take charge of thermal management.
	.set_mode: set the mode (user/kernel) of the thermal zone.
	.get_trip_type: get the type of certain trip point.
	.get_trip_temp: get the temperature above which the certain trip point
	will be fired.

	1.1.2 void thermal_zone_device_unregister(struct thermal_zone_device *tz)

	This interface function removes the thermal zone device.
	It deletes the corresponding entry form /sys/class/thermal folder and unbind all
	the thermal cooling devices it uses.

	1.2 thermal cooling device interface
	1.2.1 struct thermal_cooling_device thermal_cooling_device_register(char name,
	void devdata, struct thermal_cooling_device_ops )

	This interface function adds a new thermal cooling device (fan/processor/...) to
	/sys/class/thermal/ folder as cooling_device[0-*].
	It tries to bind itself to all the thermal zone devices register at the same time.
	name: the cooling device name.
	devdata: device private data.
	ops: thermal cooling devices call-backs.
	.get_max_state: get the Maximum throttle state of the cooling device.
	.get_cur_state: get the Current throttle state of the cooling device.
	.set_cur_state: set the Current throttle state of the cooling device.

	1.2.2 void thermal_cooling_device_unregister(struct thermal_cooling_device *cdev)

	This interface function remove the thermal cooling device.
	It deletes the corresponding entry form /sys/class/thermal folder and unbind
	itself from all the thermal zone devices using it.

	1.3 interface for binding a thermal zone device with a thermal cooling device
	1.3.1 int thermal_zone_bind_cooling_device(struct thermal_zone_device *tz,
	int trip, struct thermal_cooling_device *cdev);

	This interface function bind a thermal cooling device to the certain trip point
	of a thermal zone device.
	This function is usually called in the thermal zone device .bind callback.
	tz: the thermal zone device
	cdev: thermal cooling device
	trip: indicates which trip point the cooling devices is associated with
	in this thermal zone.

	1.3.2 int thermal_zone_unbind_cooling_device(struct thermal_zone_device *tz,
	int trip, struct thermal_cooling_device *cdev);

	This interface function unbind a thermal cooling device from the certain trip point
	of a thermal zone device.
	This function is usually called in the thermal zone device .unbind callback.
	tz: the thermal zone device
	cdev: thermal cooling device
	trip: indicates which trip point the cooling devices is associated with
	in this thermal zone.

	2. sysfs attributes structure

	RO read only value
	RW read/write value

	All thermal sysfs attributes will be represented under /sys/class/thermal

	Thermal zone device sys I/F, created once it's registered:
	\|thermal_zone[0-*]:
	\|-----type: Type of the thermal zone
	\|-----temp: Current temperature
	\|-----mode: Working mode of the thermal zone
	\|-----trip_point_[0-*]_temp: Trip point temperature
	\|-----trip_point_[0-*]_type: Trip point type

	Thermal cooling device sys I/F, created once it's registered:
	\|cooling_device[0-*]:
	\|-----type : Type of the cooling device(processor/fan/...)
	\|-----max_state: Maximum cooling state of the cooling device
	\|-----cur_state: Current cooling state of the cooling device


	These two dynamic attributes are created/removed in pairs.
	They represent the relationship between a thermal zone and its associated cooling device.
	They are created/removed for each
	thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device successful execution.

	\|thermal_zone[0-*]
	\|-----cdev[0-]: The [0-]th cooling device in the current thermal zone
	\|-----cdev[0-]_trip_point: Trip point that cdev[0-] is associated with


	***************************
	* Thermal zone attributes *
	***************************

	type Strings which represent the thermal zone type.
	This is given by thermal zone driver as part of registration.
	Eg: "ACPI thermal zone" indicates it's a ACPI thermal device
	RO
	Optional

	temp Current temperature as reported by thermal zone (sensor)
	Unit: degree Celsius
	RO
	Required

	mode One of the predefined values in [kernel, user]
	This file gives information about the algorithm
	that is currently managing the thermal zone.
	It can be either default kernel based algorithm
	or user space application.
	RW
	Optional
	kernel = Thermal management in kernel thermal zone driver.
	user = Preventing kernel thermal zone driver actions upon
	trip points so that user application can take full
	charge of the thermal management.

	trip_point_[0-*]_temp The temperature above which trip point will be fired
	Unit: degree Celsius
	RO
	Optional

	trip_point_[0-*]_type Strings which indicate the type of the trip point
	E.g. it can be one of critical, hot, passive,
	active[0-*] for ACPI thermal zone.
	RO
	Optional

	cdev[0-*] Sysfs link to the thermal cooling device node where the sys I/F
	for cooling device throttling control represents.
	RO
	Optional

	cdev[0-]_trip_point The trip point with which cdev[0-] is associated in this thermal zone
	-1 means the cooling device is not associated with any trip point.
	RO
	Optional

	******************************
	* Cooling device attributes *
	******************************

	type String which represents the type of device
	eg: For generic ACPI: this should be "Fan",
	"Processor" or "LCD"
	eg. For memory controller device on intel_menlow platform:
	this should be "Memory controller"
	RO
	Optional

	max_state The maximum permissible cooling state of this cooling device.
	RO
	Required

	cur_state The current cooling state of this cooling device.
	the value can any integer numbers between 0 and max_state,
	cur_state == 0 means no cooling
	cur_state == max_state means the maximum cooling.
	RW
	Required

	3. A simple implementation

	ACPI thermal zone may support multiple trip points like critical/hot/passive/active.
	If an ACPI thermal zone supports critical, passive, active[0] and active[1] at the same time,
	it may register itself as a thermal_zone_device (thermal_zone1) with 4 trip points in all.
	It has one processor and one fan, which are both registered as thermal_cooling_device.
	If the processor is listed in _PSL method, and the fan is listed in _AL0 method,
	the sys I/F structure will be built like this:

	/sys/class/thermal:

	\|thermal_zone1:
	\|-----type: ACPI thermal zone
	\|-----temp: 37
	\|-----mode: kernel
	\|-----trip_point_0_temp: 100
	\|-----trip_point_0_type: critical
	\|-----trip_point_1_temp: 80
	\|-----trip_point_1_type: passive
	\|-----trip_point_2_temp: 70
	\|-----trip_point_2_type: active[0]
	\|-----trip_point_3_temp: 60
	\|-----trip_point_3_type: active[1]
	\|-----cdev0: --->/sys/class/thermal/cooling_device0
	\|-----cdev0_trip_point: 1 /* cdev0 can be used for passive */
	\|-----cdev1: --->/sys/class/thermal/cooling_device3
	\|-----cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/

	\|cooling_device0:
	\|-----type: Processor
	\|-----max_state: 8
	\|-----cur_state: 0

	\|cooling_device3:
	\|-----type: Fan
	\|-----max_state: 2
	\|-----cur_state: 0