[linux-2.6-block.git] / Documentation / thermal / sysfs-api.txt

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

Written by Sujith Thomas <sujith.thomas@intel.com>, Zhang Rui <rui.zhang@intel.com>

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

Thermal sysfs attributes will be represented under /sys/class/thermal.
Hwmon sysfs I/F extension is also available under /sys/class/hwmon
if hwmon is compiled in or built as a module.

Thermal zone device sys I/F, created once it's registered:
/sys/class/thermal/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:
/sys/class/thermal/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.

/sys/class/thermal/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

Besides the thermal zone device sysfs I/F and cooling device sysfs I/F,
the generic thermal driver also creates a hwmon sysfs I/F for each _type_ of
thermal zone device. E.g. the generic thermal driver registers one hwmon class device
and build the associated hwmon sysfs I/F for all the registered ACPI thermal zones.
/sys/class/hwmon/hwmon[0-*]:
	|-----name:			The type of the thermal zone devices.
	|-----temp[1-*]_input:		The current temperature of thermal zone [1-*].
	|-----temp[1-*]_critical:	The critical trip point of thermal zone [1-*].
Please read Documentation/hwmon/sysfs-interface for additional information.

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

type				Strings which represent the thermal zone type.
				This is given by thermal zone driver as part of registration.
				Eg: "acpitz" indicates it's an ACPI thermal device.
				In order to keep it consistent with hwmon sys attribute,
				this should be a short, lowercase string,
				not containing spaces nor dashes.
				RO
				Required

temp				Current temperature as reported by thermal zone (sensor)
				Unit: millidegree 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: millidegree 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
				Required

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:			acpitz
	|-----temp:			37000
	|-----mode:			kernel
	|-----trip_point_0_temp:	100000
	|-----trip_point_0_type:	critical
	|-----trip_point_1_temp:	80000
	|-----trip_point_1_type:	passive
	|-----trip_point_2_temp:	70000
	|-----trip_point_2_type:	active0
	|-----trip_point_3_temp:	60000
	|-----trip_point_3_type:	active1
	|-----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

/sys/class/hwmon:

|hwmon0:
	|-----name:			acpitz
	|-----temp1_input:		37000
	|-----temp1_crit:		100000
Commit	Line	Data
203d3d4a ZR	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
543a9561	17	This how-to focuses on enabling new thermal zone and cooling devices to participate
203d3d4a ZR	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
543a9561	44	ops: thermal zone device call-backs.
203d3d4a	45	.bind: bind the thermal zone device with a thermal cooling device.
543a9561	46	.unbind: unbind the thermal zone device with a thermal cooling device.
203d3d4a ZR	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.
543a9561	72	ops: thermal cooling devices call-backs.
203d3d4a ZR	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
e9ae7107 ZR	111	Thermal sysfs attributes will be represented under /sys/class/thermal.
	112	Hwmon sysfs I/F extension is also available under /sys/class/hwmon
	113	if hwmon is compiled in or built as a module.
203d3d4a ZR	114
203d3d4a ZR	115	Thermal zone device sys I/F, created once it's registered:
e9ae7107	116	/sys/class/thermal/thermal_zone[0-*]:
203d3d4a ZR	117	\|-----type: Type of the thermal zone
	118	\|-----temp: Current temperature
	119	\|-----mode: Working mode of the thermal zone
	120	\|-----trip_point_[0-*]_temp: Trip point temperature
	121	\|-----trip_point_[0-*]_type: Trip point type
	122
	123	Thermal cooling device sys I/F, created once it's registered:
e9ae7107	124	/sys/class/thermal/cooling_device[0-*]:
203d3d4a ZR	125	\|-----type : Type of the cooling device(processor/fan/...)
	126	\|-----max_state: Maximum cooling state of the cooling device
	127	\|-----cur_state: Current cooling state of the cooling device
	128
	129
	130	These two dynamic attributes are created/removed in pairs.
	131	They represent the relationship between a thermal zone and its associated cooling device.
	132	They are created/removed for each
543a9561	133	thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device successful execution.
203d3d4a	134
e9ae7107	135	/sys/class/thermal/thermal_zone[0-*]
203d3d4a ZR	136	\|-----cdev[0-]: The [0-]th cooling device in the current thermal zone
	137	\|-----cdev[0-]_trip_point: Trip point that cdev[0-] is associated with
	138
e9ae7107 ZR	139	Besides the thermal zone device sysfs I/F and cooling device sysfs I/F,
	140	the generic thermal driver also creates a hwmon sysfs I/F for each _type_ of
	141	thermal zone device. E.g. the generic thermal driver registers one hwmon class device
	142	and build the associated hwmon sysfs I/F for all the registered ACPI thermal zones.
	143	/sys/class/hwmon/hwmon[0-*]:
	144	\|-----name: The type of the thermal zone devices.
	145	\|-----temp[1-]_input: The current temperature of thermal zone [1-].
	146	\|-----temp[1-]_critical: The critical trip point of thermal zone [1-].
	147	Please read Documentation/hwmon/sysfs-interface for additional information.
203d3d4a ZR	148
	149	***************************
	150	* Thermal zone attributes *
	151	***************************
	152
	153	type Strings which represent the thermal zone type.
	154	This is given by thermal zone driver as part of registration.
e9ae7107 ZR	155	Eg: "acpitz" indicates it's an ACPI thermal device.
	156	In order to keep it consistent with hwmon sys attribute,
	157	this should be a short, lowercase string,
	158	not containing spaces nor dashes.
203d3d4a	159	RO
3152fb9f	160	Required
203d3d4a ZR	161
203d3d4a ZR	162	temp Current temperature as reported by thermal zone (sensor)
3152fb9f	163	Unit: millidegree Celsius
203d3d4a ZR	164	RO
	165	Required
	166
543a9561	167	mode One of the predefined values in [kernel, user]
203d3d4a ZR	168	This file gives information about the algorithm
	169	that is currently managing the thermal zone.
	170	It can be either default kernel based algorithm
	171	or user space application.
	172	RW
	173	Optional
	174	kernel = Thermal management in kernel thermal zone driver.
	175	user = Preventing kernel thermal zone driver actions upon
	176	trip points so that user application can take full
	177	charge of the thermal management.
	178
	179	trip_point_[0-*]_temp The temperature above which trip point will be fired
3152fb9f	180	Unit: millidegree Celsius
203d3d4a ZR	181	RO
	182	Optional
	183
	184	trip_point_[0-*]_type Strings which indicate the type of the trip point
543a9561	185	E.g. it can be one of critical, hot, passive,
203d3d4a ZR	186	active[0-*] for ACPI thermal zone.
	187	RO
	188	Optional
	189
	190	cdev[0-*] Sysfs link to the thermal cooling device node where the sys I/F
	191	for cooling device throttling control represents.
	192	RO
	193	Optional
	194
543a9561	195	cdev[0-]_trip_point The trip point with which cdev[0-] is associated in this thermal zone
203d3d4a ZR	196	-1 means the cooling device is not associated with any trip point.
	197	RO
	198	Optional
	199
	200	******************************
	201	* Cooling device attributes *
	202	******************************
	203
	204	type String which represents the type of device
	205	eg: For generic ACPI: this should be "Fan",
	206	"Processor" or "LCD"
	207	eg. For memory controller device on intel_menlow platform:
	208	this should be "Memory controller"
	209	RO
3152fb9f	210	Required
203d3d4a ZR	211
	212	max_state The maximum permissible cooling state of this cooling device.
	213	RO
	214	Required
	215
	216	cur_state The current cooling state of this cooling device.
	217	the value can any integer numbers between 0 and max_state,
	218	cur_state == 0 means no cooling
	219	cur_state == max_state means the maximum cooling.
	220	RW
	221	Required
	222
	223	3. A simple implementation
	224
	225	ACPI thermal zone may support multiple trip points like critical/hot/passive/active.
	226	If an ACPI thermal zone supports critical, passive, active[0] and active[1] at the same time,
543a9561	227	it may register itself as a thermal_zone_device (thermal_zone1) with 4 trip points in all.
203d3d4a ZR	228	It has one processor and one fan, which are both registered as thermal_cooling_device.
	229	If the processor is listed in _PSL method, and the fan is listed in _AL0 method,
	230	the sys I/F structure will be built like this:
	231
	232	/sys/class/thermal:
	233
	234	\|thermal_zone1:
e9ae7107	235	\|-----type: acpitz
3152fb9f	236	\|-----temp: 37000
203d3d4a	237	\|-----mode: kernel
3152fb9f	238	\|-----trip_point_0_temp: 100000
203d3d4a	239	\|-----trip_point_0_type: critical
3152fb9f	240	\|-----trip_point_1_temp: 80000
203d3d4a	241	\|-----trip_point_1_type: passive
3152fb9f ZR	242	\|-----trip_point_2_temp: 70000
	243	\|-----trip_point_2_type: active0
	244	\|-----trip_point_3_temp: 60000
	245	\|-----trip_point_3_type: active1
203d3d4a ZR	246	\|-----cdev0: --->/sys/class/thermal/cooling_device0
	247	\|-----cdev0_trip_point: 1 /* cdev0 can be used for passive */
	248	\|-----cdev1: --->/sys/class/thermal/cooling_device3
	249	\|-----cdev1_trip_point: 2 /* cdev1 can be used for active[0]*/
	250
	251	\|cooling_device0:
	252	\|-----type: Processor
	253	\|-----max_state: 8
	254	\|-----cur_state: 0
	255
	256	\|cooling_device3:
	257	\|-----type: Fan
	258	\|-----max_state: 2
	259	\|-----cur_state: 0
e9ae7107 ZR	260
	261	/sys/class/hwmon:
	262
	263	\|hwmon0:
	264	\|-----name: acpitz
	265	\|-----temp1_input: 37000
	266	\|-----temp1_crit: 100000