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Commit 38bb0849 authored by Frans Pop's avatar Frans Pop Committed by Len Brown
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thermal: sysfs-api.txt - reformat for improved readability 



The document currently uses large indentations which make the text
too wide for easy readability. Also improve general consistency.

Signed-off-by: default avatarFrans Pop <elendil@planet.nl>
Acked-by: default avatarZhang Rui <rui.zhang@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLen Brown <len.brown@intel.com>
parent 625120a4

Documentation/thermal/sysfs-api.txt

+192 −188
Original line number Diff line number Diff line 
Generic Thermal Sysfs driver How To

=========================

===================================



Written by Sujith Thomas <sujith.thomas@intel.com>, Zhang Rui <rui.zhang@intel.com>
@@ -10,20 +10,20 @@ 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.

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.

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.

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
@@ -31,12 +31,12 @@ and throttle appropriate devices. 
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)

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.

    /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.
@@ -46,8 +46,8 @@ and throttle appropriate devices. 
	.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

	    - "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.
@@ -57,16 +57,16 @@ and throttle appropriate devices. 
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.

    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.

    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.
@@ -77,15 +77,15 @@ and throttle appropriate devices. 
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.

    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 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
@@ -95,9 +95,9 @@ and throttle appropriate devices. 
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.

    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
@@ -114,153 +114,157 @@ 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

    |---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

    |---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.

Then next 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 successful execution of

thermal_zone_bind_cooling_device/thermal_zone_unbind_cooling_device.



/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

/sys/class/thermal/thermal_zone[0-*]:

    |---cdev[0-*]:		[0-*]th cooling device in 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.

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-*].

    |---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.

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)

	E.g: "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

	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.

	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.

	RW, Optional



trip_point_[0-*]_temp		The temperature above which trip point will be fired

trip_point_[0-*]_temp

	The temperature above which trip point will be fired.

	Unit: millidegree Celsius

				RO

				Optional

	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

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

cdev[0-*]

	Sysfs link to the thermal cooling device node where the sys I/F

	for cooling device throttling control represents.

				RO

				Optional

	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

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

*****************************



type

	String which represents the type of device, e.g:

	- for generic ACPI: should be "Fan", "Processor" or "LCD"

	- for memory controller device on intel_menlow platform:

	  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:

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]*/

    |---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

    |---type:			Processor

    |---max_state:		8

    |---cur_state:		0



|cooling_device3:

	|-----type:			Fan

	|-----max_state:		2

	|-----cur_state:		0

    |---type:			Fan

    |---max_state:		2

    |---cur_state:		0



/sys/class/hwmon:



|hwmon0:

	|-----name:			acpitz

	|-----temp1_input:		37000

	|-----temp1_crit:		100000
 
    |---name:			acpitz

    |---temp1_input:		37000

    |---temp1_crit:		100000