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-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
-
-
-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-*]: [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.
-
-/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.
- 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.
- 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.
- 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
-
-passive
- Attribute is only present for zones in which the passive cooling
- policy is not supported by native thermal driver. Default is zero
- and can be set to a temperature (in millidegrees) to enable a
- passive trip point for the zone. Activation is done by polling with
- an interval of 1 second.
- Unit: millidegrees Celsius
- Valid values: 0 (disabled) or greater than 1000
- RW, Optional
-
-*****************************
-* Cooling device attributes *
-*****************************
-
-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:
-
-/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
-
-4. Event Notification
-
-The framework includes a simple notification mechanism, in the form of a
-netlink event. Netlink socket initialization is done during the _init_
-of the framework. Drivers which intend to use the notification mechanism
-just need to call thermal_generate_netlink_event() with two arguments viz
-(originator, event). Typically the originator will be an integer assigned
-to a thermal_zone_device when it registers itself with the framework. The
-event will be one of:{THERMAL_AUX0, THERMAL_AUX1, THERMAL_CRITICAL,
-THERMAL_DEV_FAULT}. Notification can be sent when the current temperature
-crosses any of the configured thresholds.