Generic Thermal Sysfs driver How To
-=========================
+===================================
Written by Sujith Thomas <sujith.thomas@intel.com>, Zhang Rui <rui.zhang@intel.com>
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
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.
+1.1.1 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.
+ 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.
+ 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.
+ 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);
+ 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.
+ 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);
+ 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.
+ 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
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.
- 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
+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
+
+*****************************
+* 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:
+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
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