diff mbox

[RFC,6/7] Thermal: Add Documentation to new APIs

Message ID 1353149158-19102-7-git-send-email-durgadoss.r@intel.com (mailing list archive)
State Not Applicable, archived
Delegated to: Zhang Rui
Headers show

Commit Message

durgadoss.r@intel.com Nov. 17, 2012, 10:45 a.m. UTC
This patch adds Documentation for the new APIs
introduced in this patch set. The documentation
also has a model sysfs structure for reference.

Signed-off-by: Durgadoss R <durgadoss.r@intel.com>
---
 Documentation/thermal/sysfs-api2.txt |  213 ++++++++++++++++++++++++++++++++++
 1 file changed, 213 insertions(+)
 create mode 100644 Documentation/thermal/sysfs-api2.txt

Comments

Hongbo Zhang Dec. 3, 2012, 7:19 a.m. UTC | #1
On 17 November 2012 18:45, Durgadoss R <durgadoss.r@intel.com> wrote:
> This patch adds Documentation for the new APIs
> introduced in this patch set. The documentation
> also has a model sysfs structure for reference.
>
> Signed-off-by: Durgadoss R <durgadoss.r@intel.com>
> ---
>  Documentation/thermal/sysfs-api2.txt |  213 ++++++++++++++++++++++++++++++++++
>  1 file changed, 213 insertions(+)
>  create mode 100644 Documentation/thermal/sysfs-api2.txt
>
> diff --git a/Documentation/thermal/sysfs-api2.txt b/Documentation/thermal/sysfs-api2.txt
> new file mode 100644
> index 0000000..be67125
> --- /dev/null
> +++ b/Documentation/thermal/sysfs-api2.txt
> @@ -0,0 +1,213 @@
> +Thermal Framework
> +-----------------
> +
> +Written by Durgadoss R <durgadoss.r@intel.com>
> +Copyright (c) 2012 Intel Corporation
> +
> +Created on: 4 November 2012
> +
> +0. Introduction
> +---------------
> +The Linux thermal framework provides a set of interfaces for thermal
> +sensors and thermal cooling devices (fan, processor...) to register
> +with the thermal management solution and to be a part of it.
> +
> +This document focuses on how to enable new thermal sensors and cooling
> +devices to participate in thermal management. This solution is intended
> +to be 'light-weight' and platform/architecture independent. Any thermal
> +sensor/cooling device should be able to use the infrastructure easily.
> +
> +The goal of thermal framework is to expose the thermal sensor/zone and
> +cooling device attributes in a consistent way. This will help the
> +thermal governors to make use of the information to manage platform
> +thermals efficiently.
> +
> +1. Terminology
> +--------------
> +This section describes the terminology used in the rest of this
> +document as well as the thermal framework code.
> +
> +thermal_sensor: Hardware that can report temperature of a particular
> +               spot in the platform, where it is placed. The temperature
> +               reported by the sensor is the 'real' temperature reported
> +               by the hardware.
> +thermal_zone:  A virtual area on the device, that gets heated up. It may
> +               have one or more thermal sensors attached to it.
> +cooling_device:        Any component that can help in reducing the temperature of
> +               a 'hot spot' either by reducing its performance (passive
> +               cooling) or by other means(Active cooling E.g. Fan)
> +
> +trip_points:   Various temperature levels for each sensor. As of now, we
> +               have four levels namely active, passive, hot and critical.
> +               Hot and critical trip point support only one value whereas
> +               active and passive can have any number of values. These
> +               temperature values can come from platform data, and are
> +               exposed through sysfs in a consistent manner. Stand-alone
> +               thermal sensor drivers are not expected to know these values.
> +               These values are RO.
> +thresholds:    These are programmable temperature limits, on reaching which
> +               the thermal sensor generates an interrupt. The framework is
> +               notified about this interrupt to take appropriate action.
> +               There can be as many number of thresholds as that of the
> +               hardware supports. These values are RW.
> +
> +thermal_map:   This provides the mapping (aka binding) information between
> +               various sensors and cooling devices in a particular zone.
> +               Typically, this also comes from platform data; Stand-alone
> +               sensor drivers or cooling device drivers are not expected
> +               to know these mapping information.
> +
> +2. Thermal framework APIs
> +-------------------------
> +2.1: For Thermal Sensors
> +2.1.1 thermal_sensor_register:
> +       This function creates a new sensor directory under /sys/class/thermal/
> +       as sensor[0-*]. This API is expected to be called by thermal sensor
> +       drivers. These drivers may or may not be in thermal subsystem. This
> +       function returns a thermal_sensor structure on success and appropriate
> +       error on failure.
> +
> +       name: Name of the sensor
> +       devdata: Device private data
> +       ops: Thermal sensor callbacks
> +               .get_temp: obtain the current temperature of the sensor
> +               .get_trend: obtain the trend of the sensor
> +               .get_threshold: get a particular threshold temperature
> +               .set_threshold: set a particular threshold temperature
> +
> +2.1.2 thermal_sensor_unregister:
> +       This function deletes the sensor directory under /sys/class/thermal/
> +       for the given sensor. Thermal sensor drivers may call this API
> +       during the driver's 'exit' routine.
> +
> +       ts: Thermal sensor that has to be unregistered
> +
> +2.1.3 enable_sensor_thresholds:
> +       This function creates 'threshold[0-*]' attributes under a particular
> +       sensorX directory. These values are RW. This function is called by
> +       the sensr driver only if the sensor supports interrupt mechanism.
> +
> +       ts: Thermal sensor for which thresholds have to be enabled
> +       num_thresholds: Number of thresholds supported by the sensor
> +
> +2.2: For Cooling Devices
> +2.2.1 thermal_cooling_device_register:
> +       This function adds a new thermal cooling device (fan/processor/...)
> +       to /sys/class/thermal/ folder as cooling_device[0-*]. This function
> +       is expected to be called by cooling device drivers that may be
> +       present in other subsystems also.
> +
> +       name: the cooling device name
> +       devdata: device private data
> +       ops: thermal cooling devices callbacks
> +       .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
> +
> +2.2.2 thermal_cooling_device_unregister:
> +       This function deletes the given cdev entry form /sys/class/thermal;
> +       and also cleans all the symlinks referred from various zones.
> +
> +       cdev: Cooling device to be unregistered
> +
> +2.3: For Thermal Zones
> +2.3.1 create_thermal_zone:
> +       This function adds a new 'zone' under /sys/class/thermal/
> +       directory as zone[0-*]. This zone has at least one thermal
> +       sensor and at most MAX_SENSORS_PER_ZONE number of sensors
> +       attached to it. Similarly, this zone has at least one cdev
> +       and at most MAX_CDEVS_PER_ZONE number of cdevs attached to it.
> +       Both the MAX_*_PER_ZONE values are configurable, through
> +       Kconfig option(during 'menuconfig').
> +
> +       name: Name of the thermal zone
> +       devdata: Device private data
> +
> +2.3.2 add_sensor_to_zone
> +       This function adds a 'sensorX' entry under /sys/class/thermal/
> +       zoneY/ directory. This 'sensorX' is a symlink to the actual
> +       sensor entry under /sys/class/thermal/. Correspondingly, the
> +       method remove_sensor_from_zone deletes the symlink.
> +
> +       tz: thermal zone structure
> +       ts: thermal sensor structure
> +
> +2.3.3 add_cdev_to_zone
> +       This function adds a 'cdevX' entry under /sys/class/thermal/
> +       zoneY/ directory. This 'cdevX' is a symlink to the actual
> +       cdev entry under /sys/class/thermal/. Correspondingly, the
> +       method remove_cdev_from_zone deletes the symlink.
> +
> +       tz: thermal zone structure
> +       cdev: thermal cooling device structure
> +
> +2.4 For Thermal Trip
> +2.4.1 add_sensor_trip_info
> +       This function adds trip point information for the given sensor,
> +       (under a given zone) under /sys/class/thermal/zoneX/thermal_trip/
> +       This API creates 4 sysfs attributes namely active, passive, hot,
> +       and critical. Each of these hold one or more trip point temperature
> +       values, as provided from platform data.
> +
> +       tz: thermal zone structure
> +       ts: thermal sensor to which the trip points are attached
> +       trip: trip point structure. Usually obtained from platform data
> +
> +2.5 For Thermal Map
> +2.5.1 add_map_entry
> +       This function adds a 'map[0-*]' sysfs attribute under
> +       /sys/class/thermal/zoneX/thermal_map/. Each map holds a space
> +       separated list of values, that specify the binding relationship
> +       between a sensor and a cdev in the given zone. The map structure
> +       is typically obtained as platform data. For example, through
> +       ACPI tables, SFI tables, Device tree etc.
> +
> +       tz: thermal zone to which a 'map' is being added
> +       map: thermal_map structure
> +
> +3. Sysfs attributes structure
> +-----------------------------
> +Thermal sysfs attributes will be represented under /sys/class/thermal.
> +
> +3.1: For Thermal Sensors
> +       /sys/class/thermal/thermal_zone[0-*]:
Should be /sys/class/thermal/sensor[0-*] ?

> +               |---type:               Name of the thermal sensor
> +               |---temp_input:         Current temperature in mC
> +               |---threshold[0-*]:     Threshold temperature
> +
> +3.2: For Thermal Cooling Devices
> +       /sys/class/thermal/cooling_device[0-*]:
> +               |---type:               Type of the cooling device
> +               |---max_state:          Maximum throttle state of the cdev
> +               |---cur_state:          Current throttle state of the cdev
> +
> +3.3: For Thermal Zones
> +       /sys/class/thermal/zone[0-*]:
> +               |---name:               Name of the thermal
> +               |---sensorX:            Symlink to ../sensorX
> +               |---cdevY:              Symlink to ../cdevY
> +               |---thermal_trip:       trip point values for sensors
> +               |---thermal_map:        mapping info between sensors and cdevs
> +
> +3.4: For Thermal Trip
> +       This attribute represents the trip point values for all sensors
> +       present in the thermal zone. All values are in mC.
> +       /sys/class/thermal/zoneX/thermal_trip/sensorY:
> +               |---hot:                hot trip point value
> +               |---critical:           critical trip point value
> +               |---passive:            list of passive trip point values
> +               |---active:             list of active trip point values
> +
> +3.5: For Thermal Map
> +       Each attribute represents the mapping/binding information between
> +       a sensor and a cdev, together with a trip type.
> +       /sys/class/thermal/zoneX/thermal_map/:
> +               |---mapX:               mapping information
> +       A typical map entry is like below:
> +
> +       trip_type  sensor  cdev  trip_mask  weight(s)
> +       passive    cpu     proc  0x03       50 30
> +       active     cpu     fan0  0x03       50 70
> +
> +       The trip mask is a bit string; if 'n' th bit is set, then for
> +       trip point 'n' this cdev is throttled with the given weight[n].
> --
> 1.7.9.5
>
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durgadoss.r@intel.com Dec. 3, 2012, 7:44 a.m. UTC | #2
Yes, it's a typo.
Will fix it in the next submission.

Thanks,
Durga

> -----Original Message-----
> From: Hongbo Zhang [mailto:hongbo.zhang@linaro.org]
> Sent: Monday, December 03, 2012 12:50 PM
> To: R, Durgadoss
> Cc: Zhang, Rui; linux-pm@vger.kernel.org; wni@nvidia.com;
> eduardo.valentin@ti.com; amit.kachhap@linaro.org;
> sachin.kamat@linaro.org
> Subject: Re: [RFC PATCH 6/7] Thermal: Add Documentation to new APIs
> 
> On 17 November 2012 18:45, Durgadoss R <durgadoss.r@intel.com> wrote:
> > This patch adds Documentation for the new APIs
> > introduced in this patch set. The documentation
> > also has a model sysfs structure for reference.
> >
> > Signed-off-by: Durgadoss R <durgadoss.r@intel.com>
> > ---
> >  Documentation/thermal/sysfs-api2.txt |  213
> ++++++++++++++++++++++++++++++++++
> >  1 file changed, 213 insertions(+)
> >  create mode 100644 Documentation/thermal/sysfs-api2.txt
> >
> > diff --git a/Documentation/thermal/sysfs-api2.txt
> b/Documentation/thermal/sysfs-api2.txt
> > new file mode 100644
> > index 0000000..be67125
> > --- /dev/null
> > +++ b/Documentation/thermal/sysfs-api2.txt
> > @@ -0,0 +1,213 @@
> > +Thermal Framework
> > +-----------------
> > +
> > +Written by Durgadoss R <durgadoss.r@intel.com>
> > +Copyright (c) 2012 Intel Corporation
> > +
> > +Created on: 4 November 2012
> > +
> > +0. Introduction
> > +---------------
> > +The Linux thermal framework provides a set of interfaces for thermal
> > +sensors and thermal cooling devices (fan, processor...) to register
> > +with the thermal management solution and to be a part of it.
> > +
> > +This document focuses on how to enable new thermal sensors and
> cooling
> > +devices to participate in thermal management. This solution is intended
> > +to be 'light-weight' and platform/architecture independent. Any thermal
> > +sensor/cooling device should be able to use the infrastructure easily.
> > +
> > +The goal of thermal framework is to expose the thermal sensor/zone and
> > +cooling device attributes in a consistent way. This will help the
> > +thermal governors to make use of the information to manage platform
> > +thermals efficiently.
> > +
> > +1. Terminology
> > +--------------
> > +This section describes the terminology used in the rest of this
> > +document as well as the thermal framework code.
> > +
> > +thermal_sensor: Hardware that can report temperature of a particular
> > +               spot in the platform, where it is placed. The temperature
> > +               reported by the sensor is the 'real' temperature reported
> > +               by the hardware.
> > +thermal_zone:  A virtual area on the device, that gets heated up. It may
> > +               have one or more thermal sensors attached to it.
> > +cooling_device:        Any component that can help in reducing the
> temperature of
> > +               a 'hot spot' either by reducing its performance (passive
> > +               cooling) or by other means(Active cooling E.g. Fan)
> > +
> > +trip_points:   Various temperature levels for each sensor. As of now, we
> > +               have four levels namely active, passive, hot and critical.
> > +               Hot and critical trip point support only one value whereas
> > +               active and passive can have any number of values. These
> > +               temperature values can come from platform data, and are
> > +               exposed through sysfs in a consistent manner. Stand-alone
> > +               thermal sensor drivers are not expected to know these values.
> > +               These values are RO.
> > +thresholds:    These are programmable temperature limits, on reaching
> which
> > +               the thermal sensor generates an interrupt. The framework is
> > +               notified about this interrupt to take appropriate action.
> > +               There can be as many number of thresholds as that of the
> > +               hardware supports. These values are RW.
> > +
> > +thermal_map:   This provides the mapping (aka binding) information
> between
> > +               various sensors and cooling devices in a particular zone.
> > +               Typically, this also comes from platform data; Stand-alone
> > +               sensor drivers or cooling device drivers are not expected
> > +               to know these mapping information.
> > +
> > +2. Thermal framework APIs
> > +-------------------------
> > +2.1: For Thermal Sensors
> > +2.1.1 thermal_sensor_register:
> > +       This function creates a new sensor directory under /sys/class/thermal/
> > +       as sensor[0-*]. This API is expected to be called by thermal sensor
> > +       drivers. These drivers may or may not be in thermal subsystem. This
> > +       function returns a thermal_sensor structure on success and
> appropriate
> > +       error on failure.
> > +
> > +       name: Name of the sensor
> > +       devdata: Device private data
> > +       ops: Thermal sensor callbacks
> > +               .get_temp: obtain the current temperature of the sensor
> > +               .get_trend: obtain the trend of the sensor
> > +               .get_threshold: get a particular threshold temperature
> > +               .set_threshold: set a particular threshold temperature
> > +
> > +2.1.2 thermal_sensor_unregister:
> > +       This function deletes the sensor directory under /sys/class/thermal/
> > +       for the given sensor. Thermal sensor drivers may call this API
> > +       during the driver's 'exit' routine.
> > +
> > +       ts: Thermal sensor that has to be unregistered
> > +
> > +2.1.3 enable_sensor_thresholds:
> > +       This function creates 'threshold[0-*]' attributes under a particular
> > +       sensorX directory. These values are RW. This function is called by
> > +       the sensr driver only if the sensor supports interrupt mechanism.
> > +
> > +       ts: Thermal sensor for which thresholds have to be enabled
> > +       num_thresholds: Number of thresholds supported by the sensor
> > +
> > +2.2: For Cooling Devices
> > +2.2.1 thermal_cooling_device_register:
> > +       This function adds a new thermal cooling device (fan/processor/...)
> > +       to /sys/class/thermal/ folder as cooling_device[0-*]. This function
> > +       is expected to be called by cooling device drivers that may be
> > +       present in other subsystems also.
> > +
> > +       name: the cooling device name
> > +       devdata: device private data
> > +       ops: thermal cooling devices callbacks
> > +       .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
> > +
> > +2.2.2 thermal_cooling_device_unregister:
> > +       This function deletes the given cdev entry form /sys/class/thermal;
> > +       and also cleans all the symlinks referred from various zones.
> > +
> > +       cdev: Cooling device to be unregistered
> > +
> > +2.3: For Thermal Zones
> > +2.3.1 create_thermal_zone:
> > +       This function adds a new 'zone' under /sys/class/thermal/
> > +       directory as zone[0-*]. This zone has at least one thermal
> > +       sensor and at most MAX_SENSORS_PER_ZONE number of sensors
> > +       attached to it. Similarly, this zone has at least one cdev
> > +       and at most MAX_CDEVS_PER_ZONE number of cdevs attached to it.
> > +       Both the MAX_*_PER_ZONE values are configurable, through
> > +       Kconfig option(during 'menuconfig').
> > +
> > +       name: Name of the thermal zone
> > +       devdata: Device private data
> > +
> > +2.3.2 add_sensor_to_zone
> > +       This function adds a 'sensorX' entry under /sys/class/thermal/
> > +       zoneY/ directory. This 'sensorX' is a symlink to the actual
> > +       sensor entry under /sys/class/thermal/. Correspondingly, the
> > +       method remove_sensor_from_zone deletes the symlink.
> > +
> > +       tz: thermal zone structure
> > +       ts: thermal sensor structure
> > +
> > +2.3.3 add_cdev_to_zone
> > +       This function adds a 'cdevX' entry under /sys/class/thermal/
> > +       zoneY/ directory. This 'cdevX' is a symlink to the actual
> > +       cdev entry under /sys/class/thermal/. Correspondingly, the
> > +       method remove_cdev_from_zone deletes the symlink.
> > +
> > +       tz: thermal zone structure
> > +       cdev: thermal cooling device structure
> > +
> > +2.4 For Thermal Trip
> > +2.4.1 add_sensor_trip_info
> > +       This function adds trip point information for the given sensor,
> > +       (under a given zone) under /sys/class/thermal/zoneX/thermal_trip/
> > +       This API creates 4 sysfs attributes namely active, passive, hot,
> > +       and critical. Each of these hold one or more trip point temperature
> > +       values, as provided from platform data.
> > +
> > +       tz: thermal zone structure
> > +       ts: thermal sensor to which the trip points are attached
> > +       trip: trip point structure. Usually obtained from platform data
> > +
> > +2.5 For Thermal Map
> > +2.5.1 add_map_entry
> > +       This function adds a 'map[0-*]' sysfs attribute under
> > +       /sys/class/thermal/zoneX/thermal_map/. Each map holds a space
> > +       separated list of values, that specify the binding relationship
> > +       between a sensor and a cdev in the given zone. The map structure
> > +       is typically obtained as platform data. For example, through
> > +       ACPI tables, SFI tables, Device tree etc.
> > +
> > +       tz: thermal zone to which a 'map' is being added
> > +       map: thermal_map structure
> > +
> > +3. Sysfs attributes structure
> > +-----------------------------
> > +Thermal sysfs attributes will be represented under /sys/class/thermal.
> > +
> > +3.1: For Thermal Sensors
> > +       /sys/class/thermal/thermal_zone[0-*]:
> Should be /sys/class/thermal/sensor[0-*] ?
> 
> > +               |---type:               Name of the thermal sensor
> > +               |---temp_input:         Current temperature in mC
> > +               |---threshold[0-*]:     Threshold temperature
> > +
> > +3.2: For Thermal Cooling Devices
> > +       /sys/class/thermal/cooling_device[0-*]:
> > +               |---type:               Type of the cooling device
> > +               |---max_state:          Maximum throttle state of the cdev
> > +               |---cur_state:          Current throttle state of the cdev
> > +
> > +3.3: For Thermal Zones
> > +       /sys/class/thermal/zone[0-*]:
> > +               |---name:               Name of the thermal
> > +               |---sensorX:            Symlink to ../sensorX
> > +               |---cdevY:              Symlink to ../cdevY
> > +               |---thermal_trip:       trip point values for sensors
> > +               |---thermal_map:        mapping info between sensors and cdevs
> > +
> > +3.4: For Thermal Trip
> > +       This attribute represents the trip point values for all sensors
> > +       present in the thermal zone. All values are in mC.
> > +       /sys/class/thermal/zoneX/thermal_trip/sensorY:
> > +               |---hot:                hot trip point value
> > +               |---critical:           critical trip point value
> > +               |---passive:            list of passive trip point values
> > +               |---active:             list of active trip point values
> > +
> > +3.5: For Thermal Map
> > +       Each attribute represents the mapping/binding information between
> > +       a sensor and a cdev, together with a trip type.
> > +       /sys/class/thermal/zoneX/thermal_map/:
> > +               |---mapX:               mapping information
> > +       A typical map entry is like below:
> > +
> > +       trip_type  sensor  cdev  trip_mask  weight(s)
> > +       passive    cpu     proc  0x03       50 30
> > +       active     cpu     fan0  0x03       50 70
> > +
> > +       The trip mask is a bit string; if 'n' th bit is set, then for
> > +       trip point 'n' this cdev is throttled with the given weight[n].
> > --
> > 1.7.9.5
> >
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diff mbox

Patch

diff --git a/Documentation/thermal/sysfs-api2.txt b/Documentation/thermal/sysfs-api2.txt
new file mode 100644
index 0000000..be67125
--- /dev/null
+++ b/Documentation/thermal/sysfs-api2.txt
@@ -0,0 +1,213 @@ 
+Thermal Framework
+-----------------
+
+Written by Durgadoss R <durgadoss.r@intel.com>
+Copyright (c) 2012 Intel Corporation
+
+Created on: 4 November 2012
+
+0. Introduction
+---------------
+The Linux thermal framework provides a set of interfaces for thermal
+sensors and thermal cooling devices (fan, processor...) to register
+with the thermal management solution and to be a part of it.
+
+This document focuses on how to enable new thermal sensors and cooling
+devices to participate in thermal management. This solution is intended
+to be 'light-weight' and platform/architecture independent. Any thermal
+sensor/cooling device should be able to use the infrastructure easily.
+
+The goal of thermal framework is to expose the thermal sensor/zone and
+cooling device attributes in a consistent way. This will help the
+thermal governors to make use of the information to manage platform
+thermals efficiently.
+
+1. Terminology
+--------------
+This section describes the terminology used in the rest of this
+document as well as the thermal framework code.
+
+thermal_sensor: Hardware that can report temperature of a particular
+		spot in the platform, where it is placed. The temperature
+		reported by the sensor is the 'real' temperature reported
+		by the hardware.
+thermal_zone:	A virtual area on the device, that gets heated up. It may
+		have one or more thermal sensors attached to it.
+cooling_device:	Any component that can help in reducing the temperature of
+		a 'hot spot' either by reducing its performance (passive
+		cooling) or by other means(Active cooling E.g. Fan)
+
+trip_points:	Various temperature levels for each sensor. As of now, we
+		have four levels namely active, passive, hot and critical.
+		Hot and critical trip point support only one value whereas
+		active and passive can have any number of values. These
+		temperature values can come from platform data, and are
+		exposed through sysfs in a consistent manner. Stand-alone
+		thermal sensor drivers are not expected to know these values.
+		These values are RO.
+thresholds:	These are programmable temperature limits, on reaching which
+		the thermal sensor generates an interrupt. The framework is
+		notified about this interrupt to take appropriate action.
+		There can be as many number of thresholds as that of the
+		hardware supports. These values are RW.
+
+thermal_map:	This provides the mapping (aka binding) information between
+		various sensors and cooling devices in a particular zone.
+		Typically, this also comes from platform data; Stand-alone
+		sensor drivers or cooling device drivers are not expected
+		to know these mapping information.
+
+2. Thermal framework APIs
+-------------------------
+2.1: For Thermal Sensors
+2.1.1 thermal_sensor_register:
+	This function creates a new sensor directory under /sys/class/thermal/
+	as sensor[0-*]. This API is expected to be called by thermal sensor
+	drivers. These drivers may or may not be in thermal subsystem. This
+	function returns a thermal_sensor structure on success and appropriate
+	error on failure.
+
+	name: Name of the sensor
+	devdata: Device private data
+	ops: Thermal sensor callbacks
+		.get_temp: obtain the current temperature of the sensor
+		.get_trend: obtain the trend of the sensor
+		.get_threshold: get a particular threshold temperature
+		.set_threshold: set a particular threshold temperature
+
+2.1.2 thermal_sensor_unregister:
+	This function deletes the sensor directory under /sys/class/thermal/
+	for the given sensor. Thermal sensor drivers may call this API
+	during the driver's 'exit' routine.
+
+	ts: Thermal sensor that has to be unregistered
+
+2.1.3 enable_sensor_thresholds:
+	This function creates 'threshold[0-*]' attributes under a particular
+	sensorX directory. These values are RW. This function is called by
+	the sensr driver only if the sensor supports interrupt mechanism.
+
+	ts: Thermal sensor for which thresholds have to be enabled
+	num_thresholds: Number of thresholds supported by the sensor
+
+2.2: For Cooling Devices
+2.2.1 thermal_cooling_device_register:
+	This function adds a new thermal cooling device (fan/processor/...)
+	to /sys/class/thermal/ folder as cooling_device[0-*]. This function
+	is expected to be called by cooling device drivers that may be
+	present in other subsystems also.
+
+	name: the cooling device name
+	devdata: device private data
+	ops: thermal cooling devices callbacks
+	.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
+
+2.2.2 thermal_cooling_device_unregister:
+	This function deletes the given cdev entry form /sys/class/thermal;
+	and also cleans all the symlinks referred from various zones.
+
+	cdev: Cooling device to be unregistered
+
+2.3: For Thermal Zones
+2.3.1 create_thermal_zone:
+	This function adds a new 'zone' under /sys/class/thermal/
+	directory as zone[0-*]. This zone has at least one thermal
+	sensor and at most MAX_SENSORS_PER_ZONE number of sensors
+	attached to it. Similarly, this zone has at least one cdev
+	and at most MAX_CDEVS_PER_ZONE number of cdevs attached to it.
+	Both the MAX_*_PER_ZONE values are configurable, through
+	Kconfig option(during 'menuconfig').
+
+	name: Name of the thermal zone
+	devdata: Device private data
+
+2.3.2 add_sensor_to_zone
+	This function adds a 'sensorX' entry under /sys/class/thermal/
+	zoneY/ directory. This 'sensorX' is a symlink to the actual
+	sensor entry under /sys/class/thermal/. Correspondingly, the
+	method remove_sensor_from_zone deletes the symlink.
+
+	tz: thermal zone structure
+	ts: thermal sensor structure
+
+2.3.3 add_cdev_to_zone
+	This function adds a 'cdevX' entry under /sys/class/thermal/
+	zoneY/ directory. This 'cdevX' is a symlink to the actual
+	cdev entry under /sys/class/thermal/. Correspondingly, the
+	method remove_cdev_from_zone deletes the symlink.
+
+	tz: thermal zone structure
+	cdev: thermal cooling device structure
+
+2.4 For Thermal Trip
+2.4.1 add_sensor_trip_info
+	This function adds trip point information for the given sensor,
+	(under a given zone) under /sys/class/thermal/zoneX/thermal_trip/
+	This API creates 4 sysfs attributes namely active, passive, hot,
+	and critical. Each of these hold one or more trip point temperature
+	values, as provided from platform data.
+
+	tz: thermal zone structure
+	ts: thermal sensor to which the trip points are attached
+	trip: trip point structure. Usually obtained from platform data
+
+2.5 For Thermal Map
+2.5.1 add_map_entry
+	This function adds a 'map[0-*]' sysfs attribute under
+	/sys/class/thermal/zoneX/thermal_map/. Each map holds a space
+	separated list of values, that specify the binding relationship
+	between a sensor and a cdev in the given zone. The map structure
+	is typically obtained as platform data. For example, through
+	ACPI tables, SFI tables, Device tree etc.
+
+	tz: thermal zone to which a 'map' is being added
+	map: thermal_map structure
+
+3. Sysfs attributes structure
+-----------------------------
+Thermal sysfs attributes will be represented under /sys/class/thermal.
+
+3.1: For Thermal Sensors
+	/sys/class/thermal/thermal_zone[0-*]:
+		|---type:		Name of the thermal sensor
+		|---temp_input:		Current temperature in mC
+		|---threshold[0-*]:	Threshold temperature
+
+3.2: For Thermal Cooling Devices
+	/sys/class/thermal/cooling_device[0-*]:
+		|---type:		Type of the cooling device
+		|---max_state:		Maximum throttle state of the cdev
+		|---cur_state:		Current throttle state of the cdev
+
+3.3: For Thermal Zones
+	/sys/class/thermal/zone[0-*]:
+		|---name:		Name of the thermal
+		|---sensorX:		Symlink to ../sensorX
+		|---cdevY:		Symlink to ../cdevY
+		|---thermal_trip:	trip point values for sensors
+		|---thermal_map:	mapping info between sensors and cdevs
+
+3.4: For Thermal Trip
+	This attribute represents the trip point values for all sensors
+	present in the thermal zone. All values are in mC.
+	/sys/class/thermal/zoneX/thermal_trip/sensorY:
+		|---hot:		hot trip point value
+		|---critical:		critical trip point value
+		|---passive:		list of passive trip point values
+		|---active:		list of active trip point values
+
+3.5: For Thermal Map
+	Each attribute represents the mapping/binding information between
+	a sensor and a cdev, together with a trip type.
+	/sys/class/thermal/zoneX/thermal_map/:
+		|---mapX:		mapping information
+	A typical map entry is like below:
+
+	trip_type  sensor  cdev  trip_mask  weight(s)
+	passive    cpu     proc  0x03       50 30
+	active     cpu     fan0  0x03       50 70
+
+	The trip mask is a bit string; if 'n' th bit is set, then for
+	trip point 'n' this cdev is throttled with the given weight[n].