On Tue, 2013-02-05 at 16:16 +0530, Durgadoss R 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 <durgados...@intel.com> > --- > Documentation/thermal/sysfs-api2.txt | 247 > ++++++++++++++++++++++++++++++++++ > 1 file changed, 247 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..24e23f4 > --- /dev/null > +++ b/Documentation/thermal/sysfs-api2.txt > @@ -0,0 +1,247 @@ > +Thermal Framework > +----------------- > + > +Written by Durgadoss R <durgados...@intel.com> > +Copyright (c) 2012 Intel Corporation > + > +Created on: 4 November 2012 > +Updated on: 5 February 2013 > + > +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. > + > +The thermal sensor source file can be generic (can be any sensor driver, > +in any subsystem). This driver will use the sensor APIs and register with > +thermal framework to participate in platform Thermal management. This > +does not (and should not) know about which zone it belongs to, or any > +other information about platform thermals. A sensor driver is a standalone > +piece of code, which can optionally register with thermal framework. > + > +However, for any platform, there should be a platformX_thermal.c file, > +which will know about the platform thermal characteristics (like how many > +sensors, zones, cooling devices, etc.. And how they are related to each other > +i.e the mapping information). Only in this file, the zone level APIs should > +be used, in which case the file will have all information required to attach > +various sensors to a particular zone. > + > +This way, we can have one platform level thermal file, which can support > +multiple platforms (may be)using the same set of sensors (but)binded in > +a different way. This file can get the platform thermal information > +through Firmware, ACPI tables, device tree etc. > + > +Unfortunately, today we don't have many drivers that can be clearly > +differentiated as 'sensor_file.c' and 'platform_thermal_file.c'. > +But very soon we will need/have. The reason I am saying this is because > +we are seeing a lot of chip drivers, starting to use thermal framework, > +and we should keep it really light-weight for them to do so. > + > +An Example: drivers/hwmon/emc1403.c - a generic thermal chip driver > +In one platform this sensor can belong to 'ZoneA' and in another the > +same can belong to 'ZoneB'. But, emc1403.c does not really care about > +where does it belong. It just reports temperature. > + > +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 > + count: Number of programmable thresholds associated with this 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 > + .get_hyst: get hysteresis value associated with a threshold > + .set_hyst: set hysteresis value associated with a threshold > + > +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.
s/sensr/sensor > + > + 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/. > + 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. if this is true, actually it is, it breaks the sysfs "one value per file" rule. we should have multiple active/passive attributes if there are multiple trip points. thanks, rui > + > + 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/mapY_*. Each map attribute helps > + to describe 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/sensor[0-*]: > + |---type: Name of the thermal sensor > + |---temp_input: Current temperature in mC > + |---threshold[0-*]: Threshold temperature in mC > + |---threshold[0-*]_hyst:Optional hysteresis value in mC > + > +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 a sensor(Y) > + present in the thermal zone(X). All values are in mC. > + /sys/class/thermal/zoneX/: > + |---sensorY_trip_hot: hot trip point > + |---sensorY_trip_critical: critical trip point > + |---sensorY_trip_passive: passive trip point > + |---sensorY_trip_active: active trip point > + > +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/: > + |---mapY_trip_type: active/passive > + |---mapY_sensor_name: cpu > + |---mapY_cdev_name: proc > + |---mapY_trip_mask: 0x03 > + |---mapY_weights: 50 30 > + > + 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]. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
