By default, it monitors CPU temperature using available CPU digital temperature sensors and maintains CPU temperature under control, before HW takes aggressive correction action.
Thermal daemon looks for thermal sensors and thermal cooling drivers in the Linux thermal sysfs (/sys/class/thermal) and builds a list of sensors and cooling drivers. Each of the thermal sensors can optionally be binded to a cooling drivers by the in kernel drivers. In this case the Linux kernel thermal core can directly take actions based on the temperature trip points, for each sensor and associated cooling device. For example a trip temperature X in a sensor can be associates a cooling driver Y. So when the sensor temperature = X, the cooling driver "Y" is activated.
Thermal daemon allows one to change this relationship or add new one via a thermal configuration file (thermal-conf.xml). This file is automatically created (thermal-conf.xml.auto) and used, if the platform has ACPI thermal relationship table. If not this needs to be manually configured.
For manual configuration refer to the manual page of the thermal-conf.xml.
In some newer platforms the auto creation of the config file is done by a companion tool "dptfxtract". This tool can be downloaded from "https://github.com/intel/dptfxtract". It is suggested as parts of the install process, run dptfxtract.
There can be multiple configuration files. User can select a configuration file via -config-file option to overide the default selection. The default selection picks one of the file in the following order:
- /etc/thermald/thermal-conf.xml.auto
- /var/run/thermald/thermal-conf.xml.auto
- /etc/thermald/thermal-conf.xml
(*Assuming configure prefix=/ is used during build.)
There is another companion tool "ThermalMonitor", which presents a graphical front end. This allows the monitoring of sensors and changing of thermal trips to give the user more control. The source code of "ThermalMonitor" is a part of the thermald github source, in the tools folder.