1# dbus-sensors 2 3dbus-sensors is a collection of sensor applications that provide the 4xyz.openbmc_project.Sensor collection of interfaces. They read sensor values 5from hwmon, d-bus, or direct driver access to provide readings. Some advance 6non-sensor features such as fan presence, pwm control, and automatic cpu 7detection (x86) are also supported. 8 9## key features 10 11- runtime re-configurable from d-bus (entity-manager or the like) 12 13- isolated: each sensor type is isolated into its own daemon, so a bug in one 14 sensor is unlikely to affect another, and single sensor modifications are 15 possible 16 17- async single-threaded: uses sdbusplus/asio bindings 18 19- multiple data inputs: hwmon, d-bus, direct driver access 20 21## dbus interfaces 22 23A typical dbus-sensors object support the following dbus interfaces: 24 25``` 26Path /xyz/openbmc_project/sensors/<type>/<sensor_name> 27 28Interfaces xyz.openbmc_project.Sensor.Value 29 xyz.openbmc_project.Sensor.Threshold.Critical 30 xyz.openbmc_project.Sensor.Threshold.Warning 31 xyz.openbmc_project.State.Decorator.Availability 32 xyz.openbmc_project.State.Decorator.OperationalStatus 33 xyz.openbmc_project.Association.Definitions 34 35``` 36 37Sensor interfaces collection are described 38[here](https://github.com/openbmc/phosphor-dbus-interfaces/tree/master/yaml/xyz/openbmc_project/Sensor). 39 40Consumer examples of these interfaces are 41[Redfish](https://github.com/openbmc/bmcweb/blob/master/redfish-core/lib/sensors.hpp), 42[Phosphor-Pid-Control](https://github.com/openbmc/phosphor-pid-control), 43[IPMI SDR](https://github.com/openbmc/phosphor-host-ipmid/blob/master/dbus-sdr/sensorcommands.cpp). 44 45## Reactor 46 47dbus-sensor daemons are [reactors](https://github.com/openbmc/entity-manager) 48that dynamically create and update sensors configuration when system 49configuration gets updated. 50 51Using asio timers and async calls, dbus-sensor daemons read sensor values and 52check thresholds periodically. PropertiesChanged signals will be broadcasted for 53other services to consume when value or threshold status change. OperationStatus 54is set to false if the sensor is determined to be faulty. 55 56A simple sensor example can be found 57[here](https://github.com/openbmc/entity-manager/blob/master/docs/my_first_sensors.md). 58 59## configuration 60 61Sensor devices are described using Exposes records in configuration file. Name 62and Type fields are required. Different sensor types have different fields. 63Refer to entity manager 64[schema](https://github.com/openbmc/entity-manager/blob/master/schemas/legacy.json) 65for complete list. 66 67## sensor documentation 68 69- [ExternalSensor](https://github.com/openbmc/docs/blob/master/designs/external-sensor.md) 70 virtual sensor 71