dbus-sensors is a collection of sensor applications that provide the xyz.openbmc_project.Sensor collection of interfaces. They read sensor values from hwmon, d-bus, or direct driver access to provide readings. Some advance non-sensor features such as fan presence, pwm control, and automatic cpu detection (x86) are also supported.

• runtime re-configurable from d-bus (entity-manager or the like)

• isolated: each sensor type is isolated into its own daemon, so a bug in one sensor is unlikely to affect another, and single sensor modifications are possible

• async single-threaded: uses sdbusplus/asio bindings

• multiple data inputs: hwmon, d-bus, direct driver access

A typical dbus-sensors object support the following dbus interfaces:

Path        /xyz/openbmc_project/sensors/<type>/<sensor_name>

Interfaces  xyz.openbmc_project.Sensor.Value
            xyz.openbmc_project.Sensor.Threshold.Critical
            xyz.openbmc_project.Sensor.Threshold.Warning
            xyz.openbmc_project.State.Decorator.Availability
            xyz.openbmc_project.State.Decorator.OperationalStatus
            xyz.openbmc_project.Association.Definitions

Sensor interfaces collection are described here.

Consumer examples of these interfaces are Redfish, Phosphor-Pid-Control, IPMI SDR.

dbus-sensor daemons are reactors that dynamically create and update sensors configuration when system configuration gets updated.

Using asio timers and async calls, dbus-sensor daemons read sensor values and check thresholds periodically. PropertiesChanged signals will be broadcasted for other services to consume when value or threshold status change. OperationStatus is set to false if the sensor is determined to be faulty.

A simple sensor example can be found here.

Sensor devices are described using Exposes records in configuration file. Name and Type fields are required. Different sensor types have different fields. Refer to entity manager schema for complete list.

• ExternalSensor virtual sensor