Sensors, of course, are probably the most interesting part of IPMI. Really, everything else is there so the sensors may be known and monitored. Unfortunately, sensors are also the most complicated part of IPMI. OpenIPMI is really unable to hide a lot of this complexity, it is passed on to the user, so expect to have to do some reading and understanding.
IPMI defines two basic different types of sensors. Threshold sensors monitor “analog” things like tem- perature, voltage, or fan speed. Discrete sensors monitor events or states, like entity presence, software initialization progress, or if external power is applied to the system. Table 8.1 describes the basic types of sensors.
Table 8.1: Event/Reading Type Codes
Both threshold and discrete sensors may generate events. This is optional, the SDR for the sensor describes the sensor’s event support.
Some sensors support each individual bit or state being enabled or disabled. Others may only support events for the whole sensor being enabled or disabled. Still others may only support a global enable for the entire MC.
“Rearm” means setting the sensor so it will go off again. TBD - write this.
Threshold sensors report their readings in values from 0-255. OpenIPMI makes every effort to convert this to a floating-point value for you to use. IPMI defines standard ways to convert values using various