phosphor-pid-control handle missing input sensor

[Ren, Zhikui]

Hi All,

We use EntityManager and dbus-sensors to scan for installed hardware and sensors. Phosphor-pid-control is used to control fans by creating passive sensors that monitors the dbus-sensors objects.
We are looking at adding the ability to detect missing sensors due to some hardware failures and boost fans based on the zone config.
The challenges are

  1.  Correctly identify sensors that expected to be present, but are not discovered.

For example, not all CPUs are populated on a baseboard, so simply adding a "required" sensor for CPUs will not work.

A "required" sensor need to be tied into a present detection, which may or may not be supported by hardware.

  1.  Notify phosphor-pid-control of missing sensor and/or "stale" sensor at run time
This can be accomplished by dbus-sensors creating the missing sensor object and set it to failed state.
Fan control also needs to detect any sensor that stops updating its value and treat that as a failed sensor.

I am reaching out to the community to see if anyone has already addressed this issue or has some design that can be leveraged to solve the above issue.

Thanks,
Zhikui

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