tree dc00b37a95a47da18594120370a6b6e340bdb598
parent 4c549f63e1033b5ee47c54f1a80d060f15133b72
author Janet Adkins <janeta@us.ibm.com> 1732134860 -0600
committer Patrick Williams <patrick@stwcx.xyz> 1737997923 +0000

Add new interface to define sensor purpose

A chassis can have a sensor which tracks the total power consumption.
Clients such as bmcweb need a programmatic approach to finding the
unique sensor from the chassis.

A design discussion [1] in development channel of Discord settled on the
following approach:
 - Define a D-Bus interface for defining a special purpose for a
   sensor.
 - Use the existing all_sensors/chassis association to connect the
   sensor to its Chassis.
 - Clients such as bmcweb use object mapper to find all_sensors
   associated with the Chassis. They then filter to
   find the sensor implementing the specific purpose required.

This initial implementation only defines a single special purpose. The
expectation is others will be added as needed in the future.

The openpower-occ-control repo implemented a total_power association.[2]
This will be modified to implement this new interface on the total_power
sensor.

There is a commit for bmcweb which will be modified to use this new
approach for finding the total_power sensor.[3]

Note: There is technical debt to convert all_sensors/chassis
associations to use the monitoring/monitored_by association instead.[4]
That change would also need to convert the association used to find
objects implementing this interface.

[1] https://discord.com/channels/775381525260664832/867820390406422538/1326612654852280433
[2] https://gerrit.openbmc.org/c/openbmc/openpower-occ-control/+/75572
[3] https://gerrit.openbmc.org/c/openbmc/bmcweb/+/57717
[4] https://discord.com/channels/775381525260664832/867820390406422538/1326609419022372916

Change-Id: Ic8b509c9b2b17e823243f7b784ef941ec461cddb
Signed-off-by: Janet Adkins <janeta@us.ibm.com>