<html>

  <head>

    <meta http-equiv="content-type" content="text/html; charset=UTF-8">

  </head>

  <body text="#000000" bgcolor="#FFFFFF">

    <pre>Hi,

We have a need to know which sensor objects hosted by the various phosphor-hwmon

daemons belong to which inventory objects.  For example, we need to know that

the /xyz/openbmc_project/sensors/power/ps1_input_power sensor belongs to the

/xyz/openbmc_project/inventory/system/powersupply1 item.

To accomplish this, I am proposing we add a new environment variable to the

system specific phosphor-hwmon config files that the phosphor-hwmon code

can then use to create associations interfaces that will cause the mapper to

create the appropriate association D-Bus paths.

As an example, we could add to the power-supply1 conf file an ASSOCIATIONS

variable for each sensor (assuming ps1_input_power is represented by IN1):

    ASSOCIATIONS_IN1=/xyz/openbmc_project/inventory/system/powersupply1

The code would then see that and create a new org.openbmc.Associations interface

on the /xyz/openbmc_project/sensors/power/ps1_input_power path with an

associations property of:

    ["inventory",

     "sensors",

     "/xyz/openbmc_project/inventory/system/powersupply1"]

This leads to the mapper creating:

    /xyz/openbmc_project/sensors/power/ps1_input_power/inventory

With an xyz.openbmc_project.Association interface with an

endpoints property of:

    ["/xyz/openbmc_project/inventory/system/powersupply1"]

And also the other association path:

    /xyz/openbmc_project/inventory/system/powersupply1/sensors

With an xyz.openbmc_project.Association interface with an

endpoints property of:

    ["/xyz/openbmc_project/sensors/power/ps1_input_power"]

This now allows one to both find all sensors associated with a power supply, and

find which inventory item is associated with a particular sensor.  Note that

the endpoints property is an array, and can get entries from multiple places.

I suppose we could also put the forward/reverse association names, in this case

"inventory" and "sensors", into the hwmon config file, and also allow creating

multiple associations for each sensor if there is a usecase, though I would like

to keep it as simple as possible:

ASSOCIATIONS1_IN1=inventory,sensors,/xyz/openbmc_project/inventory/system/powersupply1

ASSOCIATIONS2_IN1=chassis,contained_sensors,/xyz/openbmc_project/inventory/system/chassis

What does everyone think?

Thanks

Matt</pre>

  </body>

</html>