System Firmware states on D-Bus

[Andrew Geissler]

I sent an email[1] out a while ago about mapping Redfish Host states to
PLDM Boot values.

Now that we have that design moving, the next question is whether we want
to try and map these to our current IPMI-based state sensors[2]
(OperatingSystemState and BootProgress)? These are currently displayed when
a user does a "obmcutil state" and I see a few other repositories reference
them for boot status. The openbmc-test suite also uses them fairly extensively
to verify different boot tests.

If we want to maintain backwards compatibility then we should map the new PLDM
based boot progress to these two. Mapping them does not seem too difficult.
I could have phosphor-host-state-manager (which hosts these D-Bus properties)
listen for changes to the PLDM property and update the two properties
appropriately. This assumes a system where the system firmware is only
IPMI or PLDM (not both) since they would not play all that well together.

From a Redfish API perspective, it will just directly look at the PLDM
property.

Thoughts?

[1]: https://lists.ozlabs.org/pipermail/openbmc/2020-February/020417.html
[2]: https://github.com/openbmc/phosphor-dbus-interfaces/blob/master/xyz/openbmc_project/State/Boot/Progress.interface.yaml
     https://github.com/openbmc/phosphor-dbus-interfaces/blob/master/xyz/openbmc_project/State/OperatingSystem/Status.interface.yaml