tree aa5b2bea82a70c16291620a6c0bcd68e128d0141
parent bbbc01655243fecc83f8734f12a57e665b90ff9a
author Andrew Geissler <geissonator@yahoo.com> 1609880425 -0600
committer Andrew Geissler <geissonator@yahoo.com> 1609896766 -0600

host state transitioning support

The following commit has some relevant background:
https://github.com/openbmc/phosphor-dbus-interfaces/commit/9f65dfeaa5ab22cae03db45c9916868da9864f83

The new services introduced in this commit will set these new transition
states. They will work together with the existing state-manager
infrastructure in that the new services will set the transitions when
the targets start and the current software which looks for the targets
to complete will update the state to the official Running/Off.

But why not just have the existing software that monitors for the
targets to complete also monitor for them to start? This was a long and
dark hole I went down for a while. In the end, systemd D-Bus signals do
not provide enough information on target starts. The signals let you
know that "something" is going to happen to the target you're interested
in, but not the details. For example, if you start the
obmc-host-start@.target, you get two systemd notifications that indicate
"something" is going to happen to obmc-host-start@.target and also that
"something" is going to happen to obmc-host-stop@.target. This is
because when one target starts, it stops the other. Since they are both
just queued for "something" there's no mechanism to interrogate them for
which one is doing what. I tried a lot of different things here but
just couldn't get anything that covered all paths. The maintainers of
systemd have indicated on their mailing list that they are not
interested in enhancing the signal data because they feel like it would
be a rat hole of never ending data getting added to it.

Tested:
- Built into an image and verified CurrentHostState changed as expected
  doing a host on, off, and reboot.

Signed-off-by: Andrew Geissler <geissonator@yahoo.com>
Change-Id: Id2e9bd0394fc71944d26ce4bd40b136acf82b5e4