entity manager configurations and dbus interfaces

[Ed Tanous]

On Thu, Sep 24, 2020 at 7:30 AM Brad Bishop <bradleyb at fuzziesquirrel.com> wrote:
>
> Hi Ed
>
> Will quote a comment from this EM review:
>
> https://gerrit.openbmc-project.xyz/36702
>
> > entity-manager was designed with the tenant that it config files have
> > no knowledge of dbus.
>
> FWIW I had no idea this was the case.
>
> > We've broken that a little with the inventory interfaces on the entity
> > as a short term patch to gain some compatibility, but its easy enough
> > to roll back in the future.
>
> Interesting - so there is a vision here, but I have no idea what it is.
> Can you elaborate on how you envision inventory working if EM is not
> implementing the inventory dbus interfaces?

In the simplest terms, one goal of entity-manager is for an engineer
unfamiliar with OpenBMC to be able to add support for a new component,
be it a baseboard, drive, or add in card, in less than a day.  Dbus
APIs take more than a day to learn, so we need to find a way to
provide a syntax that is self describing (and ideally well documented,
but that's another issue that I'm hoping to tackle soon) as well as
relatively isolated from the complexities of the OpenBMC core.

Another advantage of this is portability, if any wide sweeping
architecture changes happen (ex, we rewrite the core in rust or we
build a DBusless OpenBMC) we have a minimum definition of the things
that are unique about the pieces of hardware we support, and don't
have to re-engineer every piece of hardware that's in the list.


>
> thx - brad