[Design] PSU firmware update

[Lei YU]

> > And during updating:
> > 4. After the update is done on a PSU, the AC input and DC standby output shall
> > be checked.
>
> What happens if this fail? Auto roll back or just an error log?

I do not think there will be a way to roll back (and it could get failure on
rolling back as well).
So probably just log an error and do not update other PSUs, so that the
system's other PSUs are good.

> > The PSU firmware code update will re-use the current interfaces to upload,
> > verify, and activate the image.
>
> Yes, this ensures the existing Redfish firmware update API's implemented
> within bmcweb will also work for this without any changes required.

Yup.

> >    * When the PSU code update is completed, an informational event log shall be
> >      created.
> Is this a normal requirement when it comes to PSU's? We don't do this for BMC
> or PNOR.

I expect that an informational log is good to tell that something is done,
something like audit log.
But we could remove this requirement if it is not mandatory.