[Design] PSU firmware update

[Lei YU]

> I see it as having a single tarball file that has the required files to
> update the
> BMC and the PSU. When this tarball is uploaded, then a new Version with
> a Purpose
> of System or some other name is created. When this Version is activated,
> this
> triggers the BMC updater (existing) and the PSU updater (new) to check
> if all
> the necessary files to perform the update of their component exist. If
> yes, each
> updater updates their piece and if any one fails it'd mark the Version
> as Failed
> (TBD on synchronizing the updaters to mark the Version as Active or
> Failed).
> So the PSU would be updated at the same time as the BMC, but done by its
> own
> updater application.
>
> Thoughts?

A single tarball containing multiple images for multiple purposes is not
implemented yet.
So this design doc is expected not to cover that, is that OK?

As long as the PSU purpose is implemented correctly with the same interface,
it should not be difficult to support it in multiple purpose case.