On Wed, Jul 11, 2018 at 12:44:23PM +0200, Nicholas wrote:
> > > > Maybe a solution could be to have an env_save() function which
> > > > acts in a similar way as proposed in my patch and an
> > > > env_save_prio() function, which acts like the env_load()
> > > > i.e. looking for the best working location instead of relying
> > > > on what has been stored into gd-> env_load_location.
> > > 
> > > I don't really see a use-case for overriding wherever the
> > > environment at the user-level actually. At the board level, for
> > > redundancy or transition, yes, definitely, but we can already do
> > > that.
> >
> > Well, the use case I saw was that I wanted to test redundant
> > environment  storage. I admit this is not an end user use case but
> > a developer use  case, so I guess you're right.
> > 
> > So after fixing this endless loops I see two questions: - to which
> > environment do we store if the one in 'env_load_location'  fails
> > to store?
> Good question. My opinion is that it strongly depends on what we want
> to achieve with the implementation: do we want 1) to keep the
> consistency between load and save, or we want 2) to guarantee to be
> able to load/save from at least one location? 
> If 1) then a failure on env_save() simply fails and doesn't store
> anything. In other words we are multi-env when loading but single-env
> when storing. We are actually binding env_save() to the last
> env_load()'s result.
> If 2) then a failure on env_save() will try all the available locations
> but we are open to misalignments. Here we are full multi-env since
> env_save() and env_load() are not bound together.

In that case, we don't want to store to a lower priority, but to a
higher one. Otherwise, the environment will be saved just fine, but
will not be read next time, which will be very confusing to the user.

And with a higher priority, you might end up overwriting something you
weren't expecting to overwrite, so I'd vote 1.

Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering

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