[U-Boot] [RFC PATCH] u-boot: remove driver lookup loop from env_save()

[Simon Goldschmidt]

On 11.07.2018 15:50, Maxime Ripard wrote:
> 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.

I agree that 1 would be best. But from reading the code, unless I'm 
totally wrong, it seems that the patch sent by Nicholas does not suffice:

If no location contained a valid environment (e.g. no environment 
written yet), the lowest priority will be written as 
'gd->env_load_location' is set to the lowest priority from iterating 
locations in 'env_load()'.

So we might have to reset 'gd->env_load_location' to highest prio if 
loading the environment fails.


Simon