[U-Boot] Default environment file

[Stefano Babic]

Hi Tom,

Hi everybody,

On 12/06/19 16:16, Tom Rini wrote:
> On Wed, Jun 12, 2019 at 10:43:26AM +0200, Stefano Babic wrote:
>> Hi Pascal,
>>
>> On 12/06/19 10:20, Linder Pascal wrote:
>>> Hi everyone,
>>>
>>>
>>> I am currently moving the configurations of the KM boards from header files to Kconfig. But for the customly defined environment variables I did not found a decent solution until I have come across the default environment file, which seems very interesting to me.
>>>
>>>
>>> To this day, nevertheless, it appears that noone made use of the CONFIG_USE_DEFAULT_ENV_FILE configuration defined in env/Kconfig. Does anyone still have an example for this kind of environment definition or knows how to create it?
>>>
>>>
>>> In my opinion, this could be highly relevant for the transition away from the header files in include/configs.
>>>
>>
>> Fully agree. Rather, I do not think there is a relevant example. But the
>> environment is something like data and should not be part of the header
>> file as it is for histoical reason. I added some times ago a way to
>> extract the environment from the header and make the transition easy
>> (see make u-boot-initial-env). And if the environment is split from the
>> header as CONFIG_USE_DEFAULT_ENV_FILE allows, it is also easier to set
>> an own environment via OE BSP layer without pushing for each small
>> change to U-Boot. Not only, environments often conflict, and what is
>> good for a project becomes evil for another one.
> 
> With the high-level goal of being able to eliminate the include/configs
> file, we need to figure out a better solution to dealing with the
> default environment. 

Right.

> Shuffling things into include/environment/ has
> been the first step I've tried but I'm absolutely not tied down to this
> and if people are motivated to push in a new solution to this overall
> problem I'm happy to see it happen.  This sounds like a good overall
> idea.

The default / initial environment is more a configuration data for the
bootloader as part of it. Linking it to the rest of code was done at the
beginning of U-Boot and it was never changed for historical reasons, but
the environment is just configuration data.  Theoretically, we could
have the same environment for multiple boards and we could use the same
files.

IMHO it should be more a job for binman as for the linker to put
environment and u-boot code together. My first idea could be to drop it
from code and appending it to the binary, letting the code (SPL /
u-boot) know where the initial environment is found.
CONFIG_USE_DEFAULT_ENV_FILE could be used to set which file should be
taken by binman - the result is still a single file that can be signed
in case of secure boot.

Best regards,
Stefano

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