Re: [PATCH v5 3/5] env: Allow U-Boot scripts to be placed in a .env file

Wolfgang Denk
2021-10-06T07:08:41Z

Dear Simon,

In message <CAPnjgZ3WVvso8uSeKyiOg6oR_R=nkguGZYXGb9Ws-s5dmO5GmQ@mail.gmail.com> you wrote:
>
> > 1) This requires that the .env files are run through CPP, which is
> > only added in a later patch.
>
> OK perhaps I should just merge the patches. It is a bit artificial
> having two and it seems that people agree we need the += syntax.

Yes, some way to append to the environment is useful, and using '+='
is an intuitive syntax for it. I'm just not happy about sneeking in
a new, undocumented restriction on U-Boot variable names. Yes,
there are probably not many systems around (if any) where a variable
name ends in a plus sign, but we should be consistent.

I have to admit that I don't have any nice alternative suggestion.
If we stick with the rule that only NUL and '=' cannot be used in a
variable name, we could write

variable=+value

instead. But this does not look as nice as '+=', and we need an
escape mechanism for the case where we want a simple assignment of a
value that starts with a '+'.

BTW: If we would add such a feature to U-Boot (which seems to be no
bad idea to me) we would probably implement an "env append" command?

> > 2) Even if I add an "#include board/<vendor>/env/common.env" in my
> > <board>.env files, your logic would trigger on the existence of
> > the common.env file and ignore the <board>.env files.
>
> OK, so I if reverse that, are you happy? What do you think about my
> explanation above?

The longer I think about it the more I wonder if any hard coded file
names are really a good way to handle this. For example there might
be the case where we have 4 boards A, B, C and D, and boards A and B
would use one env file, and C and D would use another. this does
not match the "<board>.env" scheme, and "common.env" does not fit
either, as we have two "common" files.

I wonder if there should rather be a Kconfig option so each board
can select it's env file name; default would be "<board>.env".
what do you think?

Best regards,

Wolfgang Denk

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