default environment append from kconfig

[Rasmus Villemoes]

On 09/08/2022 12.47, Francesco Dolcini wrote:
> Hello all,
> is there any kconfig mechanism in u-boot to append environment variable to the
> default one?
> 

Well, despite the name, CONFIG_EXTRA_ENV_SETTINGS is not settable via
kconfig, but only from board header file. And while it works, it's
rather cumbersome to maintain that macro expanding to a string with all
the embedded \0 and the required \ continuations etc.

> I am aware of CONFIG_USE_DEFAULT_ENV_FILE, but this will completely
> replace it, looking into the code I was not able to find anything, 

You could select CONFIG_ENV_IMPORT_FDT, then populate the
/config/environment/ devicetree node with the key/value pairs you want.

This can for example be done via the <board>-u-boot.dtsi file, or if
you're using an in-tree board with in-tree .dts, and just want to
maintain your own .config and environment out of tree, you could
additionally set CONFIG_DEVICE_TREE_INCLUDES to point at a .dtsi which
just has that

/ {
  config {
    environment {
      foo = "bar";
    };
  };
};

(that was exactly a use case I had in mind for
CONFIG_DEVICE_TREE_INCLUDES, as can be seen in the commit log for
a77f468099).

Rasmus