[PATCH v8 4/8] env: Allow U-Boot scripts to be placed in a .env file

[Tom Rini]

On Mon, Oct 18, 2021 at 12:13:18PM -0600, Simon Glass wrote:

> At present U-Boot environment variables, and thus scripts, are defined
> by CONFIG_EXTRA_ENV_SETTINGS. It is painful to add large amounts of text
> to this file and dealing with quoting and newlines is harder than it
> should be. It would be better if we could just type the script into a
> text file and have it included by U-Boot.
> 
> Add a feature that brings in a .env file associated with the board
> config, if present. To use it, create a file in a board/<vendor>
> directory, typically called <board>.env and controlled by the
> CONFIG_ENV_SOURCE_FILE option.
> 
> The environment variables should be of the form "var=value". Values can
> extend to multiple lines. See the README under 'Environment Variables:'
> for more information and an example. Note that environment variables may
> not end in + but can start with other strange characters, including
> underscore, comma and slash.
> 
> In many cases environment variables need access to the U-Boot CONFIG
> variables to select different options. Enable this so that the environment
> scripts can be as useful as the ones currently in the board config files.
> This uses the C preprocessor, means that comments can be included in the
> environment using /* ... */
> 
> Also support += to allow variables to be appended to. This is needed when
> using the preprocessor.
> 
> Signed-off-by: Simon Glass <sjg at chromium.org>

As much as I and others appreciate that you've written the parser here
in a classic UNIX tool, awk, since a lot of the problems also seem to
stem from having the parser be able to handle previously valid
environment variables, if this was written in Python say, would we have
this problem?

-- 
Tom
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