[PATCH v10 3/9] env: Allow U-Boot scripts to be placed in a .env file

[Wolfgang Denk]

Dear Simon,

In message <20211021210847.v10.3.Ie78bfbfca0d01d9cba501e127f446ec48e1f7afe at changeid> you 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.

The README does not contain this information as it has been moved
into doc/usage/environment.rst

I think the documentation is lacking a hint that multiline
definitions will always be separated by spaces.

> Also support += to allow variables to be appended to. This is needed when
> using the preprocessor.

I cannot see what the preprocessor has to do with this feature.  It
would be useful in any case, even without the preporcessor.


The documentation reads:

"Variables can contain `+` characters but in the unlikely
event that you want to have a variable name ending in plus, put a backslash
before the `+` so that the script knows you are not adding to an existing
variable but assigning to a new one::
 
    maximum\+=value
"

However, '\' is also a legal character in a variable name (and
doubled backslashes or apostrophes etc. are legal, too), so
above line should actually set the environment variable "maximum\+"
to "value".

Best regards,

Wolfgang Denk

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