On Fri, Oct 22, 2021 at 10:29:26AM +0200, Wolfgang Denk wrote:
Dear Simon,
In message 20211021210847.v10.3.Ie78bfbfca0d01d9cba501e127f446ec48e1f7afe@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".
I feel I should preface this with "I am cranky". Now I see that I can indeed do: => setenv foo\bar baz => printenv foo\bar foo\bar=baz
on a system today. To what value, I know not. I can see how you write some fancy state machine set of scripts where you end up with "foo+bar+" needing to be set because you do a bunch of probing of things at run time and concatenate and ... there, we've got a variable that ends in + (and fwiw, sh says baz+ is a bad variable name, bash gets kinda funny with it). I don't see the value in allowing "" in a variable name, nor can I make bash nor sh handle that. We can just disallow "" in variable names.