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

Simon Glass
2021-10-19T14:11:28Z

Hi Tom,

On Tue, 19 Oct 2021 at 08:07, Tom Rini <trini@konsulko.com> wrote:
>
> 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@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?

Well ideally I'd like to avoid Python in this case as it is in the
compilation path. I am not sure yet what Wolfgang actually wants,
apart from variable names ending with + which I would like to
disallow.

So if we can clearly understand the goal, then we might be able to do
it in awk, but, again, can we just disallow '+' in var names ?

Regards,
Simon