[U-Boot] [PATCH] Allow U-Boot scripts to be placed in a .env file

[Otavio Salvador]

On Tue, Apr 23, 2013 at 11:36 PM, Simon Glass <sjg at chromium.org> wrote:
> Hi Otavio,
>
> On Tue, Apr 23, 2013 at 7:14 PM, Otavio Salvador
> <otavio at ossystems.com.br> wrote:
>> On Tue, Apr 23, 2013 at 9:29 PM, Simon Glass <sjg at chromium.org> wrote:
>>> Hi Tom,
>>>
>>> On Tue, Apr 23, 2013 at 4:33 PM, Tom Rini <trini at ti.com> wrote:
>>>> On Tue, Apr 23, 2013 at 02:32:00PM -0700, Simon Glass wrote:
>>>>> Hi Wolfgang,
>>>>>
>>>>> On Tue, Apr 16, 2013 at 10:44 PM, Wolfgang Denk <wd at denx.de> wrote:
>>>>> > Dear Simon Glass,
>>>>> >
>>>>> > In message <1366155414-6525-1-git-send-email-sjg at chromium.org> 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 include/configs
>>>>> >> with the same name as you could board config file, except with a
>>>>> >> .env extension instead of a .h extension. The variables should be
>>>>> >> separated by \0. Comments are permitted, using # as the first character
>>>>> >> in a line.
>>>>> >
>>>>> > Please do not litter the include/configs/ directory with such stuff.
>>>>> > It's more than big enough already.  Please put such files into the
>>>>> > respective board directories.
>>>>>
>>>>> OK.
>>>>>
>>>>> >
>>>>> > And if you do something like this, then please go the way to the end.
>>>>> > Forget about the \0 termination, make it a plain text file instead,
>>>>> > something that can be used with "env import -t" as well (or created
>>>>> > with "env export -t").
>>>>>
>>>>> I'm not sure how to do this. Doesn't this mean that we cannot add
>>>>> multi-line scripts to the environment? That was part of my aim. But if
>>>>> I put a 0x0a in the script then it will think we are starting a new
>>>>> variable.
>>>>
>>>> The first thing that pops to mind is:
>>>> 1) embedded the text file into a linker-known spot
>>>> 2) Make part of the default env setup process be to env import -t that
>>>> location in memory.
>>>
>>> Well I have a working implementation - my concern was more about how
>>> to deal with newlines. I would like to be able to handle a script just
>>> written out over multiple lines in a text file. This is really nice
>>> because we can have proper indenting, comments, etc. As soon as we
>>> have to use 0x0a as the separator between each environment variable
>>> that is no longer possible.
>>>
>>> My current scheme requires the .env file to have \0 separating
>>> environment variables which is obviously not ideal. I am hoping we can
>>> find another way which is more textfile-friendly without losing the
>>> benefits.
>>
>> What about using \ as continuous line indicator and otherwise finish
>> the line, when parsing, wiht \0?
>
> Thanks for the suggestion. But that, along with the need for quotes,
> is one of the reasons I would like to provide a way to enter scripts
> naturally.
>
> Adding \ at the end of each line is error-prone and gets in the way.
> Python and C don't have this requirement - so why should U-Boot
> scripts?
>
> I wonder if we could define that 'xxx=' at the start of a line
> delineates a new variable?

The problem with this kind of thing is we might end doing a full
parser and doing a semantic interpret of the text. It seems to be way
too complex ...

--
Otavio Salvador                             O.S. Systems
E-mail: otavio at ossystems.com.br  http://www.ossystems.com.br
Mobile: +55 53 9981-7854              http://projetos.ossystems.com.br