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

[Simon Glass]

Hi Otavio,

On Tue, Apr 23, 2013 at 7:44 PM, Otavio Salvador
<otavio at ossystems.com.br> wrote:
> 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 ...

I can do the above with a simple sed script.

Do you mean we might create a new type of parser? If so, then we could
perhaps use a .scr extension or similar. My idea here is specifically
for environment.

Regards,
Simon