[U-Boot] [PATCH v3 5/5] RFC: tegra: Convert to using environment files

[Stephen Warren <swarren@wwwdotorg.org>]

On 10/28/2013 04:15 PM, Simon Glass wrote:
> Hi Stephen,
> 
> On Mon, Oct 28, 2013 at 3:20 PM, Stephen Warren <swarren@wwwdotorg.org> wrote:
>> On 10/28/2013 02:50 PM, Simon Glass wrote:
>>> Hi Stephen,
>>>
>>> On Mon, Oct 28, 2013 at 2:41 PM, Stephen Warren <swarren@wwwdotorg.org> wrote:
>>>> On 10/28/2013 02:34 PM, Simon Glass wrote:
>>>>> Hi Stephen,
>>>>>
>>>>> On Mon, Oct 28, 2013 at 1:59 PM, Stephen Warren <swarren@wwwdotorg.org> wrote:
>>>>>> On 10/25/2013 11:01 PM, Simon Glass wrote:
>>>>>>> This seems more intuitive that the current #define way of doing things.
>>>>>>> The resulting code is shorter, avoids the quoting and line continuation
>>>>>>> pain, and also improves the clumsy way that stdio variables are created:
>>
>>>>>>> diff --git a/board/nvidia/env/common.env b/board/nvidia/env/common.env
>>>>>>
>>>>>>> +bootcmd_mmc0=setenv devnum 0; run mmc_boot
>>>>>>> +bootcmd_mmc1=setenv devnum 1; run mmc_booxt
>>>>>>> +boot_targets+= mmc1 mmc0
>>>>>>
>>>>>> I still don't see why = needs no space before/after, but += needs no
>>>>>> space before, but a space after. That simply looks like a typo to me,
>>>>>> and I'd be inclined to fix it were I editing this file. If a sed script
>>>>>> can't handle more flexible white-space, perhaps use Python or perhaps
>>>>>> Perl instead?
>>>>>
>>>>> The old code was similar, in that it had a space after the quote.
>>>>>
>>>>> We need the string to contain "mmc0 mmc1 usb0 dhcp" or perhaps "mmc0
>>>>> mmc1". I chose to add a space at the start of each string, but
>>>>> certainly we need a space somewhere, or we get "mmc0mmc1usb0dhcp".
>>>>
>>>> Oh, I see. I thought the space was part of the += syntax, not the value.
>>>> Perhaps to make that more obvious, you could allow:
>>>>
>>>> # No space added to value
>>>> var+=value
>> ...
>>>> var += "value1 value2"
>>>>
>>>> # One space included at start of addition to value
>>>> var+=" value1 value2"
>>>> var+= " value1 value2"
>>>> var +=" value1 value2"
>>>> var += " value1 value2"
>>>
>>> I was deliberately trying to avoid using quotes, since then it is
>>> really hard when you actually mean 'quote'.
>>
>> Hmm. On the other hand, quoting is standard syntax in any scripting
>> language.
>>
>>> For example at present you can put this in an env script at present,
>>> but how would you do it if quotes are special?
>>
>> Just escape it; " goes around the string and \" or "" within the string.
>> This seems pretty common...
> 
> Quoting quotes is currently needed for the header file. So how would
> my feature actually improve things?
> 
> Between this and Wolfgang's \ at newline I am wondering if this
> feature will actually improve anything? It we are really going to
> insist on making the .env file like a C string then I'm not sure what
> we gain.

I guess I don't really see much wrong with the current header file
approach. The benefits this patch provide are the ability to use += and
omit the \0. Maintaining a more typical " and \ based quoting system
seem fine though. I guess you could avoid the need for \ by using either
shell-style here documents:

var += <<<ENDOFHERE
   data
   more data
ENDOFHERE

or Python-style triple-quotes:

var += """
   data
   more data"""

either of which would degenerate to allowing the following when
multi-line and leading/trailing spaces weren't required:

var += value

... although I like the idea of requiring quotes, thus making that:

var += "value"