Message-ID: <50759105.2000406@wwwdotorg.org>
Date: Wed, 10 Oct 2012 09:15:17 -0600
From: Stephen Warren <swarren@wwwdotorg.org>
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To: Scott Wood <scottwood@freescale.com>
CC: Mitch Bradley <wmb@firmworks.com>, Michal Marek <mmarek@suse.cz>,
        Stephen Warren <swarren@nvidia.com>,
        devicetree-discuss@lists.ozlabs.org, linux-kernel@vger.kernel.org
Subject: Re: dtc: import latest upstream dtc
References: <1349827466.26044.16@snotra>
In-Reply-To: <1349827466.26044.16@snotra>
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On 10/09/2012 06:04 PM, Scott Wood wrote:
> On 10/09/2012 06:20:53 PM, Mitch Bradley wrote:
>> On 10/9/2012 11:16 AM, Stephen Warren wrote:
>> > On 10/01/2012 12:39 PM, Jon Loeliger wrote:
>> >>>
>> >>> What more do you think needs discussion re: dtc+cpp?
>> >>
>> >> How not to abuse the ever-loving shit out of it? :-)
>> >
>> > Perhaps we can just handle this through the regular patch review
>> > process; I think it may be difficult to define and agree upon exactly
>> > what "abuse" means ahead of time, but it's probably going to be easy
>> > enough to recognize it when one sees it?
>>
>>
>> One of the ways it could get out of hand would be via "include
>> dependency hell".  People will be tempted to reuse existing .h files
>> containing pin definitions, which, if history is a guide, will end up
>> depending on all sorts of other .h files.
>>
>> Another problem I often face with symbolic names is the difficulty of
>> figuring out what the numerical values really are (for debugging),
>> especially when .h files are in different subtrees from the files that
>> use the definitions, and when they use multiple macro levels and fancy
>> features like concatenation.  Sometimes I think it's clearer just to
>> write the number and use a comment to say what it is.
> 
> Both comments apply just as well to ordinary C code, and I don't think
> anyone would seriously suggest just using comments instead for C code.
> 
> Is there a way to ask CPP to evaluate a macro in the context of the
> input file, rather than produce normal output?  If not, I guess you
> could make a tool that creates a wrapper file that includes the main
> file and then evaluates the symbol you want.

I'm not sure what "evaluate a macro in the context of the input file"
means. Macros are obviously already evaluated based on the current set
of macros defined by the file that's been processed or those it
included. Do you mean only allowing the use of macros in the current
file and not included files? What exactly would the wrapper you
mentioned do?

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