Re: [RFC PATCH dtc] C-based DT schema checker integrated into dtc

[Rob Herring <rob.herring@calxeda.com>]

On 10/25/2013 10:21 AM, Jon Loeliger wrote:
>> On 10/25/2013 12:43 AM, Grant Likely wrote:
>>> On Thu, 24 Oct 2013 22:51:28 +0100, Stephen Warren <swarren@wwwdotorg.org> 
>> wrote:
>>>> From: Stephen Warren <swarren@nvidia.com>
>>>>
>>>> This is a very quick proof-of-concept re: how a DT schema checker might
>>>> look if written in C, and integrated into dtc.
>>>
>>> Thanks for looking at this.
>>>
>>> Very interesting. Certainly an expedient way to start checking schemas,
>>> and for certain bindings it may be the best approach. The downside is it
>>> forces a recompilation of DTC to bring in new bindings and it isn't a
>>> great meduim for mixing schema with documentation in the bindings.
>>
>> This approach would certainly require recompiling something. I threw the
>> code into dtc simply because it was the easiest container for the
>> demonstration. It could be a separate DT validation utility if we
>> wanted, although we'd need to split the DT parser from dtc into a
>> library to avoid code duplication. The resultant utility could be part
>> of the repo containing the DTs, so it didn't end up as a separate
>> package to manage.
>>
>> I think the additional documentation could be added as comments in the
>> validation functions, just like IIRC it was to be represented as
>> comments even in the .dts-based schema proposals.
> 
> DTers,
> 
> I think the additional benefit of starting with a direct C
> implementation is that it causes us to begin to actually
> codify the schema requirements.  Sure, it may not be ideal
> at first, but over time it may reveal consistent patterns
> that can be extracted.  And it may reveal what a real schema
> might look like and how it might be expressed better.  Which
> is to say that perhaps we are letting "perfect" get in the
> way of "good enough to start"?
> 
> In the meantime, someone has shown us the code and we can
> get started.  It's a Small Matter of Refactoring later. :-)

I have not really looked at whether this would make sense or be low
effort, but what if Grant's run-time checker was converted to run at
kernel compile time. That would fall into the get something working
sooner rather than later, but doesn't solve the documentation problem
either.

Rob