[U-Boot] [PATCH 01/15] fdt: Use sed instead of cpp to pre-process the dtc

[Simon Glass]

Hi Stephen,

On Fri, Dec 28, 2012 at 3:47 PM, Stephen Warren <swarren at wwwdotorg.org> wrote:
> On 12/28/2012 11:07 AM, Simon Glass wrote:
>> Hi,
>>
>> On Fri, Dec 28, 2012 at 8:42 AM, Mike Frysinger <vapier at gentoo.org> wrote:
>>> On Friday 28 December 2012 09:55:52 Simon Glass wrote:
>>>> On Thu, Dec 27, 2012 at 4:03 PM, Stephen Warren wrote:
>>>>> On 12/26/2012 03:28 PM, Simon Glass wrote:
>>>>>> Include file support in dtc is still not available in common
>>>>>> distributions so we need to keep our preprocessing arrangement around
>>>>>> for a little longer.
>>>>>>
>>>>>> But # is commonly used in FDT files, so use sed instead of cpp for this
>>>>>> preprocessing.
>>>>>
>>>>> This sounds like the wrong approach to me. I'd suggest using what I
>>>>>
>>>>> proposed for the kernel:
>>>>>> cmd_dtc_cpp = $(CPP) $(cpp_flags) -D__DTS__ -x assembler-with-cpp -o
>>>>>> $(dtc-tmp) $< ; \
>>>>>>
>>>>>>         $(objtree)/scripts/dtc/dtc -O dtb -o $@ -b 0 $(DTC_FLAGS)
>>>>>>         $(dtc-tmp)
>>>>>
>>>>> The "-x assembler-with-cpp" is what solves the # problem IIRC.
>>>>
>>>> I originally used CPP as an expedient means of converting the
>>>> ARCH_CPU_DTS symbol until we all have a dtc with include path support.
>>>>
>>>> Are you saying that we want to actually use the CPP on tthe device
>>>> tree and (presumably) use U-Boot include files within the FDT?
>
> Yes, I'd explicitly like to be able to use C-style header files to
> define named constants etc.
>
>>> sounds reasonable to me.  we already do it with linker scripts, and if the
>>> kernel is doing it, it means we can (possibly) share more.
>>
>> OK. Stephen, what is the kernel actually doing with the preprocessor?
>> Have you given up on the dtc symbol stuff for now and plan to use CPP
>> instead?
>
> Yes, I've given up on getting any kind of pre-processor or macro
> language into dtc itself. I haven't managed to get the kernel to accept
> the logic I quoted above either yet; this has all been a very long and
> tortuous process. I hope to repost the patch that implements this in the
> kernel within the next week or so.

OK good luck with the cat-herding. I will update this patch along the
lines you describe above and resend. I hope we are not opening a can
of worms using the full power of the pre-processor, but clearly we are
not getting anywhere with dtc, so this is the only reasonable option.

Regards,
Simon