[PATCH V8] kbuild: create a rule to run the pre-processor on *.dts files

[Rob Herring]

On 02/08/2013 08:45 AM, Grant Likely wrote:
> On Tue,  5 Feb 2013 12:06:28 -0700, Stephen Warren <swarren at wwwdotorg.org> wrote:
>> From: Stephen Warren <swarren at nvidia.com>
>>
>> Create cmd_dtc_cpp to run the C pre-processor on *.dts file before
>> passing them to dtc for final compilation. This allows the use of #define
>> and #include within the .dts file.
>>
>> Acked-by: Simon Glass <sjg at chromium.org>
>> Acked-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj at jcrosoft.com>
>> Acked-by: Michal Marek <mmarek at suse.cz>
>> Acked-by: Srinivas Kandagatla <srinivas.kandagatla at st.com>
>> Signed-off-by: Stephen Warren <swarren at nvidia.com>
> 
> I've applied this and was going to push it out, but I've just thought of
> a problem that could be a show stopper. Once a dtsp file includes a C
> header, the contents of that header become part of the Device Tree ABI.
> If someone changes that file (ie. to renumber a series of #defines) then
> that will break the binding. We need a way to protect against that.
> Someone changing a .h file may make the assumption that it is only
> kernel internal and won't realize that it has external implications.
> 
> I'm thinking that any dts includes need to be treated in the same way as
> userspace headers. We could put them into include/uapi and piggy back on
> the protection already afforded by that directory, or come up with
> something new. Any thoughts?

Also, we would never be able to separate the dts files from the kernel
tree without some separation.

Rob