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

[Grant Likely]

On Fri, 08 Feb 2013 15:24:25 -0600, Rob Herring <robherring2 at gmail.com> wrote:
> 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.

Good point. They better be in a completely separate directory then.

g.