[RESEND PATCHv2 1/4] ARM: dts: add support for building DT overlays

Rob Herring robh+dt at kernel.org
Wed Sep 5 14:13:23 PDT 2018


On Wed, Sep 5, 2018 at 3:36 PM Frank Rowand <frowand.list at gmail.com> wrote:
>
> +cc: devicetree-compiler at vger.kernel.org
>
>      For context on the device-tree compiler list, this patch is for
>      the Linux kernel.
>
> On 09/04/18 01:05, Tero Kristo wrote:
> > Add simple support for building DT overlays. This just compiles any
> > given .dtso file under the base arch/arm/boot/dts directory into
> > a .dtbo.
> >
> > Signed-off-by: Tero Kristo <t-kristo at ti.com>
> > ---
> >  arch/arm/Makefile | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/arch/arm/Makefile b/arch/arm/Makefile
> > index d1516f8..ab555a0 100644
> > --- a/arch/arm/Makefile
> > +++ b/arch/arm/Makefile
> > @@ -339,7 +339,7 @@ $(BOOT_TARGETS): vmlinux
> >  $(INSTALL_TARGETS):
> >       $(Q)$(MAKE) $(build)=$(boot) MACHINE=$(MACHINE) $@
> >
> > -%.dtb: | scripts
> > +%.dtb %.dtbo: | scripts

This will need to change with my rework of the DT build rules[1].

> >       $(Q)$(MAKE) $(build)=$(boot)/dts MACHINE=$(MACHINE) $(boot)/dts/$@
> >
> >  PHONY += dtbs dtbs_install
> >
>
> The idea of adding knowledge of .dtso and .dtbo files to the dtc
> compiler, but that idea and the related patches have fallen by
> the wayside.
>
> Current overlay sources and blobs are properly handled by dtc when
> they are .dts and .dtb files.
>
> If the dtc compiler is updated with knowledge of .dtso and .dtbo
> then these changes would be needed.  At the moment the distinction
> of a .dtso and .dtbo is a naming convention that provides a clue
> about the intended use of the file.  But dtc does not know these
> file name extensions, requiring a specific flag to tell dtc to
> treat them as .dts or .dtb files.  I think the negative outweighs
> the positive for this patch.

I don't follow what you are proposing. We should decide on a convention though.

We shouldn't need .dtso because that is identified with the /plugin/
tag. Distinguishing overlay dtbs with .dtbo seems like a good idea
though.

Rob

[1] https://lkml.org/lkml/2018/8/21/770



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