[PATCH v3 6/9] kbuild: consolidate Devicetree dtb build rules

[Rob Herring]

On Mon, Sep 10, 2018 at 10:04 AM Rob Herring <robh at kernel.org> wrote:
>
> There is nothing arch specific about building dtb files other than their
> location under /arch/*/boot/dts/. Keeping each arch aligned is a pain.
> The dependencies and supported targets are all slightly different.
> Also, a cross-compiler for each arch is needed, but really the host
> compiler preprocessor is perfectly fine for building dtbs. Move the
> build rules to a common location and remove the arch specific ones. This
> is done in a single step to avoid warnings about overriding rules.
>
> The build dependencies had been a mixture of 'scripts' and/or 'prepare'.
> These pull in several dependencies some of which need a target compiler
> (specifically devicetable-offsets.h) and aren't needed to build dtbs.
> All that is really needed is dtc, so adjust the dependencies to only be
> dtc.
>
> This change enables support 'dtbs_install' on some arches which were
> missing the target.

[...]

> @@ -1215,6 +1215,33 @@ kselftest-merge:
>                 $(srctree)/tools/testing/selftests/*/config
>         +$(Q)$(MAKE) -f $(srctree)/Makefile olddefconfig
>
> +# ---------------------------------------------------------------------------
> +# Devicetree files
> +
> +ifneq ($(wildcard $(srctree)/arch/$(SRCARCH)/boot/dts/),)
> +dtstree := arch/$(SRCARCH)/boot/dts
> +endif
> +
> +ifdef CONFIG_OF_EARLY_FLATTREE

This can be true when dtstree is unset. So this line should be this
instead to fix the 0-day reported error:

ifneq ($(dtstree),)

> +
> +%.dtb : scripts_dtc
> +       $(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
> +
> +PHONY += dtbs dtbs_install
> +dtbs: scripts_dtc
> +       $(Q)$(MAKE) $(build)=$(dtstree)
> +
> +dtbs_install: dtbs
> +       $(Q)$(MAKE) $(dtbinst)=$(dtstree)
> +
> +all: dtbs
> +
> +endif