[PATCH v2 1/1] kbuild: dtc: Allow adding device tree fragments via config

[Trent Piepho]

There are no defconfigs that begin with a digit, but I guess there are
dts names that do.

Should probably just change the macro name from FOO_BOARD_DTS to DTS_FOO_BOARD.


On Wed, Jan 26, 2022 at 4:29 AM Antony Pavlov <antonynpavlov at gmail.com> wrote:
>
> On Wed, 22 Sep 2021 11:13:36 -0700
> Trent Piepho <trent.piepho at igorinstitute.com> wrote:
>
> Hi!
>
> This patch was applied to barebox source tree as
>
>   2ae7ac7ab2 kbuild: dtc: Allow adding device tree fragments via config
>
> With this patch I see build error if device tree file name starts with digit (0-9),
> e.g.:
>
>   barebox$ git checkout v2022.01.0
>
>   barebox$ make mrproper
>
>   barebox$ export ARCH=arm
>   barebox$ export CROSS_COMPILE=arm-none-eabi-
>   barebox$ sed -i "s/virt2real.dtb/2virt2real.dtb/" arch/arm/dts/Makefile
>   barebox$ mv arch/arm/dts/virt2real.dts arch/arm/dts/2virt2real.dts
>
>   barebox$ make virt2real_defconfig
>   ...
>   barebox$ make -s
>   <stdin>:1:9: error: macro names must be identifiers                                              make[1]:  [scripts/Makefile.lib:352: arch/arm/dts/2virt2real.dtb] Error 1
>   make:  [Makefile:952: arch/arm/dts] Error 2
>
>
>
>
> > This introduces a config variable that allows adding additional fragments
> > to the Barebox device tree(s).
> >
> > Example uses are adjusting the flash partition layout, adding barebox
> > state variables, or adding an I2C device.  These can be now be done with
> > build configuration only, without needing to patch the existing dts
> > files in the Barebox source.
> >
> > The advantage is greater when an external build system, such as Yocto or
> > Buildroot, is being used to build Barebox.  The build system can drop in
> > a dts fragment to partition flash and build from unaltered Barebox
> > source.  This avoids the need for cumbersome maintenance of patch files
> > to modify Barebox's source for each flash partition layout.
> >
> > Preprocessing the dts file gains another layer, where a generated dts
> > source consisting of an include directive for the original dts source is
> > followed by more includes for each fragment.  This is piped to the
> > existing preprocessor call on stdin to avoid another temporary file.
> > cpp/dtc will correctly identify errors in the source files they occur
> > in.  The -MT option is used so the cpp auto-dependencies reference the
> > original dts source and not the generated code passed on stdin.
> >
> > A preprocessor macro named after the base dts file, e.g. foo-bar.dts
> > will define foo_bar_dts, will be defined so that the fragments can
> > possibly operate differently based on which image's dts is being built.
> >
> > Signed-off-by: Trent Piepho <trent.piepho at igorinstitute.com>
> > ---
> > Changes from v1:
> >   - Remove 2nd config variable for in-tree fragments.
> >   - Add macro to preproccessed dts
> >
> >  common/Kconfig       | 18 ++++++++++++++++++
> >  scripts/Makefile.lib |  8 +++++++-
> >  2 files changed, 25 insertions(+), 1 deletion(-)
> >
> > diff --git a/common/Kconfig b/common/Kconfig
> > index a9feae2ae..6fdc14148 100644
> > --- a/common/Kconfig
> > +++ b/common/Kconfig
> > @@ -1091,6 +1091,24 @@ config SYSTEMD_OF_WATCHDOG
> >         in the kernel device tree. If the kernel is booted without a device
> >         tree or with one that lacks aliases, nothing is added.
> >
> > +config EXTERNAL_DTS_FRAGMENTS
> > +     string "external dts file fragments"
> > +     depends on OFTREE
> > +     help
> > +       List of dts fragment files that will be appended to Barebox's device
> > +       tree(s) source when building the dtb file(s).  If multiple files are
> > +       listed, they will be appended in order.  Relative filenames will use
> > +       the dtc include search path.
> > +
> > +       A preprocessor macro based on the name of the main dts will be
> > +       defined, which allows the dts fragments to based on which image of a
> > +       multi image build they are being used in.
> > +
> > +       It not intended that this be put into into Barebox defconfig files.
> > +       Instead, it's an external build system, like Yocto or buildroot, to
> > +       add dts fragments from outside the Barebox source tree into the
> > +       Barebox build.
> > +
> >  menu "OP-TEE loading"
> >
> >  config OPTEE_SIZE
> > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> > index 80d76b177..4496f1a70 100644
> > --- a/scripts/Makefile.lib
> > +++ b/scripts/Makefile.lib
> > @@ -201,6 +201,7 @@ cpp_flags      = -Wp,-MD,$(depfile) $(NOSTDINC_FLAGS) $(__cpp_flags)
> >  ld_flags       = $(KBUILD_LDFLAGS) $(ldflags-y)
> >
> >  dtc_cpp_flags  = -Wp,-MD,$(depfile).pre -nostdinc                        \
> > +              -Wp,-MT,$(basename $(notdir $@)).o                      \
> >                -I$(srctree)/arch/$(SRCARCH)/dts/include                \
> >                -I$(srctree)/dts/include                                \
> >                -I$(srctree)/include                                    \
> > @@ -335,8 +336,13 @@ cmd_dt_S_dtb = $(srctree)/scripts/gen-dtb-s $(subst -,_,$(*F)) $< $(CONFIG_IMD)
> >  $(obj)/%.dtb.S: $(obj)/%.dtb $(srctree)/scripts/gen-dtb-s FORCE
> >       $(call if_changed,dt_S_dtb)
> >
> > +dts-frags = $(subst $(quote),,$(CONFIG_EXTERNAL_DTS_FRAGMENTS))
> >  quiet_cmd_dtc = DTC     $@
> > -cmd_dtc = $(CPP) $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
> > +# For compatibility between make 4.2 and 4.3
> > +H := \#
> > +cmd_dtc = /bin/echo -e '$(H)define $(subst -,_,$(*F))_dts 1\n'$(foreach f,$< $(dts-frags),'$(H)include "$(f)"\n') | \
> > +     $(CPP) $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) - ; \
> >       $(objtree)/scripts/dtc/dtc -O dtb -o $@ -b 0 \
> >               -i $(srctree)/arch/$(SRCARCH)/dts $(DTC_FLAGS) \
> >               -i $(srctree)/dts/src/$(SRCARCH) \
> > --
> > 2.31.1
> >
> >
> > _______________________________________________
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> > barebox at lists.infradead.org
> > http://lists.infradead.org/mailman/listinfo/barebox
>
>
> --
> Best regards,
>   Antony Pavlov