linux-kernel - Re: [PATCH 6/8] kbuild: consolidate Devicetree dtb build rules

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Date:   Sun, 26 Aug 2018 18:56:14 -0500
From:   Rob Herring <robh@...nel.org>
To:     Masahiro Yamada <yamada.masahiro@...ionext.com>
Cc:     devicetree@...r.kernel.org,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Michal Marek <michal.lkml@...kovi.net>,
        Vineet Gupta <vgupta@...opsys.com>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Michal Simek <monstr@...str.eu>,
        Ralf Baechle <ralf@...ux-mips.org>,
        Paul Burton <paul.burton@...s.com>,
        James Hogan <jhogan@...nel.org>,
        Ley Foon Tan <lftan@...era.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        arcml <linux-snps-arc@...ts.infradead.org>,
        "moderated list:ARM/FREESCALE IMX / MXC ARM ARCHITECTURE" 
        <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:H8/300 ARCHITECTURE" 
        <uclinux-h8-devel@...ts.sourceforge.jp>,
        Linux-MIPS <linux-mips@...ux-mips.org>,
        nios2-dev@...ts.rocketboards.org,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-xtensa@...ux-xtensa.org
Subject: Re: [PATCH 6/8] kbuild: consolidate Devicetree dtb build rules

On Sat, Aug 25, 2018 at 9:06 PM Masahiro Yamada
<yamada.masahiro@...ionext.com> wrote:
>
> Hi Rob,
>
>
> 2018-08-22 6:55 GMT+09:00 Rob Herring <robh@...nel.org>:
> > 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.
> >
> > Cc: Masahiro Yamada <yamada.masahiro@...ionext.com>
> > Cc: Michal Marek <michal.lkml@...kovi.net>
> > Cc: Vineet Gupta <vgupta@...opsys.com>
> > Cc: Russell King <linux@...linux.org.uk>
> > Cc: Catalin Marinas <catalin.marinas@....com>
> > Cc: Will Deacon <will.deacon@....com>
> > Cc: Yoshinori Sato <ysato@...rs.sourceforge.jp>
> > Cc: Michal Simek <monstr@...str.eu>
> > Cc: Ralf Baechle <ralf@...ux-mips.org>
> > Cc: Paul Burton <paul.burton@...s.com>
> > Cc: James Hogan <jhogan@...nel.org>
> > Cc: Ley Foon Tan <lftan@...era.com>
> > Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
> > Cc: Paul Mackerras <paulus@...ba.org>
> > Cc: Michael Ellerman <mpe@...erman.id.au>
> > Cc: Chris Zankel <chris@...kel.net>
> > Cc: Max Filippov <jcmvbkbc@...il.com>
> > Cc: linux-kbuild@...r.kernel.org
> > Cc: linux-snps-arc@...ts.infradead.org
> > Cc: linux-arm-kernel@...ts.infradead.org
> > Cc: uclinux-h8-devel@...ts.sourceforge.jp
> > Cc: linux-mips@...ux-mips.org
> > Cc: nios2-dev@...ts.rocketboards.org
> > Cc: linuxppc-dev@...ts.ozlabs.org
> > Cc: linux-xtensa@...ux-xtensa.org
> > Signed-off-by: Rob Herring <robh@...nel.org>
> > ---
> >  Makefile                 | 30 ++++++++++++++++++++++++++++++
> >  arch/arc/Makefile        |  6 ------
> >  arch/arm/Makefile        | 20 +-------------------
> >  arch/arm64/Makefile      | 17 +----------------
> >  arch/c6x/Makefile        |  2 --
> >  arch/h8300/Makefile      | 11 +----------
> >  arch/microblaze/Makefile |  4 +---
> >  arch/mips/Makefile       | 15 +--------------
> >  arch/nds32/Makefile      |  2 +-
> >  arch/nios2/Makefile      |  7 -------
> >  arch/nios2/boot/Makefile |  4 ----
> >  arch/powerpc/Makefile    |  3 ---
> >  arch/xtensa/Makefile     | 12 +-----------
> >  scripts/Makefile         |  1 -
> >  scripts/Makefile.lib     |  2 +-
> >  15 files changed, 38 insertions(+), 98 deletions(-)
> >
> > diff --git a/Makefile b/Makefile
> > index c13f8b85ba60..6d89e673f192 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -1212,6 +1212,30 @@ kselftest-merge:
> >                 $(srctree)/tools/testing/selftests/*/config
> >         +$(Q)$(MAKE) -f $(srctree)/Makefile olddefconfig
> >
> > +# ---------------------------------------------------------------------------
> > +# Devicetree files
> > +
> > +dtstree := $(wildcard arch/$(SRCARCH)/boot/dts)

BTW, there's an error here too. It doesn't work right with
KBUILD_OUTPUT set and should be:

ifneq ($(wildcard $(srctree)/arch/$(SRCARCH)/boot/dts/),)
dtstree := arch/$(SRCARCH)/boot/dts
endif

> > +
> > +ifdef CONFIG_OF_EARLY_FLATTREE
> > +
> > +%.dtb %.dtb.S %.dtb.o: | dtc
>
> I think the pipe operator is unnecessary
> because Kbuild will descend to $(dtstree) anyway.

The pipe means 'order-only', right? So it is just a weaker dependency
for things which are not input files as dtc is not. The 'dtc' here is
just the dtc rule below, not the actual executable. Or am I missing
something?

> > +       $(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
> > +
> > +PHONY += dtbs
> > +dtbs: | dtc
>
> Ditto.
>
>
> > +       $(Q)$(MAKE) $(build)=$(dtstree)
> > +
> > +dtbs_install: dtbs
> > +       $(Q)$(MAKE) $(dtbinst)=$(dtstree)
> > +
> > +all: dtbs
> > +
> > +dtc:
> > +       $(Q)$(MAKE) $(build)=scripts/dtc
> > +
> > +endif
> > +
>
>
> arch/*/boot/dts/ are not only directories that
> require dtc.

Ah yes, of course...

> > diff --git a/scripts/Makefile b/scripts/Makefile
> > index 61affa300d25..a716a6b10954 100644
> > --- a/scripts/Makefile
> > +++ b/scripts/Makefile
> > @@ -39,7 +39,6 @@ build_unifdef: $(obj)/unifdef
> >  subdir-$(CONFIG_MODVERSIONS) += genksyms
> >  subdir-y                     += mod
> >  subdir-$(CONFIG_SECURITY_SELINUX) += selinux
> > -subdir-$(CONFIG_DTC)         += dtc
> >  subdir-$(CONFIG_GDB_SCRIPTS) += gdb
> >
> >  # Let clean descend into subdirs

Looks like I need to leave this line to fix the above and cleaning.

Thanks for the review.

Rob