[PATCH v2 6/9] kbuild: consolidate Devicetree dtb build rules

[Rob Herring]

On Fri, Sep 7, 2018 at 5:33 AM Masahiro Yamada
<yamada.masahiro at socionext.com> wrote:
>
> 2018-09-06 8:53 GMT+09:00 Rob Herring <robh at kernel.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 at socionext.com>
> > Cc: Michal Marek <michal.lkml at markovi.net>
> > Cc: Vineet Gupta <vgupta at synopsys.com>
> > Cc: Russell King <linux at armlinux.org.uk>
> > Cc: Catalin Marinas <catalin.marinas at arm.com>
> > Cc: Will Deacon <will.deacon at arm.com>
> > Cc: Yoshinori Sato <ysato at users.sourceforge.jp>
> > Cc: Michal Simek <monstr at monstr.eu>
> > Cc: Ralf Baechle <ralf at linux-mips.org>
> > Cc: Paul Burton <paul.burton at mips.com>
> > Cc: James Hogan <jhogan at kernel.org>
> > Cc: Ley Foon Tan <lftan at altera.com>
> > Cc: Benjamin Herrenschmidt <benh at kernel.crashing.org>
> > Cc: Paul Mackerras <paulus at samba.org>
> > Cc: Michael Ellerman <mpe at ellerman.id.au>
> > Cc: Chris Zankel <chris at zankel.net>
> > Cc: Max Filippov <jcmvbkbc at gmail.com>
> > Cc: linux-kbuild at vger.kernel.org
> > Cc: linux-snps-arc at lists.infradead.org
> > Cc: linux-arm-kernel at lists.infradead.org
> > Cc: uclinux-h8-devel at lists.sourceforge.jp
> > Cc: linux-mips at linux-mips.org
> > Cc: nios2-dev at lists.rocketboards.org
> > Cc: linuxppc-dev at lists.ozlabs.org
> > Cc: linux-xtensa at linux-xtensa.org
> > Signed-off-by: Rob Herring <robh at kernel.org>
> > ---
> > Please ack so I can take the whole series via the DT tree.
> >
> > v2:
> >  - Fix $arch/boot/dts path check for out of tree builds
> >  - Fix dtc dependency for building built-in dtbs
> >  - Fix microblaze built-in dtb building
>
>
> This breaks parallel building
> because two threads could descend into scripts/dtc
> at the same time.
>
> 'all' depends on both 'scripts' and 'dtc'.
>
> * 'scripts' target -- descends into scripts/, then scripts/dtc
> * 'dtc' target     -- descents into scripts/dtc directly

Any suggestions for how to fix given the problem with depending on
scripts? I suppose I could make scripts depend on dtc instead, but I'd
be back to needing to fix cleaning. Or I could just skip removing the
cross compiler dependency for now.

Rob