linux-kernel - Re: [PATCH v3 6/9] kbuild: consolidate Devicetree dtb build rules

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Message-ID: <CAK7LNATkkOiYPj2RLubcgZ_z59Bhz4GkgWqPMbnaHBk7EisXLg@mail.gmail.com>
Date:   Sun, 23 Sep 2018 06:31:14 -0400
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
Cc:     Rob Herring <robh@...nel.org>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <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>,
        Yoshinori Sato <ysato@...rs.sourceforge.jp>,
        Michal Simek <monstr@...str.eu>,
        Ralf Baechle <ralf@...ux-mips.org>,
        James Hogan <jhogan@...nel.org>,
        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 <linux-kbuild@...r.kernel.org>,
        arcml <linux-snps-arc@...ts.infradead.org>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:H8/300 ARCHITECTURE" 
        <uclinux-h8-devel@...ts.sourceforge.jp>,
        Linux MIPS Mailing List <linux-mips@...ux-mips.org>,
        nios2-dev@...ts.rocketboards.org,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>,
        linux-xtensa@...ux-xtensa.org, Will Deacon <will.deacon@....com>,
        Paul Burton <paul.burton@...s.com>,
        Ley Foon Tan <ley.foon.tan@...el.com>
Subject: Re: [PATCH v3 6/9] kbuild: consolidate Devicetree dtb build rules

2018-09-13 11:51 GMT-04:00 Geert Uytterhoeven <geert@...ux-m68k.org>:
> Hi Yamada-san,
>
> On Wed, Sep 12, 2018 at 3:02 AM Masahiro Yamada
> <yamada.masahiro@...ionext.com> wrote:
>> 2018-09-12 0:40 GMT+09:00 Rob Herring <robh@...nel.org>:
>> > On Mon, Sep 10, 2018 at 10:04 AM Rob Herring <robh@...nel.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
>>
>>
>> Ah, right.
>> Even x86 can enable OF and OF_UNITTEST.
>>
>>
>>
>> Another solution might be,
>> guard it by 'depends on ARCH_SUPPORTS_OF'.
>>
>>
>>
>> This is actually what ACPI does.
>>
>> menuconfig ACPI
>>         bool "ACPI (Advanced Configuration and Power Interface) Support"
>>         depends on ARCH_SUPPORTS_ACPI
>>          ...
>
> ACPI is a real platform feature, as it depends on firmware.
>
> CONFIG_OF can be enabled, and DT overlays can be loaded, on any platform,
> even if it has ACPI ;-)
>

OK, understood.

Thanks!



-- 
Best Regards
Masahiro Yamada