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

From: Masahiro Yamada <yamada.masahiro@socionext.com>
To: Rob Herring <robh@kernel.org>
Cc: DTML <devicetree@vger.kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Frank Rowand <frowand.list@gmail.com>,
	Michal Marek <michal.lkml@markovi.net>,
	Vineet Gupta <vgupta@synopsys.com>,
	Russell King <linux@armlinux.org.uk>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Michal Simek <monstr@monstr.eu>,
	Ralf Baechle <ralf@linux-mips.org>,
	James Hogan <jhogan@kernel.org>,
	Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>,
	Chris Zankel <chris@zankel.net>,
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	Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
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	Paul Burton <paul.burton@mips.com>,
	Ley Foon Tan <ley.foon.tan@intel.com>
Subject: Re: [PATCH v3 6/9] kbuild: consolidate Devicetree dtb build rules
Date: Wed, 12 Sep 2018 10:00:49 +0900	[thread overview]
Message-ID: <CAK7LNAQFqhWw+LwDoypGG=OP6tH4qf2tT=LvtchK2GoiNyzDXg@mail.gmail.com> (raw)
In-Reply-To: <CAL_Jsq+=VbdcVLiwXbOA5d+R2YY6=2Pw2bQpci-jj-JvereD1A@mail.gmail.com>

2018-09-12 0:40 GMT+09:00 Rob Herring <robh@kernel.org>:
> On Mon, Sep 10, 2018 at 10:04 AM Rob Herring <robh@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

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
         ...

-- 
Best Regards
Masahiro Yamada