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

Message ID 20180910150403.19476-7-robh@kernel.org
State New
Headers show
Series
  • Devicetree build consolidation
Related show

Commit Message

Rob Herring Sept. 10, 2018, 3:04 p.m.
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.

Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Paul Burton <paul.burton@mips.com>
Acked-by: Ley Foon Tan <ley.foon.tan@intel.com>
Cc: Masahiro Yamada <yamada.masahiro@socionext.com>
Cc: Michal Marek <michal.lkml@markovi.net>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: James Hogan <jhogan@kernel.org>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: linux-kbuild@vger.kernel.org
Cc: linux-snps-arc@lists.infradead.org
Cc: linux-arm-kernel@lists.infradead.org
Cc: uclinux-h8-devel@lists.sourceforge.jp
Cc: linux-mips@linux-mips.org
Cc: nios2-dev@lists.rocketboards.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-xtensa@linux-xtensa.org
Signed-off-by: Rob Herring <robh@kernel.org>
---
 Makefile                          | 35 ++++++++++++++++++++++++++++++-
 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/microblaze/boot/dts/Makefile |  2 ++
 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                  |  3 +--
 scripts/Makefile.lib              |  2 +-
 scripts/dtc/Makefile              |  2 +-
 17 files changed, 46 insertions(+), 101 deletions(-)

Comments

Rob Herring Sept. 11, 2018, 3:40 p.m. | #1
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
Masahiro Yamada Sept. 12, 2018, 1 a.m. | #2
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
         ...
Geert Uytterhoeven Sept. 13, 2018, 3:51 p.m. | #3
Hi Yamada-san,

On Wed, Sep 12, 2018 at 3:02 AM Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
> 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
>          ...

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 ;-)

Gr{oetje,eeting}s,

                        Geert
Masahiro Yamada Sept. 23, 2018, 10:31 a.m. | #4
2018-09-13 11:51 GMT-04:00 Geert Uytterhoeven <geert@linux-m68k.org>:
> Hi Yamada-san,
>
> On Wed, Sep 12, 2018 at 3:02 AM Masahiro Yamada
> <yamada.masahiro@socionext.com> wrote:
>> 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
>>          ...
>
> 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!
Rob Herring Sept. 28, 2018, 3:41 p.m. | #5
On Sun, Sep 23, 2018 at 06:31:14AM -0400, Masahiro Yamada wrote:
> 2018-09-13 11:51 GMT-04:00 Geert Uytterhoeven <geert@linux-m68k.org>:
> > Hi Yamada-san,
> >
> > On Wed, Sep 12, 2018 at 3:02 AM Masahiro Yamada
> > <yamada.masahiro@socionext.com> wrote:
> >> 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
> >>          ...
> >
> > 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.

Any other comments on this? I'd like to get the series into linux-next 
soon.

There was one other problem 0-day reported when building with 
CONFIG_OF=n while setting CONFIG_OF_ALL_DTBS=y on the kernel command 
line. The problem is dtc is not built as setting options on the command 
line doesn't invoke kconfig select(s). This can be fixed by also 
adding CONFIG_DTC=y to the command line, always building dtc regardless 
of Kconfig, or making 'all' conditionally dependent on 'dtbs'. I've gone 
with the last option as that is how this problem was avoided before. 

So the hunk in question with the 2 fixes now looks like this:

@@ -1215,6 +1215,35 @@ kselftest-merge:
                $(srctree)/tools/testing/selftests/*/config
        +$(Q)$(MAKE) -f $(srctree)/Makefile olddefconfig
 
+# 
---------------------------------------------------------------------------
+# Devicetree files
+
+ifneq ($(wildcard $(srctree)/arch/$(SRCARCH)/boot/dts/),)
+dtstree := arch/$(SRCARCH)/boot/dts
+endif
+
+ifneq ($(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)
+
+ifdef CONFIG_OF_EARLY_FLATTREE
+all: dtbs
+endif
+
+endif
+
+PHONY += scripts_dtc
+scripts_dtc: scripts_basic
+       $(Q)$(MAKE) $(build)=scripts/dtc
+
 # 
---------------------------------------------------------------------------
 # Modules
Andreas Färber Sept. 28, 2018, 5:21 p.m. | #6
Hi Geert,

Am 13.09.18 um 17:51 schrieb Geert Uytterhoeven:
> On Wed, Sep 12, 2018 at 3:02 AM Masahiro Yamada
> <yamada.masahiro@socionext.com> wrote:
>> 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 ;-)

How would loading a DT overlay work on an ACPI platform? I.e., what
would it overlay against and how to practically load such a file?

I wonder whether that could be helpful for USB devices and serdev...

Cheers,
Andreas
Rob Herring Sept. 28, 2018, 6:41 p.m. | #7
On Fri, Sep 28, 2018 at 12:21 PM Andreas Färber <afaerber@suse.de> wrote:
>
> Hi Geert,
>
> Am 13.09.18 um 17:51 schrieb Geert Uytterhoeven:
> > On Wed, Sep 12, 2018 at 3:02 AM Masahiro Yamada
> > <yamada.masahiro@socionext.com> wrote:
> >> 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 ;-)
>
> How would loading a DT overlay work on an ACPI platform? I.e., what
> would it overlay against and how to practically load such a file?

The DT unittests do just that. I run them on x86 and UM builds. In
this case, the loading source is built-in.

> I wonder whether that could be helpful for USB devices and serdev...

How to load the overlays is pretty orthogonal to the issues to be
solved here. It would certainly be possible to move forward with
prototyping this and just have the overlay built-in. It may not even
need to be an overlay if we can support multiple root nodes.

Rob
Masahiro Yamada Oct. 1, 2018, 5:49 a.m. | #8
Hi Rob,


2018年9月29日(土) 0:43 Rob Herring <robh@kernel.org>:

> +#
> ---------------------------------------------------------------------------
> +# Devicetree files
> +
> +ifneq ($(wildcard $(srctree)/arch/$(SRCARCH)/boot/dts/),)
> +dtstree := arch/$(SRCARCH)/boot/dts
> +endif
> +
> +ifneq ($(dtstree),)
> +
> +%.dtb : scripts_dtc

%.dtb: prepare3 prepare


because we need to make sure KERNELRELEASE
is correctly defined before dtbs_install happens.


> +       $(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
> +
> +PHONY += dtbs dtbs_install
> +dtbs: scripts_dtc


dtbs: prepare3 scripts_dtc



> +       $(Q)$(MAKE) $(build)=$(dtstree)
> +
> +dtbs_install: dtbs


Please do not have dtbs_install to depend on dtbs.

No install targets should ever trigger building anything
in the source tree.


For the background, see the commit log of
19514fc665ffbce624785f76ee7ad0ea6378a527




> +       $(Q)$(MAKE) $(dtbinst)=$(dtstree)
> +
> +ifdef CONFIG_OF_EARLY_FLATTREE
> +all: dtbs
> +endif
> +
> +endif
> +
> +PHONY += scripts_dtc
> +scripts_dtc: scripts_basic
> +       $(Q)$(MAKE) $(build)=scripts/dtc
> +
>  #
> ---------------------------------------------------------------------------
>  # Modules
>
Geert Uytterhoeven Oct. 1, 2018, 7:53 a.m. | #9
On Fri, Sep 28, 2018 at 8:42 PM Rob Herring <robh@kernel.org> wrote:
> On Fri, Sep 28, 2018 at 12:21 PM Andreas Färber <afaerber@suse.de> wrote:
> > Am 13.09.18 um 17:51 schrieb Geert Uytterhoeven:
> > > On Wed, Sep 12, 2018 at 3:02 AM Masahiro Yamada
> > > <yamada.masahiro@socionext.com> wrote:
> > >> 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 ;-)
> >
> > How would loading a DT overlay work on an ACPI platform? I.e., what
> > would it overlay against and how to practically load such a file?
>
> The DT unittests do just that. I run them on x86 and UM builds. In
> this case, the loading source is built-in.
>
> > I wonder whether that could be helpful for USB devices and serdev...
>
> How to load the overlays is pretty orthogonal to the issues to be
> solved here. It would certainly be possible to move forward with
> prototyping this and just have the overlay built-in. It may not even
> need to be an overlay if we can support multiple root nodes.

You indeed need to refer to some anchors for most use cases, although a
simple MMIO device could just be anchored to the root node.

Topologies hanging off a USB device would be my first use case, too,
for serdev, or for e.g. the mcp2210 USB-SPI bridge.

Gr{oetje,eeting}s,

                        Geert
Rob Herring Oct. 1, 2018, 1:25 p.m. | #10
On Mon, Oct 1, 2018 at 12:49 AM Masahiro Yamada
<yamada.masahiro@socionext.com> wrote:
>
> Hi Rob,
>
>
> 2018年9月29日(土) 0:43 Rob Herring <robh@kernel.org>:
>
> > +#
> > ---------------------------------------------------------------------------
> > +# Devicetree files
> > +
> > +ifneq ($(wildcard $(srctree)/arch/$(SRCARCH)/boot/dts/),)
> > +dtstree := arch/$(SRCARCH)/boot/dts
> > +endif
> > +
> > +ifneq ($(dtstree),)
> > +
> > +%.dtb : scripts_dtc
>
> %.dtb: prepare3 prepare

I assume you didn't mean to drop scripts_dtc as that doesn't work.

Why "prepare" here and not on dtbs?

> because we need to make sure KERNELRELEASE
> is correctly defined before dtbs_install happens.

Yes, indeed. With prepare3 added I get:

cp: cannot create regular file
'/boot/dtbs/4.19.0-rc3-00009-g0afba9b7b2ea-dirty': No such file or
directory

vs. with it:

cp: cannot create regular file '/boot/dtbs/': Not a directory

>
>
> > +       $(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
> > +
> > +PHONY += dtbs dtbs_install
> > +dtbs: scripts_dtc
>
>
> dtbs: prepare3 scripts_dtc
>
>
>
> > +       $(Q)$(MAKE) $(build)=$(dtstree)
> > +
> > +dtbs_install: dtbs
>
>
> Please do not have dtbs_install to depend on dtbs.
>
> No install targets should ever trigger building anything
> in the source tree.
>
>
> For the background, see the commit log of
> 19514fc665ffbce624785f76ee7ad0ea6378a527

Okay, thanks.

Rob
Masahiro Yamada Oct. 1, 2018, 2:48 p.m. | #11
Hi Rob,


2018年10月1日(月) 22:26 Rob Herring <robh@kernel.org>:
>
> On Mon, Oct 1, 2018 at 12:49 AM Masahiro Yamada
> <yamada.masahiro@socionext.com> wrote:
> >
> > Hi Rob,
> >
> >
> > 2018年9月29日(土) 0:43 Rob Herring <robh@kernel.org>:
> >
> > > +#
> > > ---------------------------------------------------------------------------
> > > +# Devicetree files
> > > +
> > > +ifneq ($(wildcard $(srctree)/arch/$(SRCARCH)/boot/dts/),)
> > > +dtstree := arch/$(SRCARCH)/boot/dts
> > > +endif
> > > +
> > > +ifneq ($(dtstree),)
> > > +
> > > +%.dtb : scripts_dtc
> >
> > %.dtb: prepare3 prepare
>
> I assume you didn't mean to drop scripts_dtc as that doesn't work.
>
> Why "prepare" here and not on dtbs?


Sorry, my mistake.


%.dtb: prepare3 scripts_dtc

is the correct one.



> > because we need to make sure KERNELRELEASE
> > is correctly defined before dtbs_install happens.
>
> Yes, indeed. With prepare3 added I get:
>
> cp: cannot create regular file
> '/boot/dtbs/4.19.0-rc3-00009-g0afba9b7b2ea-dirty': No such file or
> directory
>
> vs. with it:
>
> cp: cannot create regular file '/boot/dtbs/': Not a directory
>
> >
> >
> > > +       $(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@
> > > +
> > > +PHONY += dtbs dtbs_install
> > > +dtbs: scripts_dtc
> >
> >
> > dtbs: prepare3 scripts_dtc
> >
> >
> >
> > > +       $(Q)$(MAKE) $(build)=$(dtstree)
> > > +
> > > +dtbs_install: dtbs
> >
> >
> > Please do not have dtbs_install to depend on dtbs.
> >
> > No install targets should ever trigger building anything
> > in the source tree.
> >
> >
> > For the background, see the commit log of
> > 19514fc665ffbce624785f76ee7ad0ea6378a527
>
> Okay, thanks.
>
> Rob

Patch

diff --git a/Makefile b/Makefile
index 19948e556941..c43859eba70f 100644
--- a/Makefile
+++ b/Makefile
@@ -1071,7 +1071,7 @@  include/config/kernel.release: $(srctree)/Makefile FORCE
 # Carefully list dependencies so we do not try to build scripts twice
 # in parallel
 PHONY += scripts
-scripts: scripts_basic asm-generic gcc-plugins $(autoksyms_h)
+scripts: scripts_basic scripts_dtc asm-generic gcc-plugins $(autoksyms_h)
 	$(Q)$(MAKE) $(build)=$(@)
 
 # Things we need to do before we recursively start building the kernel
@@ -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
+
+%.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
+
+PHONY += scripts_dtc
+scripts_dtc: scripts_basic
+	$(Q)$(MAKE) $(build)=scripts/dtc
+
 # ---------------------------------------------------------------------------
 # Modules
 
@@ -1424,6 +1451,12 @@  help:
 	@echo  '  kselftest-merge - Merge all the config dependencies of kselftest to existing'
 	@echo  '                    .config.'
 	@echo  ''
+	@$(if $(dtstree), \
+		echo 'Devicetree:'; \
+		echo '* dtbs            - Build device tree blobs for enabled boards'; \
+		echo '  dtbs_install    - Install dtbs to $(INSTALL_DTBS_PATH)'; \
+		echo '')
+
 	@echo 'Userspace tools targets:'
 	@echo '  use "make tools/help"'
 	@echo '  or  "cd tools; make help"'
diff --git a/arch/arc/Makefile b/arch/arc/Makefile
index fb026196aaab..5c7bc6d62f43 100644
--- a/arch/arc/Makefile
+++ b/arch/arc/Makefile
@@ -132,11 +132,5 @@  boot_targets += uImage uImage.bin uImage.gz
 $(boot_targets): vmlinux
 	$(Q)$(MAKE) $(build)=$(boot) $(boot)/$@
 
-%.dtb %.dtb.S %.dtb.o: scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts $(boot)/dts/$@
-
-dtbs: scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts
-
 archclean:
 	$(Q)$(MAKE) $(clean)=$(boot)
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index d1516f85f25d..161c2df6567e 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -307,12 +307,7 @@  else
 KBUILD_IMAGE := $(boot)/zImage
 endif
 
-# Build the DT binary blobs if we have OF configured
-ifeq ($(CONFIG_USE_OF),y)
-KBUILD_DTBS := dtbs
-endif
-
-all:	$(notdir $(KBUILD_IMAGE)) $(KBUILD_DTBS)
+all:	$(notdir $(KBUILD_IMAGE))
 
 
 archheaders:
@@ -339,17 +334,6 @@  $(BOOT_TARGETS): vmlinux
 $(INSTALL_TARGETS):
 	$(Q)$(MAKE) $(build)=$(boot) MACHINE=$(MACHINE) $@
 
-%.dtb: | scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts MACHINE=$(MACHINE) $(boot)/dts/$@
-
-PHONY += dtbs dtbs_install
-
-dtbs: prepare scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts
-
-dtbs_install:
-	$(Q)$(MAKE) $(dtbinst)=$(boot)/dts
-
 PHONY += vdso_install
 vdso_install:
 ifeq ($(CONFIG_VDSO),y)
@@ -371,8 +355,6 @@  define archhelp
   echo  '  uImage        - U-Boot wrapped zImage'
   echo  '  bootpImage    - Combined zImage and initial RAM disk'
   echo  '                  (supply initrd image via make variable INITRD=<path>)'
-  echo  '* dtbs          - Build device tree blobs for enabled boards'
-  echo  '  dtbs_install  - Install dtbs to $(INSTALL_DTBS_PATH)'
   echo  '  install       - Install uncompressed kernel'
   echo  '  zinstall      - Install compressed kernel'
   echo  '  uinstall      - Install U-Boot wrapped compressed kernel'
diff --git a/arch/arm64/Makefile b/arch/arm64/Makefile
index 106039d25e2f..b4e994cd3a42 100644
--- a/arch/arm64/Makefile
+++ b/arch/arm64/Makefile
@@ -113,9 +113,8 @@  core-$(CONFIG_EFI_STUB) += $(objtree)/drivers/firmware/efi/libstub/lib.a
 # Default target when executing plain make
 boot		:= arch/arm64/boot
 KBUILD_IMAGE	:= $(boot)/Image.gz
-KBUILD_DTBS	:= dtbs
 
-all:	Image.gz $(KBUILD_DTBS)
+all:	Image.gz
 
 
 Image: vmlinux
@@ -127,17 +126,6 @@  Image.%: Image
 zinstall install:
 	$(Q)$(MAKE) $(build)=$(boot) $@
 
-%.dtb: scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts $(boot)/dts/$@
-
-PHONY += dtbs dtbs_install
-
-dtbs: prepare scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts
-
-dtbs_install:
-	$(Q)$(MAKE) $(dtbinst)=$(boot)/dts
-
 PHONY += vdso_install
 vdso_install:
 	$(Q)$(MAKE) $(build)=arch/arm64/kernel/vdso $@
@@ -145,7 +133,6 @@  vdso_install:
 # We use MRPROPER_FILES and CLEAN_FILES now
 archclean:
 	$(Q)$(MAKE) $(clean)=$(boot)
-	$(Q)$(MAKE) $(clean)=$(boot)/dts
 
 # We need to generate vdso-offsets.h before compiling certain files in kernel/.
 # In order to do that, we should use the archprepare target, but we can't since
@@ -160,8 +147,6 @@  vdso_prepare: prepare0
 define archhelp
   echo  '* Image.gz      - Compressed kernel image (arch/$(ARCH)/boot/Image.gz)'
   echo  '  Image         - Uncompressed kernel image (arch/$(ARCH)/boot/Image)'
-  echo  '* dtbs          - Build device tree blobs for enabled boards'
-  echo  '  dtbs_install  - Install dtbs to $(INSTALL_DTBS_PATH)'
   echo  '  install       - Install uncompressed kernel'
   echo  '  zinstall      - Install compressed kernel'
   echo  '                  Install using (your) ~/bin/installkernel or'
diff --git a/arch/c6x/Makefile b/arch/c6x/Makefile
index 3fe8a948e94c..b7aa854f7008 100644
--- a/arch/c6x/Makefile
+++ b/arch/c6x/Makefile
@@ -40,9 +40,7 @@  boot := arch/$(ARCH)/boot
 DTB:=$(subst dtbImage.,,$(filter dtbImage.%, $(MAKECMDGOALS)))
 export DTB
 
-ifneq ($(DTB),)
 core-y	+= $(boot)/dts/
-endif
 
 # With make 3.82 we cannot mix normal and wildcard targets
 
diff --git a/arch/h8300/Makefile b/arch/h8300/Makefile
index 58634e6bae92..4003ddc616e1 100644
--- a/arch/h8300/Makefile
+++ b/arch/h8300/Makefile
@@ -31,21 +31,12 @@  CROSS_COMPILE := h8300-unknown-linux-
 endif
 
 core-y	+= arch/$(ARCH)/kernel/ arch/$(ARCH)/mm/
-ifneq '$(CONFIG_H8300_BUILTIN_DTB)' '""'
-core-y += arch/h8300/boot/dts/
-endif
+core-y	+= arch/$(ARCH)/boot/dts/
 
 libs-y	+= arch/$(ARCH)/lib/
 
 boot := arch/h8300/boot
 
-%.dtb %.dtb.S %.dtb.o: | scripts
-	$(Q)$(MAKE) $(build)=arch/h8300/boot/dts arch/h8300/boot/dts/$@
-
-PHONY += dtbs
-dtbs: scripts
-	$(Q)$(MAKE) $(build)=arch/h8300/boot/dts
-
 archmrproper:
 
 archclean:
diff --git a/arch/microblaze/Makefile b/arch/microblaze/Makefile
index 4f3ab5707265..0823d291fbeb 100644
--- a/arch/microblaze/Makefile
+++ b/arch/microblaze/Makefile
@@ -65,9 +65,7 @@  boot := arch/microblaze/boot
 # Are we making a simpleImage.<boardname> target? If so, crack out the boardname
 DTB:=$(subst simpleImage.,,$(filter simpleImage.%, $(MAKECMDGOALS)))
 
-ifneq ($(DTB),)
-	core-y	+= $(boot)/dts/
-endif
+core-y	+= $(boot)/dts/
 
 # defines filename extension depending memory management type
 ifeq ($(CONFIG_MMU),)
diff --git a/arch/microblaze/boot/dts/Makefile b/arch/microblaze/boot/dts/Makefile
index 1f77913d404d..fe9af267f598 100644
--- a/arch/microblaze/boot/dts/Makefile
+++ b/arch/microblaze/boot/dts/Makefile
@@ -1,6 +1,7 @@ 
 # SPDX-License-Identifier: GPL-2.0
 #
 
+ifneq ($(DTB),)
 obj-y += linked_dtb.o
 
 # Ensure system.dtb exists
@@ -11,6 +12,7 @@  ifneq ($(DTB),system)
 $(obj)/system.dtb: $(obj)/$(DTB).dtb
 	$(call if_changed,cp)
 endif
+endif
 
 quiet_cmd_cp = CP      $< $@$2
 	cmd_cp = cat $< >$@$2 || (rm -f $@ && echo false)
diff --git a/arch/mips/Makefile b/arch/mips/Makefile
index d74b3742fa5d..d43eeaa6d75b 100644
--- a/arch/mips/Makefile
+++ b/arch/mips/Makefile
@@ -407,18 +407,7 @@  endif
 CLEAN_FILES += vmlinux.32 vmlinux.64
 
 # device-trees
-core-$(CONFIG_BUILTIN_DTB) += arch/mips/boot/dts/
-
-%.dtb %.dtb.S %.dtb.o: | scripts
-	$(Q)$(MAKE) $(build)=arch/mips/boot/dts arch/mips/boot/dts/$@
-
-PHONY += dtbs
-dtbs: scripts
-	$(Q)$(MAKE) $(build)=arch/mips/boot/dts
-
-PHONY += dtbs_install
-dtbs_install:
-	$(Q)$(MAKE) $(dtbinst)=arch/mips/boot/dts
+core-y += arch/mips/boot/dts/
 
 archprepare:
 ifdef CONFIG_MIPS32_N32
@@ -461,8 +450,6 @@  define archhelp
 	echo '  uImage.lzma          - U-Boot image (lzma)'
 	echo '  uImage.lzo           - U-Boot image (lzo)'
 	echo '  uzImage.bin          - U-Boot image (self-extracting)'
-	echo '  dtbs                 - Device-tree blobs for enabled boards'
-	echo '  dtbs_install         - Install dtbs to $(INSTALL_DTBS_PATH)'
 	echo
 	echo '  These will be default as appropriate for a configured platform.'
 	echo
diff --git a/arch/nds32/Makefile b/arch/nds32/Makefile
index 63f4f173e5f4..adcac830d051 100644
--- a/arch/nds32/Makefile
+++ b/arch/nds32/Makefile
@@ -43,7 +43,7 @@  CHECKFLAGS      += -D__NDS32_EB__
 endif
 
 boot := arch/nds32/boot
-core-$(BUILTIN_DTB) += $(boot)/dts/
+core-y += $(boot)/dts/
 
 .PHONY: FORCE
 
diff --git a/arch/nios2/Makefile b/arch/nios2/Makefile
index db2e78fe65c7..52c03e60b114 100644
--- a/arch/nios2/Makefile
+++ b/arch/nios2/Makefile
@@ -56,12 +56,6 @@  all: vmImage
 archclean:
 	$(Q)$(MAKE) $(clean)=$(nios2-boot)
 
-%.dtb %.dtb.S %.dtb.o: | scripts
-	$(Q)$(MAKE) $(build)=$(nios2-boot)/dts $(nios2-boot)/dts/$@
-
-dtbs:
-	$(Q)$(MAKE) $(build)=$(nios2-boot)/dts
-
 $(BOOT_TARGETS): vmlinux
 	$(Q)$(MAKE) $(build)=$(nios2-boot) $(nios2-boot)/$@
 
@@ -74,5 +68,4 @@  define archhelp
   echo  '                     (your) ~/bin/$(INSTALLKERNEL) or'
   echo  '                     (distribution) /sbin/$(INSTALLKERNEL) or'
   echo  '                     install to $$(INSTALL_PATH)'
-  echo  '  dtbs            - Build device tree blobs for enabled boards'
 endef
diff --git a/arch/nios2/boot/Makefile b/arch/nios2/boot/Makefile
index 0b48f1bf086d..37dfc7e584bc 100644
--- a/arch/nios2/boot/Makefile
+++ b/arch/nios2/boot/Makefile
@@ -31,9 +31,5 @@  $(obj)/zImage: $(obj)/compressed/vmlinux FORCE
 $(obj)/compressed/vmlinux: $(obj)/vmlinux.gz FORCE
 	$(Q)$(MAKE) $(build)=$(obj)/compressed $@
 
-targets += $(dtb-y)
-
-$(obj)/dtbs: $(addprefix $(obj)/, $(dtb-y))
-
 install:
 	sh $(srctree)/$(src)/install.sh $(KERNELRELEASE) $(BOOTIMAGE) System.map "$(INSTALL_PATH)"
diff --git a/arch/powerpc/Makefile b/arch/powerpc/Makefile
index 53ea887eb34e..42f225f6ec93 100644
--- a/arch/powerpc/Makefile
+++ b/arch/powerpc/Makefile
@@ -293,9 +293,6 @@  $(BOOT_TARGETS2): vmlinux
 bootwrapper_install:
 	$(Q)$(MAKE) $(build)=$(boot) $(patsubst %,$(boot)/%,$@)
 
-%.dtb: scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts $(patsubst %,$(boot)/dts/%,$@)
-
 # Used to create 'merged defconfigs'
 # To use it $(call) it with the first argument as the base defconfig
 # and the second argument as a space separated list of .config files to merge,
diff --git a/arch/xtensa/Makefile b/arch/xtensa/Makefile
index 295c120ed099..13fd3301c517 100644
--- a/arch/xtensa/Makefile
+++ b/arch/xtensa/Makefile
@@ -84,28 +84,18 @@  LIBGCC := $(shell $(CC) $(KBUILD_CFLAGS) -print-libgcc-file-name)
 head-y		:= arch/xtensa/kernel/head.o
 core-y		+= arch/xtensa/kernel/ arch/xtensa/mm/
 core-y		+= $(buildvar) $(buildplf)
+core-y 		+= arch/xtensa/boot/dts/
 
 libs-y		+= arch/xtensa/lib/ $(LIBGCC)
 drivers-$(CONFIG_OPROFILE)	+= arch/xtensa/oprofile/
 
-ifneq ($(CONFIG_BUILTIN_DTB),"")
-core-$(CONFIG_OF) += arch/xtensa/boot/dts/
-endif
-
 boot		:= arch/xtensa/boot
 
 all Image zImage uImage: vmlinux
 	$(Q)$(MAKE) $(build)=$(boot) $@
 
-%.dtb:
-	$(Q)$(MAKE) $(build)=$(boot)/dts $(boot)/dts/$@
-
-dtbs: scripts
-	$(Q)$(MAKE) $(build)=$(boot)/dts
-
 define archhelp
   @echo '* Image       - Kernel ELF image with reset vector'
   @echo '* zImage      - Compressed kernel image (arch/xtensa/boot/images/zImage.*)'
   @echo '* uImage      - U-Boot wrapped image'
-  @echo '  dtbs        - Build device tree blobs for enabled boards'
 endef
diff --git a/scripts/Makefile b/scripts/Makefile
index 61affa300d25..ece52ff20171 100644
--- a/scripts/Makefile
+++ b/scripts/Makefile
@@ -39,8 +39,7 @@  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
-subdir-	+= basic kconfig package gcc-plugins
+subdir-	+= basic dtc kconfig package gcc-plugins
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 61e596650ed3..8fe4468f9bda 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -283,7 +283,7 @@  $(obj)/%.dtb.S: $(obj)/%.dtb FORCE
 
 quiet_cmd_dtc = DTC     $@
 cmd_dtc = mkdir -p $(dir ${dtc-tmp}) ; \
-	$(CPP) $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
+	$(HOSTCC) -E $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) $< ; \
 	$(DTC) -O dtb -o $@ -b 0 \
 		$(addprefix -i,$(dir $<) $(DTC_INCLUDE)) $(DTC_FLAGS) \
 		-d $(depfile).dtc.tmp $(dtc-tmp) ; \
diff --git a/scripts/dtc/Makefile b/scripts/dtc/Makefile
index 1c943e03eaf2..e535b457babb 100644
--- a/scripts/dtc/Makefile
+++ b/scripts/dtc/Makefile
@@ -1,7 +1,7 @@ 
 # SPDX-License-Identifier: GPL-2.0
 # scripts/dtc makefile
 
-hostprogs-y	:= dtc
+hostprogs-$(CONFIG_DTC) := dtc
 always		:= $(hostprogs-y)
 
 dtc-objs	:= dtc.o flattree.o fstree.o data.o livetree.o treesource.o \