2018-08-27 8:56 GMT+09:00 Rob Herring [off-list ref]:

On Sat, Aug 25, 2018 at 9:06 PM Masahiro Yamada
[off-list ref] wrote:

quoted

Hi Rob,


2018-08-22 6:55 GMT+09:00 Rob Herring [off-list ref]:

quoted

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 <redacted>
Cc: Michal Marek <redacted>
Cc: Vineet Gupta <redacted>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <redacted>
Cc: Yoshinori Sato <ysato@users.sourceforge.jp>
Cc: Michal Simek <monstr@monstr.eu>
Cc: Ralf Baechle <redacted>
Cc: Paul Burton <redacted>
Cc: James Hogan <jhogan@kernel.org>
Cc: Ley Foon Tan <redacted>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <redacted>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@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@kernel.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

quoted

quoted

+
+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?

Yes.

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?

The pipe is used when

  - we want to make sure the weaker prerequisite exists

  - but, we do not want to execute the recipe
    even if the weaker prerequisite is updated


In this case, we want to execute the recipe _all_the_time_.

We compare the timestamp between %.dtb and %.dts in the sub-directory.

We never know the real depenency until the following recipe is run
     $(Q)$(MAKE) $(build)=$(dtstree) $(dtstree)/$@



PHONY += dtbs
dtbs: | dtc
      $(Q)$(MAKE) $(build)=$(dtstree)

Here 'dtbs' is a PHONY target.
We always want to run the recipe.
The pipe operator is not sensible.


-- 
Best Regards
Masahiro Yamada