On Mon, Sep 29, 2014 at 01:49:22PM +0100, Grant Likely wrote:

On Fri, 26 Sep 2014 10:19:43 -0400
, Jason Cooper [off-list ref]
 wrote:

quoted

Linus,

On Fri, Sep 26, 2014 at 02:30:53PM +0200, Linus Walleij wrote:

quoted

On Tue, Apr 1, 2014 at 12:15 PM, Grant Likely [off-list ref] wrote:

quoted

Here are the dt changes I've got queued up for v3.15. The full
description is below in the tag. Please pull.

(...)

quoted

Jason Cooper (1):
      kbuild: dtbs_install: new make target

Exact patch is:

  f4d4ffc03efc kbuild: dtbs_install: new make target

quoted

After this patch a while back I have observed the following behaviour
of the kernel build:

make zImage
make zImage
-> incremental build, just relink

make zImage
make dtbs
make zImage
-> The whole kernel gets rebuilt

So now if I happen to recompile my device trees, I suddenly want
the entire zImage to be rebuilt to? It's by definition not changes that
affect the kernel build :-(

I noticed this because my build scripts calls make dtbs && make zImage,
and started to rebuild absolutely everything all the time.

Do you think this can be fixed? It's quite simple to reproduce...

Does the attached fix your problem?

thx,

Jason.

----------->8------------------------------------------

diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 0ce9d0f71f2a..a88b13af58d2 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile

@@ -313,7 +313,9 @@ $(INSTALL_TARGETS):
 	$(Q)$(MAKE) $(build)=$(boot)/dts MACHINE=$(MACHINE) $(boot)/dts/$@
 
 PHONY += dtbs dtbs_install
-dtbs dtbs_install: prepare scripts
+dtbs: scripts
+	$(Q)$(MAKE) $(build)=$(boot)/dts MACHINE=$(MACHINE) $@
+dtbs_install: prepare scripts
 	$(Q)$(MAKE) $(build)=$(boot)/dts MACHINE=$(MACHINE) $@
 
 # We use MRPROPER_FILES and CLEAN_FILES now

Is this the right fix though? It seems that it would fix the problem for
the dtbs target, but would still cause a kernel rebuild for
dtbs_install. Why does dtbs_install need to depend on the 'prepare'
target?

iirc, it was added as a dependency to ensure $KERNELVERSION was set
before attempting to install into /path/to/$KERNELVERSION/dtbs.

This patch was just a confirmation that the 'prepare' target was the
source of the problem for Linus.  Now that we know that, we need to dig
and find a proper fix for setting $KERNELVERSION for dtbs_install.

I dug into the prepare* menagerie a bit preparing this test patch, and
it seems that any existing target which would get us $KERNELVERSION also
depends on FORCE.  I haven't had time to dig into it more... Perhaps one
of the kbuild maintainers would have some insight?

thx,

Jason.
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