[RFC, 1/2] scripts/kconfig/Makefile: Allow KBUILD_DEFCONFIG to be a target

[Olof Johansson]

On Tue, Oct 13, 2015 at 4:43 PM, Michael Ellerman <mpe at ellerman.id.au> wrote:
> On Tue, 2015-10-13 at 14:02 -0700, Olof Johansson wrote:
>> On Fri, Oct 2, 2015 at 12:47 AM, Michael Ellerman <mpe at ellerman.id.au> wrote:
>> > On Wed, 2015-23-09 at 05:40:34 UTC, Michael Ellerman wrote:
>> >> Arch Makefiles can set KBUILD_DEFCONFIG to tell kbuild the name of the
>> >> defconfig that should be built by default.
>> >>
>> >> However currently there is an assumption that KBUILD_DEFCONFIG points to
>> >> a file at arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG).
>> >>
>> >> We would like to use a target, using merge_config, as our defconfig, so
>> >> adapt the logic in scripts/kconfig/Makefile to allow that.
>> >>
>> >> To minimise the chance of breaking anything, we first check if
>> >> KBUILD_DEFCONFIG is a file, and if so we do the old logic. If it's not a
>> >> file, then we call the top-level Makefile with KBUILD_DEFCONFIG as the
>> >> target.
>> >>
>> >> Signed-off-by: Michael Ellerman <mpe at ellerman.id.au>
>> >> Acked-by: Michal Marek <mmarek at suse.com>
>> >
>> > Applied to powerpc next.
>> >
>> > https://git.kernel.org/powerpc/c/d2036f30cfe1daa19e63ce75
>>
>> This breaks arm64 defconfig for me:
>>
>> mkdir obj-tmp
>> make -f Makefile O=obj-tmp ARCH=arm64 defconfig
>> ... watch loop of:
>> *** Default configuration is based on target 'defconfig'
>>   GEN     ./Makefile
>
> Crap, sorry. I knew I shouldn't have touched that code!
>
> Does this fix it for you?

Yes, it does, however:

>
> diff --git a/scripts/kconfig/Makefile b/scripts/kconfig/Makefile
> index b2b9c87..3043d6b 100644
> --- a/scripts/kconfig/Makefile
> +++ b/scripts/kconfig/Makefile
> @@ -96,7 +96,7 @@ savedefconfig: $(obj)/conf
>  defconfig: $(obj)/conf
>  ifeq ($(KBUILD_DEFCONFIG),)
>         $< $(silent) --defconfig $(Kconfig)
> -else ifneq ($(wildcard arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)),)
> +else ifneq ($(wildcard $(srctree)/arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG)),)
>         @$(kecho) "*** Default configuration is based on '$(KBUILD_DEFCONFIG)'"
>         $(Q)$< $(silent) --defconfig=arch/$(SRCARCH)/configs/$(KBUILD_DEFCONFIG) $(Kconfig)

Do you need a $(srctree) prefix here too? I'm not entirely sure what I
would do to reproduce a run that goes down this path so I can't
confirm.


-Olof