[U-Boot] [PATCH] kbuild,tegra124: add dummy obj- for Kbuild

[Stephen Warren <swarren@wwwdotorg.org>]

On 02/21/2014 04:45 AM, Masahiro Yamada wrote:
> On Thu, 20 Feb 2014 09:15:21 -0700 Stephen Warren  wrote:
>> On 02/20/2014 01:24 AM, Masahiro Yamada wrote:
>>> On Wed, 19 Feb 2014 09:36:14 -0700 Stephen Warren wrote:
>>>> On 02/19/2014 07:46 AM, Albert ARIBAUD wrote:
>>>>> On Wed, 19 Feb 2014 22:26:43 +0900, Masahiro wrote:
>>>>>
>>>>>> In Kbuild, every makefile must have non-empty obj- or obj-y.
>>>>>> Otherwise, built-in.o will not be created and the link stage
>>>>>> will fail.
>>>> ...
>>>>>> diff --git a/arch/arm/cpu/armv7/tegra124/Makefile b/arch/arm/cpu/armv7/tegra124/Makefile
>>>> ...
>>>>>> +# necessary to create built-in.o
>>>>>> +obj- := __dummy__.o
>>>>
>>>> obj- or obj-y?
>>>
>>> Definitely obj-.
>>
>> Really? Why would such a variable even exist or be used. Only obj-n or
>> obj-y should exist; "" isn't a valid y/n value.
> 
> All defined CONFIG macros are included in
> include/autoconf.mk  (and include/spl-autoconf.mk,
> include/tpl-autoconf.mk  for SPL, TPL, respectively)
> 
> If CONFIG_FOO is defined in your  config header, 
> CONFIG_FOO=y  will apear in include/autoconf.mk
> Otherwise, it does not appear in include/autoconf.mk.
...
> Is this clearer now?

OK, that makes sense.

I would have expected that Kbuild could detect obj-y is empty, and skip
building builtin.o, and skip attempting to link it in to the parent
directory too. However, if it doesn't do that, then this all makes
sense. Thanks.