[U-Boot] [RFC PATCH 2/2] linux/kconfig.h: add C macros useful for per-image config options

[Tom Rini]

On Thu, Jul 23, 2015 at 08:31:56PM +0900, Masahiro Yamada wrote:

> The previous commit introduced a useful macro used in makefiles,
> which references to different variables (CONFIG_ or CONFIG_SPL_
> prefixed), in order to enable/disable features independently
> for each of images.
> 
> Per-image config option control is a PITA in C sources, too.
> So, introduce some macros useful in C/CPP expressions.
> 
> CONFIG_IS_ENABLED(FOO) is a shorthand for
> 
>   (!defined(CONFIG_SPL_BUILD) && defined(CONFIG_FOO)) || \
>    (defined(CONFIG_SPL_BUILD) && defined(CONFIG_SPL_FOO))
> 
> For example, it is useful to describe C code as follows,
> 
>   #if CONFIG_IS_ENABLED(OF_CONTROL)
>       (device tree code)
>   #else
>       (board file code)
>   #endif
> 
> The ifdef conditional above is switched by CONFIG_OF_CONTROL during
> the U-Boot proper building (CONFIG_SPL_BUILD is not defined), and by
> CONFIG_SPL_OF_CONTROL during SPL building (CONFIG_SPL_BUILD is
> defined).
> 
> The macro can be used in C context as well, so you can also write the
> equivalent code as follows:
> 
>   if (CONFIG_IS_ENABLED(OF_CONTROL)) {
>       (device tree code)
>   } else {
>       (board file code)
>   }
> 
> Another useful macro is CONFIG_VALUE().
> CONFIG_VALUE(FOO) is expanded into CONFIG_FOO during the main build,
> and into CONFIG_SPL_FOO during SPL build.
> 
> You can write as follows:
> 
>   text_base = CONFIG_VALUE(TEXT_BASE);
> 
> instead of:
> 
>   #ifdef CONFIG_SPL_BUILD
>       text_base = CONFIG_SPL_TEXT_BASE;
>   #else
>       text_base = CONFIG_TEXT_BASE;
>   #endif
> 
> Signed-off-by: Masahiro Yamada <yamada.masahiro at socionext.com>

Reviewed-by: Tom Rini <trini at konsulko.com>

-- 
Tom
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