Re: [v4l-dvb-maintainer] 2.6.25 regression: VIDEO_DEV=y/m, I2C=n compile error

[Trent Piepho <xyzzy@speakeasy.org>]

On Mon, 28 Jan 2008, Jan Engelhardt wrote:
> On Jan 28 2008 01:05, Trent Piepho wrote:
>
> >Maybe the kernel headers should provide a couple macros for testing
> >configs, since people get it wrong over and over again?
> >
> >#define CONFIG_ON(x) (defined(CONFIG_##x) || defined(CONFIG_##x##_MODULE))
> >#define CONFIG_AVAIABLE(x) (defined(CONFIG_##x) || (defined(MODULE) && defined(CONFIG_##x##_MODULE)))
>                ^AVAILABLE(x)
>
> What's the difference between these two?
>
> CONFIG_x_MODULE will never be defined if MODULE is not, so defined(MODULE)
> seems redundant.

You're probably thinking of CONFIG_MODULES, which indicates the kernel
supports module loading.  MODULE indicates the current code is being
compiled as a module.  The idea is that code compiled in the kernel can't
call modules.  Generally what you would see is:

#if CONFIG_ON(x)
code that will be _used by_ x
probably want x to depend on us in Kconfig
#endif
#if CONFIG_AVAILABLE(x)
code that wants _to use_ x
#endif