Re: kconfig/build question..

[Adrian Bunk <bunk@stusta.de>]

On Wed, Nov 10, 2004 at 01:16:10AM +0000, Dave Airlie wrote:
> 
> I've come across something that I'm not sure Kconfig can do but I'll
> explain what I need and see what others can come up with...
> 
> The DRM has a weak dependency on AGP, it does not require AGP for all
> situations but can use it in most...
> 
> So what I want to do and what I think Kbuild can't do is:
> 
> if CONFIG_AGP=n then CONFIG_DRM can be n,m,y
> if CONFIG_AGP=m then CONFIG_DRM can be m but not y
> if CONFIG_AGP=y then CONFIG_DRM can be m,y
>...

The second case is bad because enabling a module shouldn't change the 
static parts of the kernel [1].

Let me suggest a slightly different solution:

I assume a "weak dependency" dependency means you can enable some AGP 
specific code in the DRM code?

config DRM_AGP
	bool
	depends on ((DRM = "m" && AGP) || (DRM = "y" && AGP = "y"))
	default y

In the DRM code, you #ifdef CONFIG_DRM_AGP the AGP specific code.

This way, CONFIG_AGP=m and CONFIG_DRM=y is a legal configuration but 
doesn't enable the AGP specific code in the DRM code.

> Dave.

cu
Adrian

[1] yes, this isn't always true in the current kernel

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