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From: Segher Boessenkool <segher@kernel.crashing.org>
Subject: Re: [patch 00/13] CPU selection Kconfig cleanup, take 3
Date: Sun, 17 Jun 2007 02:19:36 +0200
To: Kumar Gala <galak@kernel.crashing.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>, arnd@arndb.de,
	linuxppc-dev@ozlabs.org, Paul Mackerras <paulus@samba.org>,
	Sam Ravnborg <sam@ravnborg.org>
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>> I would much
>> prefer the CONFIG_xxx_ONLY_ONE be -generated- by the multiple choice
>> menu if only one choice has been selected.
>>
>> That could be an optional argument to the menu stuff to set that.
>
> That was my intent, that the Kconfig system would help in telling us
> only one choice was selected and we could optimize based on that.  In
> addition, to ensure that at least one choice was selected.  I believe
> Rob Landley came across an issue that exists today with MULTIPLATFORM
> support in that we can attempt to build a kernel w/o any system.

Each of the CPU options is set to either "y" or "", so:


options-$(option1)$(option2)$(option3) := y

ifeq ($(options)-,y)
	$(error blablabla)
endif

CONFIG_POWERPC_ONLY_ONE_CPU := $(options-y)


or some variant on this will do just fine.


Segher