Date: Mon, 7 Sep 2009 15:09:04 +0200
From: Pavel Machek <pavel@ucw.cz>
To: Roland McGrath <roland@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
       Sam Ravnborg <sam@ravnborg.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] kconfig CROSS_COMPILE option
Message-ID: <20090907130402.GB1595@ucw.cz>
References: <20090905002947.A4C678BEB1@magilla.sf.frob.com>
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Hi!

> This adds CROSS_COMPILE as a kconfig string so you can store it in .config.
> Then you can use plain "make" in the configured kernel build directory to
> do the right cross compilation without setting the command-line or
> environment variable every time.
> 
> With this, you can set up different build directories for different kernel
> configurations, whether native or cross-builds, and then use the simple:
> 	make -C /build/dir M=module-source-dir
> idiom to build modules for any given target kernel, indicating which one
> by nothing but the build directory chosen.
> 
> I tried a version that defaults the string with env="CROSS_COMPILE" so that
> in a "make oldconfig" with CROSS_COMPILE in the environment you can just
> hit return to store the way you're building it.  But the kconfig prompt for
> strings doesn't give you any way to say you want an empty string instead of
> the default, so I punted that.

Yes that would be very nice. Editing Makefile every time I
crosscomppile for arm sucks.

But... do we need an option for subarch, too? And will Kconfig system
handle that?
									Pavel

>  # Alternatively CROSS_COMPILE can be set in the environment.
> +# A third alternative is to store a setting in .config so that plain
> +# "make" in the configured kernel build directory always uses that.
>  # Default value for CROSS_COMPILE is not to prefix executables
>  # Note: Some architectures assign CROSS_COMPILE in their arch/*/Makefile
>  export KBUILD_BUILDHOST := $(SUBARCH)
>  ARCH		?= $(SUBARCH)
> -CROSS_COMPILE	?=
> +CROSS_COMPILE	?= $(CONFIG_CROSS_COMPILE:"%"=%)
>  
>  # Architecture as present in compile.h
>  UTS_MACHINE 	:= $(ARCH)
> diff --git a/init/Kconfig b/init/Kconfig
> index 3f7e609..452080d 100644

-- 
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(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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