linux-kernel - Re: kbuild now support arch/$ARCH/include

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Message-ID: <20080731201352.GB25305@uranus.ravnborg.org>
Date:	Thu, 31 Jul 2008 22:13:52 +0200
From:	Sam Ravnborg <sam@...nborg.org>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Paul Mundt <lethal@...ux-sh.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	David Howells <dhowells@...hat.com>,
	Greg Ungerer <gerg@...pgear.com>,
	linux arch <linux-arch@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Linux/m68k <linux-m68k@...r.kernel.org>,
	uClinux list <uclinux-dev@...inux.org>
Subject: Re: kbuild now support arch/$ARCH/include - time for ARCHs to convert

On Thu, Jul 31, 2008 at 09:47:25PM +0200, Arnd Bergmann wrote:
> On Thursday 31 July 2008, Paul Mundt wrote:
> > This sort of merging is fairly easy to do incrementally, at least by
> > someone that has both platforms available. An easy first step would be to
> > move the m68knommu stuff that are implemented differently over as _nommu
> > files, similar to how the _32/_64 renames happened, and then set about
> > converging the two little by little. This is what I've been doing with
> > sh64->sh integration for example, despite fundamental differences like
> > having a totally different register layout and instruction set.
>  
> I've played around with the purely mechanical side of merging the
> m68k{,nommu} header files and came up with a script to do it.
> All headers that are identical are used from their m68k variant, the
> others get an #include magic like x86 has it for 32/64.
> 
> This assumes that the kernel ABI is compatible and that user space
> can actually use the m68k headers for m68knommu as well.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>
> ---
> TARGET=arch/m68k/include/asm
> SOURCE1=include/asm-m68k
> SOURCE2=include/asm-m68knommu
> FILES="atomic.h bitops.h bootinfo.h bug.h bugs.h byteorder.h cache.h \
> cacheflush.h checksum.h cputime.h current.h delay.h div64.h \
> dma-mapping.h dma.h elf.h entry.h fb.h fpu.h hardirq.h hw_irq.h io.h \
> irq.h kmap_types.h local.h machdep.h mc146818rtc.h mmu.h mmu_context.h \
> module.h page.h page_offset.h param.h pci.h percpu.h pgalloc.h \
> pgtable.h processor.h ptrace.h scatterlist.h sections.h segment.h \
> setup.h sigcontext.h siginfo.h signal.h string.h system.h \
> thread_info.h timex.h tlbflush.h traps.h uaccess.h ucontext.h \
> unaligned.h unistd.h"
> EXPORTS="byteorder param ptrace sigcontext siginfo signal unistd"
> 
> mergefile() {
> 	BASE=${1%.h}
> 	mv $SOURCE1/$1 $TARGET/${BASE}_mmu.h
> 	mv $SOURCE2/$1 $TARGET/${BASE}_nommu.h
> cat << EOF > $TARGET/$1
> #ifdef __KERNEL__
> #ifdef CONFIG_MMU
> #include "${BASE}_mmu.h"
> #else
> #include "${BASE}_nommu.h"
> #endif
> #else
> #include "${BASE}_mmu.h"
> #endif
> EOF
> }

This will leak a CONFIG_ symbol if the header file
is exported. Can we do it with a gcc defined symbol?
[See how I did it for sparc for instance]

> 
> mergefile2() {
> 	if [ -e ${TARGET}/$1 ] ; then
> 		rm $SOURCE2/$1
> 	else
> 		mv $SOURCE2/$1 ${TARGET}
> 	fi
> }
> 
> addexport() {
> 	echo "unifdef-y += ${1}_mmu.h" >> $TARGET/Kbuild
> }
unifdef is deprecated. Plese use "header-y".
They have same effect these days.

	Sam
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