From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753783Ab1IGTeh (ORCPT ); Wed, 7 Sep 2011 15:34:37 -0400 Received: from mail-pz0-f42.google.com ([209.85.210.42]:58004 "EHLO mail-pz0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751121Ab1IGTeg convert rfc822-to-8bit (ORCPT ); Wed, 7 Sep 2011 15:34:36 -0400 MIME-Version: 1.0 In-Reply-To: References: <1313800642-32418-1-git-send-email-lacombar@gmail.com> Date: Wed, 7 Sep 2011 15:34:35 -0400 Message-ID: Subject: Re: [RFC] Kbuild: allow code re-use across different directories From: Arnaud Lacombe To: Nicolas Pitre Cc: linux-kbuild@vger.kernel.org, linux-arm-kernel@lists.infradead.org, lkml Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On Wed, Sep 7, 2011 at 3:07 PM, Nicolas Pitre wrote: > On Fri, 19 Aug 2011, Arnaud Lacombe wrote: > >> Hi folks, >> >> The attached patch modify Kbuild to allow to directly re-use code in multiple >> directory without having to go through a copy. Technically, it changes Kbuild to >> use by default the VPATH feature of GNU make and provides accessors for Makefile >> to change it indirectly. >> >> Considering: >> >> arch/foo/lib: >> fancy.c >> >> We want to be able to build it with -DPANTS=32 in the kernel, but the >> bootloader requires -DPANTS_SIZE=30. >> >> Currently we would do, either: >> >> arch/foo/lib/Makefile >> LDFLAGS_fancy.o := -DPANTS=32 >> obj-y += fancy.o >> >> and, either: >> >> arch/foo/boot/Makefile: >> LDFLAGS_fancy.o := -DPANTS=30 >> obj-y += fancy.o >> $(obj)/fancy.c: $(srctree)/arch/foo/lib/fancy.c >>       $(call cmd,shipped) >> >> or >> >> arch/foo/boot/Makefile: >> LDFLAGS_fancy.o := -DPANTS=30 >> obj-y += fancy.o >> $(obj)/fancy.o: $(srctree)/arch/foo/lib/fancy.c >>       $(call cmd,cc_c_o) >> >> The former implies an extra copy of the source file, the latter expose Kbuild >> internal function. >> >> With the attached patch, we would do: >> >> arch/foo/boot/Makefile: >> LDFLAGS_fancy.o := -DPANTS=30 >> obj-y += fancy.o >> vpath-y += $(srctree)/arch/foo/lib >> >> and let GNU make do the job. >> >> Comments welcome, > > It doesn't work.  Whatever I do to arch/arm/boot/compressed/Makefile > (which admittedly looks a bit hairy and could benefit from a shave) in > order to remove the $(call cmd,shipped) used with lib1funcs.S, I always > end up with: > > make[2]: *** No rule to make target `arch/arm/boot/compressed/lib1funcs.S', needed by `arch/arm/boot/compressed/lib1funcs.o'.  Stop. > What was the exact change you made which triggered this ? Thanks, - Arnaud > Obviously, restoring the explicit dependency with a $(call cmd,as_o_S) > does make it work, but this is rather against the point of your patch. > > Do you have an example of how arch/arm/boot/compressed/Makefile should > be changed to benefit from your patch? > > > Nicolas > From mboxrd@z Thu Jan 1 00:00:00 1970 From: lacombar@gmail.com (Arnaud Lacombe) Date: Wed, 7 Sep 2011 15:34:35 -0400 Subject: [RFC] Kbuild: allow code re-use across different directories In-Reply-To: References: <1313800642-32418-1-git-send-email-lacombar@gmail.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org Hi, On Wed, Sep 7, 2011 at 3:07 PM, Nicolas Pitre wrote: > On Fri, 19 Aug 2011, Arnaud Lacombe wrote: > >> Hi folks, >> >> The attached patch modify Kbuild to allow to directly re-use code in multiple >> directory without having to go through a copy. Technically, it changes Kbuild to >> use by default the VPATH feature of GNU make and provides accessors for Makefile >> to change it indirectly. >> >> Considering: >> >> arch/foo/lib: >> fancy.c >> >> We want to be able to build it with -DPANTS=32 in the kernel, but the >> bootloader requires -DPANTS_SIZE=30. >> >> Currently we would do, either: >> >> arch/foo/lib/Makefile >> LDFLAGS_fancy.o := -DPANTS=32 >> obj-y += fancy.o >> >> and, either: >> >> arch/foo/boot/Makefile: >> LDFLAGS_fancy.o := -DPANTS=30 >> obj-y += fancy.o >> $(obj)/fancy.c: $(srctree)/arch/foo/lib/fancy.c >> ? ? ? $(call cmd,shipped) >> >> or >> >> arch/foo/boot/Makefile: >> LDFLAGS_fancy.o := -DPANTS=30 >> obj-y += fancy.o >> $(obj)/fancy.o: $(srctree)/arch/foo/lib/fancy.c >> ? ? ? $(call cmd,cc_c_o) >> >> The former implies an extra copy of the source file, the latter expose Kbuild >> internal function. >> >> With the attached patch, we would do: >> >> arch/foo/boot/Makefile: >> LDFLAGS_fancy.o := -DPANTS=30 >> obj-y += fancy.o >> vpath-y += $(srctree)/arch/foo/lib >> >> and let GNU make do the job. >> >> Comments welcome, > > It doesn't work. ?Whatever I do to arch/arm/boot/compressed/Makefile > (which admittedly looks a bit hairy and could benefit from a shave) in > order to remove the $(call cmd,shipped) used with lib1funcs.S, I always > end up with: > > make[2]: *** No rule to make target `arch/arm/boot/compressed/lib1funcs.S', needed by `arch/arm/boot/compressed/lib1funcs.o'. ?Stop. > What was the exact change you made which triggered this ? Thanks, - Arnaud > Obviously, restoring the explicit dependency with a $(call cmd,as_o_S) > does make it work, but this is rather against the point of your patch. > > Do you have an example of how arch/arm/boot/compressed/Makefile should > be changed to benefit from your patch? > > > Nicolas >