Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S264184AbUFNUkp (ORCPT ); Mon, 14 Jun 2004 16:40:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S264235AbUFNUko (ORCPT ); Mon, 14 Jun 2004 16:40:44 -0400 Received: from pfepb.post.tele.dk ([195.41.46.236]:21601 "EHLO pfepb.post.tele.dk") by vger.kernel.org with ESMTP id S264184AbUFNUjW (ORCPT ); Mon, 14 Jun 2004 16:39:22 -0400 Date: Mon, 14 Jun 2004 22:48:09 +0200 From: Sam Ravnborg To: Andrew Morton , linux-kernel@vger.kernel.org, Linus Torvalds Subject: Re: [PATCH 5/5] kbuild: external module build doc Message-ID: <20040614204809.GF15243@mars.ravnborg.org> Mail-Followup-To: Andrew Morton , linux-kernel@vger.kernel.org, Linus Torvalds References: <20040614204029.GA15243@mars.ravnborg.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20040614204029.GA15243@mars.ravnborg.org> User-Agent: Mutt/1.4.1i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 6650 Lines: 209 # This is a BitKeeper generated diff -Nru style patch. # # ChangeSet # 2004/06/14 22:21:46+02:00 sam@mars.ravnborg.org # kbuild: Add external module documentation # # Add first version of a document describing how to build external modules. # This is not yet finished, but includes information that is nice to have # documented in the kernel even in a less complete form. # # Signed-off-by: Sam Ravnborg # # Documentation/kbuild/extmodules.txt # 2004/06/14 22:21:32+02:00 sam@mars.ravnborg.org +168 -0 # # Documentation/kbuild/extmodules.txt # 2004/06/14 22:21:32+02:00 sam@mars.ravnborg.org +0 -0 # BitKeeper file /home/sam/bk/kbuild/Documentation/kbuild/extmodules.txt # # Documentation/kbuild/00-INDEX # 2004/06/14 22:21:32+02:00 sam@mars.ravnborg.org +2 -0 # Added extmodules.txt # diff -Nru a/Documentation/kbuild/00-INDEX b/Documentation/kbuild/00-INDEX --- a/Documentation/kbuild/00-INDEX 2004-06-14 22:25:21 +02:00 +++ b/Documentation/kbuild/00-INDEX 2004-06-14 22:25:21 +02:00 @@ -6,3 +6,5 @@ - developer information for linux kernel makefiles modules.txt - how to build modules and to install them +extmodules.txt + - specific information about external modules diff -Nru a/Documentation/kbuild/extmodules.txt b/Documentation/kbuild/extmodules.txt --- /dev/null Wed Dec 31 16:00:00 196900 +++ b/Documentation/kbuild/extmodules.txt 2004-06-14 22:25:21 +02:00 @@ -0,0 +1,168 @@ +Building external modules +========================= +kbuild offers functionality to build external modules, with the +prerequisite that there is a pre-built kernel avialable with full source. +A subset of the targets available when building the kernel is available +when building an external module. + + +Building the module +------------------- +The command looks like his: + + make -C M=`pwd` + +For the above command to succeed the kernel must have been built with +modules enabled. + +To install the modules just being built: + + make -C M=`pwd` modules_install + +More complex examples later, the above should get you going in most cases. + + +Available targets +- - - - - - - - - +$KDIR refer to path to kernel src + +make -C $KDIR M=`pwd` + Will build the module(s) located in current directory. All output + files will be located in the same directory as the module source. + No attemps are made to update the kernel source, and it is + expected that a successfully make has been executed + for the kernel. + +make -C $KDIR M=`pwd` modules + Same as if no target was specified. See description above. + +make -C $KDIR M=$PWD modules_install + Install the external module(s) + +make -C $KDIR M=$PWD clean + Remove all generated files in for the module - not the kernel + +make -C $KDIR M=`pwd` help + help will list the available target when building external + modules. + +Available options: +- - - - - - - - - +$KDIR refer to path to kernel src + +make -C $KDIR + Used to specify where to find the kernel source. + '$KDIR' represent the directory where the kernel source is. + Make will actually change directory to the specified directory + when executed but change back when finished. + +make -C $KDIR M=`pwd` + M= is used to tell kbuild that an external module is being built. + The option given to M= is the directory where the external + module is located. + When an external module is being built only a subset of the + usual targets are avialable. + +make -C $KDIR SUBDIRS=`pwd` + Same as M=. The SUBDIRS= syntax is kept for backwards compatibility. + + +A more advanced example +- - - - - - - - - - - - +This example shows a setup where a distribution has wisely decided +to separate kernel source and output files: + +Kernel src: +/usr/src/linux-/ + +Output from a kernel compile, including .config: +/lib/modules/linux-/build/ + +External module to be compiled: +/home/user/module/src/ + +To compile the module located in the directory above use the +following command: + + cd /home/user/module/src + make -C /usr/src/linux- \ + O=/lib/modules/linux-/build \ + M=`pwd` + +Then to install the module use the following command: + + make -C /usr/src/linux- \ + O=/lib/modules/linux-/build \ + M='pwd` modules_install + +The above are rather long commands, and the following chapter +lists a few tricks to make it all easier. + +Tricks to make it easy +--------------------- +TODO: .... This need to be rewritten...... + +A make line with several parameters becomes tiresome and errorprone +and what follows here is a little trick to make it possible to build +a module only using a single 'make' command. + +Create a makefile named 'Makefile' with the following content: +---> Makefile: + +all: + $(MAKE) -C /home/sam/src/kernel/v2.6 M=`pwd` \ + $(filter-out all,$(MAKECMDGOALS)) + +obj-m := module.o +---> End of Makefile + +When make is invoked it will see the all: rule, and simply call make again with the right parameters. + +If a driver is being developed that is targeted for inclusion in the main kernel, an idea is to seperate out the all: rule to a Makefile nemed makefile (lower capital m) like this: + +---> makefile +all: + $(MAKE) -f Makefile -C /home/sam/src/kernel/v2.6 \ + M=$(PWD) $(MAKECMDGOALS) + +---> End of makefile + +The kbuild makefile will include only a single statement: +---> Makefile: + +obj-m := module.o + +---> End of Makefile +When executing make, it looks for a file named makefile, before a +file named Makefile. Therefor make will pick up the file named with lower capital 'm'. + + +Prepare the kernel for building external modules +------------------------------------------------ +When building external modules the kernel is expected to be prepared. +This includes the precense of certain binaries, the kernel configuration +and the symlink to include/asm. +To do this a convinient target is made: + + make modules_prepare + +For a typical distribution this would look like the follwoing: + + make modules_prepare O=/lib/modules/linux-/build + + +TODO: Fill out the following chapters + +Module versioning +----------------- + +Include files targeted towards kernel include/... +------------------------------------------------- + +Local include files +------------------- + +Binary only .o files +-------------------- +Use _shipped. + - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/