Re: compiling external modules

[Axel Weiss]

Hi, Sam,

excuse me (and forget my previous mail), I've found the reason for the missing 
exported symbols in the C-source.

I will continue simplifying the Makefile...

Regards,
Axel

On Friday 16 April 2004 14:06, Axel Weiss wrote:
> Hi, Sam,
>
> I have patched to 2.6.6-rc1 (patch-2.6.6-rc1 over kernel 2.6.5 - am I right
> or am I missing some patches in between?), and now symbol exports between
> modules fails. An example with two module-objects - one exports some
> symbols used by the other - shows compile output:
>
> scripts/Makefile.build:36: kbuild: /home/axel/freeSP-1.0.4/drivers/linux/
> adc64/busmaster/Makefile - Usage of export-objs is obsolete in 2.6. Please
> fix!
>
> 8<
>
> *** Warning: "adc64_count" [/home/axel/freeSP-1.0.4/drivers/linux/adc64/
> driver/adc64.ko] undefined!
> *** Warning: "release_adc64_busmaster"
> [/home/axel/freeSP-1.0.4/drivers/linux/ adc64/driver/adc64.ko] undefined!
> *** Warning: "get_adc64_busmaster" [/home/axel/freeSP-1.0.4/drivers/linux/
> adc64/driver/adc64.ko] undefined!
>
> 8<
>
> The first (exporting) module loads cleanly (lsmod shows the loaded module),
> but insmod'ing the second fails with:
>
> insmod: error inserting './adc64.ko': -1 Unknown symbol in module
>
> What's the trick in 2.6.6?
>
> Regards,
> Axel
>
> On Thursday 15 April 2004 23:59, Sam Ravnborg wrote:
> > On Thu, Apr 15, 2004 at 11:05:49PM +0200, Axel Weiss wrote:
> > > Hi,
> > >
> > > after some study of kernel Makefiles, I'm able now to compile externel
> > > modules for both, 2.4 and 2.6 kernels correctly. I'd like to share my
> > > Makefiles here, maybe somebody finds them useful.
> >
> > Thanks.
> >
> > > 2.6-compilation of drivers consisting of more than one module leaded to
> > > very ugly warnings from scripts/Makefile.modpost, when make was invoked
> > > after 'make clean'. The reason were lying-around objects in
> > > .tmp_versions directory which were not deleted by 'make clean'.
> > > Solution: clean must explicitly delete the version-object in
> > > .tmp_versions.
> >
> > With 2.6.5-rc1 the warning are gone.
> >
> > > 2.4-compilation requires inclusion of Rules.make and an additional rule
> > > for module-object linkage. In 2.6 Rules.make does not exist, and the
> > > linking rule would conflict with an already defined one. Solution:
> > > distinct current kernel version.
> >
> > You should be able to use:
> > -include Rules.make
> >
> > See 'info make' - look after the include directive.
> >
> > > When I gave the rule:
> > > clean:
> > > 	$(MAKE) -C $(KDIR) SUBDIRS=$(PWD) clean
> > > the whole kernel tree was cleaned. This is not my intention, when I'm
> > > working on external modules and want to make clean e.g. for cvs
> > > commits. So I defined my own clean rule, kicking away everything but
> > > source files.
> >
> > With 2.6.5-rc1 this will only cause files in the $(PWD) dir to be
> > deleted, not the kernel tree.
> >
> > > So far the difficulties. Next I propose an assumption about filenames,
> > > when a module consists of several objects which will be linked
> > > together. Let <module-name> be a basic name for the module, so
> > > <module-name>.(k)o (with k for 2.6, without for 2.4) will be the final
> > > target. I assume that all elementary object-filenames begin with
> > > <module-name>, for
> > > clarification. E.g. the module adc64.ko is composed of adc64_module.o,
> > > adc64_device.o, adc64_io.o and so on. Generally, the name of an object
> > > is <module-name>_<object-name>.o, and the object-names can be collected
> > > in a symbol <module-name>-obj-names. Some objects may export symbols to
> > > other modules, they can be collected in a <module-name>-exp-names list.
> >
> > I really do not see the benefit compared to the current more free
> > naming scheme - which works.
> >
> > > Finally, all the modules' Makefiles were very similar, so I split them
> > > into two files: one Makefile for every module and a common
> > > Makefile.module which is included by each Makefile. Each
> > > module-specific Makefile contains the definition of
> > > - <module-name>
> > > - <module-name>-obj-names
> > > - <module-name>-exp-names
> > > - EXTRA_CFLAGS
> > > which makes up all information Makfile.module needs.
> >
> > The general feedback is that it looks like you have
> > made it less simple than it ought to be.
> >
> > You should also consider that you end up with files
> > that does not look like ordinary kbuild makefiles.
> >
> > When I get some spare time I will try to come up with a simpler example.
> >
> > 	Sam
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