Compile multiple modules with a single makefile

[Henrique Rodrigues]

Hi Valdis,

On Fri, Apr 26, 2013 at 12:48 PM, <Valdis.Kletnieks at vt.edu> wrote:

> On Fri, 26 Apr 2013 11:11:09 -0700, Henrique Rodrigues said:
>
> > I have the one .c source file that I want to create multiple kernel
> modules
> > out of it by setting macros using the makefile.
>
> Generally considered ugly by the mainstream kernel.
>

I agree. I'm actually trying to split the code that was given to me into
three modules with minimal effort (without having to rewrite new code).
The behavior of the code is defined by lots of #if macros in it, and I
wanted to take advantage of that by rewriting only the makefile.

The problem is that if I set the obj-m variable within a make target
(instead of defining it globally), the kernel build system doesn't compile
anything.


>
> > The idea is that if -DMODULE1 is set, I'll build module1.ko and if
> > -DMODULE2 is set, I'll build module 2.
>
> The way this would usually be done is splitting your module into 3
> parts - one common, one for device 1 and one for device 2.
>
> Then something like this (cut-n-paste from
> drivers/net/wireless/hostap/Makefile:
>
> hostap-y := hostap_80211_rx.o hostap_80211_tx.o hostap_ap.o hostap_info.o \
>             hostap_ioctl.o hostap_main.o hostap_proc.o
> obj-$(CONFIG_HOSTAP) += hostap.o
>
> obj-$(CONFIG_HOSTAP_CS) += hostap_cs.o
> obj-$(CONFIG_HOSTAP_PLX) += hostap_plx.o
> obj-$(CONFIG_HOSTAP_PCI) += hostap_pci.o
>
> Which will build 3 different modules (_cs, _plx, _pci) using the common C
> files
> and 1 device-specific C file for each one.
>

I checked the hostap code and it looks like each file (_cs, _plx, _pci)
defines a different module. I believe that is not exactly what I wanted,
but I understand that it works.

Thanks,
-- 
Henrique Rodrigues
http://www.dcc.ufmg.br/~hsr
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