On Sun, Mar 15, 2009 at 4:09 PM, K <> wrote:
> Hi All,
> For the kernel module if you have just a single .c file for your module
> then your makefile would just contain
>
> "obj-$(CONFIG_YOUR-DIRECTORY-FOR-THE-MODULE) += name_of_your_driver.o"
>
> but lets say if I want to split my module into several .c files then in that
>case how would be my makefile? Finally my objective is to get a single .ko
> file for my driver using all these c files. I am not really good at makefiles
> for the kernel modules so please help.
Have a look at the Documentation/kbuild/makefiles.txt file in the
linux source tree. Section 3.3 is the particular section you want to
read and understand:
+++++++++++++++++++++++++
--- 3.3 Loadable module goals - obj-m
$(obj-m) specify object files which are built as loadable
kernel modules.
A module may be built from one source file or several source
files. In the case of one source file, the kbuild makefile
simply adds the file to $(obj-m).
Example:
#drivers/isdn/i4l/Makefile
obj-$(CONFIG_ISDN_PPP_BSDCOMP) += isdn_bsdcomp.o
Note: In this example $(CONFIG_ISDN_PPP_BSDCOMP) evaluates to 'm'
If a kernel module is built from several source files, you specify
that you want to build a module in the same way as above.
Kbuild needs to know which the parts that you want to build your
module from, so you have to tell it by setting an
$(<module_name>-objs) variable.
Example:
#drivers/isdn/i4l/Makefile
obj-$(CONFIG_ISDN) += isdn.o
isdn-objs := isdn_net_lib.o isdn_v110.o isdn_common.o
In this example, the module name will be isdn.o. Kbuild will
compile the objects listed in $(isdn-objs) and then run
"$(LD) -r" on the list of these files to generate isdn.o.
Kbuild recognises objects used for composite objects by the suffix
-objs, and the suffix -y. This allows the Makefiles to use
the value of a CONFIG_ symbol to determine if an object is part
of a composite object.
Example:
#fs/ext2/Makefile
obj-$(CONFIG_EXT2_FS) += ext2.o
ext2-y := balloc.o bitmap.o
ext2-$(CONFIG_EXT2_FS_XATTR) += xattr.o
In this example, xattr.o is only part of the composite object
ext2.o if $(CONFIG_EXT2_FS_XATTR) evaluates to 'y'.
Note: Of course, when you are building objects into the kernel,
the syntax above will also work. So, if you have CONFIG_EXT2_FS=y,
kbuild will build an ext2.o file for you out of the individual
parts and then link this into built-in.o, as you would expect.
++++++++++++++++++++
Hope that helps.
Ted Roth
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