=== 5. Include files
--- 5.1 How to include files from the kernel include dir
--- 5.2 External modules using an include/ dir
+ --- 5.3 External modules using several directories
=== 6. Module installation
--- 6.1 INSTALL_MOD_PATH
--- 6.2 INSTALL_MOD_DIR
What is covered within this file is mainly information to authors
of modules. The author of an external modules should supply
a makefile that hides most of the complexity so one only has to type
-'make' to buld the module. A complete example will be present in
+'make' to build the module. A complete example will be present in
chapter ยค. Creating a kbuild file for an external module".
--- 2.2 Available targets
- $KDIR refers to path to kernel source top-level directory
+ $KDIR refers to the path to the kernel source top-level directory
make -C $KDIR M=`pwd`
Will build the module(s) located in current directory.
make -C $KDIR M=$PWD modules_install
Install the external module(s).
Installation default is in /lib/modules/<kernel-version>/extra,
- but may be prefixed with INSTALL_MOD_PATH - see separate chater.
+ but may be prefixed with INSTALL_MOD_PATH - see separate chapter.
make -C $KDIR M=$PWD clean
Remove all generated files for the module - the kernel
- source directory is not moddified.
+ source directory is not modified.
make -C $KDIR M=`pwd` help
help will list the available target when building external
--- 2.3 Available options:
- $KDIR refer to path to kernel src
+ $KDIR refers to the path to the kernel source top-level directory
make -C $KDIR
Used to specify where to find the kernel source.
KERNELDIR := /lib/modules/`uname -r`/build
all::
- $(MAKE) -C $KERNELDIR M=`pwd` $@
+ $(MAKE) -C $(KERNELDIR) M=`pwd` $@
# Module specific targets
genbin:
- echo "X" > 8123_bini.o_shipped
+ echo "X" > 8123_bin.o_shipped
endif
EXTRA_CFLAGS := -Iinclude
8123-y := 8123_if.o 8123_pci.o 8123_bin.o
- Note that in the assingment there is no space between -I and the path.
- This is a kbuild limitation and no space must be present.
-
+ Note that in the assignment there is no space between -I and the path.
+ This is a kbuild limitation: there must be no space present.
+
+--- 5.3 External modules using several directories
+
+ If an external module does not follow the usual kernel style but
+ decide to spread files over several directories then kbuild can
+ support this too.
+
+ Consider the following example:
+
+ |
+ +- src/complex_main.c
+ | +- hal/hardwareif.c
+ | +- hal/include/hardwareif.h
+ +- include/complex.h
+
+ To build a single module named complex.ko we then need the following
+ kbuild file:
+
+ Kbuild:
+ obj-m := complex.o
+ complex-y := src/complex_main.o
+ complex-y += src/hal/hardwareif.o
+
+ EXTRA_CFLAGS := -I$(src)/include
+ EXTRA_CFLAGS += -I$(src)src/hal/include
+
+
+ kbuild knows how to handle .o files located in another directory -
+ although this is NOT reccommended practice. The syntax is to specify
+ the directory relative to the directory where the Kbuild file is
+ located.
+
+ To find the .h files we have to explicitly tell kbuild where to look
+ for the .h files. When kbuild executes current directory is always
+ the root of the kernel tree (argument to -C) and therefore we have to
+ tell kbuild how to find the .h files using absolute paths.
+ $(src) will specify the absolute path to the directory where the
+ Kbuild file are located when being build as an external module.
+ Therefore -I$(src)/ is used to point out the directory of the Kbuild
+ file and any additional path are just appended.
=== 6. Module installation
-Modules which are included in the kernel is installed in the directory:
+Modules which are included in the kernel are installed in the directory:
/lib/modules/$(KERNELRELEASE)/kernel
=> Install dir: /frodo/lib/modules/$(KERNELRELEASE)/kernel
INSTALL_MOD_PATH may be set as an ordinary shell variable or as in the
- example above be specified on the commandline when calling make.
+ example above be specified on the command line when calling make.
INSTALL_MOD_PATH has effect both when installing modules included in
the kernel as well as when installing external modules.
=== 7. Module versioning
-Module versioning are enabled by the CONFIG_MODVERSIONS tag.
+Module versioning is enabled by the CONFIG_MODVERSIONS tag.
Module versioning is used as a simple ABI consistency check. The Module
versioning creates a CRC value of the full prototype for an exported symbol and