Linux Clean Env To Build Driver

Generate Environment to Build Kernel Object

There is no necessary to build driver with full kernel source tree.

For example, in ubuntu, only bellow files are required:

~$ ls /usr/src/linux-headers-3.13.0-32
arch           drivers   init     kernel    net       sound   virt
block          firmware  ipc      lib       samples   tools
crypto         fs        Kbuild   Makefile  scripts   ubuntu
Documentation  include   Kconfig  mm        security  usr

Most of it are header files.

But only kernel headers is not enough. For example, bellow way to generate headers can only be used for userspace.

#cd to the top directory of the kernel source
cd linux-3.9
make mrproper
make ARCH=arm integrator_defconfig
make ARCH=arm headers_check
make ARCH=arm INSTALL_HDR_PATH=path/to/install/headers headers_install

refer to stackoverflow

Here is the document for how to build it.

[1] How to Rebuild An Official Debian Kernel Package

[2] Driver Porting: compiling external modules

If need to do it by yourself, bellow scripts may help.

# remove code in directory
rmcode()
{
    find $1 ! -path '*.git' -name '*.s' -delete
    find $1 ! -path '*.git' -name '*.S' -delete
    find $1 ! -path '*.git' -name '*.c' -delete
    find $1 ! -path '*.git' -name '*.cc' -delete
    find $1 ! -path '*.git' -name '*.cpp' -delete
    find $1 ! -path '*.git' -name Android.mk -delete
}

# release the kernel source
release_kernel()
{
    cd $src
    make clean ARCH=arm CROSS_COMPILE=arm-eabi- # maybe can't clean
    cd $dst
    cp -rf $src $dst
    rmcode $dst
    cp -rf $src/scripts $dst/scripts  # scripts must be original
}

TODO: can we clean it more? Or just do after upon stackoverflow scripts to generate headers?

Build Kernel Object

This' a good example http://www.cyberciti.biz/tips/build-linux-kernel-module-against-installed-kernel-source-tree.html

Here is another one.

.
hello
├── hello.c
└── Makefile

hello.c

#include <linux/module.h>
#include <linux/kernel.h>

static int __init hello_init(void)
{
    printk(KERN_INFO "%s: hello\n", __func__);
    return 0;
}

static void __exit hello_exit(void)
{
    printk(KERN_INFO "%s: bye\n", __func__);
}

MODULE_LICENSE("GPL v2");
MODULE_AUTHOR("Yongsen Chen");
MODULE_DESCRIPTION("Kernel Module Test Code");
MODULE_VERSION("1.00");

module_init(hello_init);
module_exit(hello_exit);

Makefile

CROSS_COMPILE ?= arm-eabi-
ARCH ?= arm

# if define KERNELRELEASE, then build from kernel
ifneq ($(KERNELRELEASE),)
    obj-m += hello.o
# else, it's called from current directory
# must call -C to change the directory
else
    KDIR ?= ../kernel/linux-3.10/

default:
    $(MAKE) -C $(KDIR) M=$(CURDIR) ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE) modules

clean:
    $(MAKE) -C $(KDIR) M=$(CURDIR) ARCH=$(ARCH) CROSS_COMPILE=$(CROSS_COMPILE) clean
endif

Run make, then get the hello.ko.

You can inject it to target device to test it.

Notes

It's not same as to genereate linux kernel headers, we need more. If just generate headers for userspace, see here:

genereate the headers

generate the scripts like debian, see /usr/src/ here are references:

refer to code search: https://codesearch.debian.net/