hello_world

Hello World kernel driver

This is a simple example of a kernel driver.

You can compile using:

make ARCH=arm CROSS_COMPILE=<compiler_path>/arm-linux-gnueabihf- -C <linux_path> M=$PWD modules

or using the custom Makefile, you can also compile for your host machine using:

make host

Note you could need to install kernel-devel package for your host machine, i.e:

sudo dnf install kernel-devel.x86_64

You can see some information of compiled driver using:

modinfo main.ko

<compiler_path>/arm-linux-gnueabihf-objdump -h main.ko

Adding in-tree module to kernel menu configuration:

• Create a folder inside linux repository, in drivers/char/<your_name>, for exaple drivers/char/foo.
• Copy main.c inside this folder.
• Copy Kconfig inside this folder.
• Create a Makefile with the following line:

  obj-$(CONFIG_CUSTOM_HELLOWORLD) += main.o

• Add the local Kconfig entry to upper level Kconfig:

  source "drivers/char/foo/Kconfig"
  

• Modify the upper Makefile (in drivers/char/) adding:

  obj-y +=.my_c_dev/

Then you can access to this kernel module executing:

make ARCH=arm menuconfig

The new module will be in Device Drivers ---> Character devices ---> maherme custom modules.