Hello World
===============================

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        Topics in this section,

                * :ref:`Version Info <FreebsdDeviceDriver_basic_fdd_hello_world_0>`

                * :ref:`Learnings in this section <FreebsdDeviceDriver_basic_fdd_hello_world_1>`

                * :ref:`Setup development environment <FreebsdDeviceDriver_basic_fdd_hello_world_2>`

                * :ref:`Complete program : hello.c <FreebsdDeviceDriver_basic_fdd_hello_world_3>`

                * :ref:`Makefile <FreebsdDeviceDriver_basic_fdd_hello_world_4>`

                * :ref:`Compile Program <FreebsdDeviceDriver_basic_fdd_hello_world_5>`

                * :ref:`Load the module <FreebsdDeviceDriver_basic_fdd_hello_world_6>`

                * :ref:`Check if the module is loaded successfully <FreebsdDeviceDriver_basic_fdd_hello_world_7>`

                * :ref:`Check what happened on module load <FreebsdDeviceDriver_basic_fdd_hello_world_8>`

                * :ref:`Unload the module <FreebsdDeviceDriver_basic_fdd_hello_world_9>`

                * :ref:`Check if the module is unloaded successfully <FreebsdDeviceDriver_basic_fdd_hello_world_10>`

                * :ref:`Check what happened on module unload <FreebsdDeviceDriver_basic_fdd_hello_world_11>`


.. _FreebsdDeviceDriver_basic_fdd_hello_world_0:

.. tab-set::
 
    .. tab-item:: Version Info

        =============================== =======================================
        #                               Version
        =============================== =======================================
        Freebsd                         14.1.0
        =============================== =======================================


.. _FreebsdDeviceDriver_basic_fdd_hello_world_1:

.. tab-set::

    .. tab-item:: Learnings in this section

        * In this program, you are going to learn

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                * How to write a sample kernel module ?


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                * How to write Makefile to compile driver module ?

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                * How to check if module is loaded successfully ?

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                * How to check if module is unloaded successfully ?

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                * How to check prints from kernel modules ?


.. _FreebsdDeviceDriver_basic_fdd_hello_world_2:

.. tab-set::

   .. tab-item:: Setup development environment

	* Create directory using mkdir command

	.. code-block:: c

		test:~$ pwd
		/home/test/	

		test:~$ mkdir basic_device_drivers

		test:~$ cd basic_device_drivers

		test:~$ mkdir hello_world

		test:~$ cd hello_world

		test:~$ pwd
		/home/test/basic_device_drivers/hello_world


.. _FreebsdDeviceDriver_basic_fdd_hello_world_3:

.. tab-set::

   .. tab-item:: hello.c

        .. literalinclude:: hello_world/hello.c
                :language: c
                :linenos:


.. _FreebsdDeviceDriver_basic_fdd_hello_world_4:

.. tab-set::

    .. tab-item:: Makefile

        .. literalinclude:: hello_world/Makefile
                :language: c
                :linenos:


.. _FreebsdDeviceDriver_basic_fdd_hello_world_5:

.. tab-set::

    .. tab-item:: Compile Program
        
        .. code-block:: c
                :linenos:
                :emphasize-lines: 1, 5, 9, 11
                
                $ pwd
                basic_device_drivers/hello_world


                $ ls
                hello.c  Makefile 


                $ make

		$ ls
		.depend.hello.o  export_syms  hello.c  hello.o  hello_world.ko  i386  machine  Makefile  opt_global.h  x86


.. _FreebsdDeviceDriver_basic_fdd_hello_world_6:

.. tab-set::

    .. tab-item:: Load the module 

        * Load the module using kldload
        
        .. code-block:: c
                :linenos:
                :emphasize-lines: 1

                $ kldload ./hello_world.ko
		Loaded ./kthread_module.ko, id=8


.. _FreebsdDeviceDriver_basic_fdd_hello_world_7:

.. tab-set::

    .. tab-item:: Check if the module is loaded successfully

	* Run kldstat command to check the loaded modules
        
        .. code-block:: c
                :linenos:
                :emphasize-lines: 1, 10
                
                $ kldstat
                Id Refs Address                Size Name
                 1   29 0xffffffff80200000  1f6c698 kernel
                 2    1 0xffffffff8216d000     7850 cryptodev.ko
                 3    1 0xffffffff82176000   772c70 zfs.ko
                 4    1 0xffffffff83218000     3220 intpm.ko
                 5    1 0xffffffff8321c000     2178 smbus.ko
                 6    1 0xffffffff8321f000     3360 uhid.ko
                 7    1 0xffffffff83223000     3360 wmt.ko
                 8    1 0xffffffff83227000     209c hello_world.ko



.. _FreebsdDeviceDriver_basic_fdd_hello_world_8:

.. tab-set::

    .. tab-item:: Check what happened on module load
        
	* Run dmesg command to check the kernel logs

        .. code-block:: c
                :linenos:
                :emphasize-lines: 1
                
                $ dmesg
		Hello KLD loaded.


.. _FreebsdDeviceDriver_basic_fdd_hello_world_9:

.. tab-set::

    .. tab-item:: Unload the module 

        * Unload the module using kldunload
        
        .. code-block:: c
                :linenos:
                :emphasize-lines: 1

                $ kldunload -v ./hello_world.ko
                Unloading hello_world.ko, id=8



.. _FreebsdDeviceDriver_basic_fdd_hello_world_10:
 
.. tab-set::

    .. tab-item:: Check if the module is unloaded successfully 

	* Run kldstat command to check the loaded modules
        
        .. code-block:: c
                :linenos:
                :emphasize-lines: 1
                
                $ kldstat
                Id Refs Address                Size Name
                 1   27 0xffffffff80200000  1f6c698 kernel
                 2    1 0xffffffff8216d000     7850 cryptodev.ko
                 3    1 0xffffffff82176000   772c70 zfs.ko
                 4    1 0xffffffff83218000     3220 intpm.ko
                 5    1 0xffffffff8321c000     2178 smbus.ko
                 6    1 0xffffffff8321f000     3360 uhid.ko
                 7    1 0xffffffff83223000     3360 wmt.ko



.. _FreebsdDeviceDriver_basic_fdd_hello_world_11:

.. tab-set::

    .. tab-item:: Check what happened on module unload

	* Run dmesg command to check the kernel logs
        
        .. code-block:: c
                :linenos:
                :emphasize-lines: 1
                
                $ dmesg
		Hello KLD unloaded