Character device driver 
================================

.. panels::
        :container: container pb-4
        :column: col-lg-12 p-2
        :card: shadow

        Topics in this section,

                * :ref:`Learnings in this section <FreebsdDeviceDriver_char_fdd_1>`

                * :ref:`Version Info <FreebsdDeviceDriver_char_fdd_2>`

                * :ref:`Setup development environment <FreebsdDeviceDriver_char_fdd_2_1>`

                * :ref:`Architecture <FreebsdDeviceDriver_char_fdd_3>`

                * :ref:`HW : <FreebsdDeviceDriver_char_fdd_4>`

                * :ref:`SW : <FreebsdDeviceDriver_char_fdd_5>`
			
	                * :ref:`Applications & Libraries <FreebsdDeviceDriver_char_fdd_6>`

	                * :ref:`Kernel & Driver modules <FreebsdDeviceDriver_char_fdd_7>`

		                * :ref:`List of driver modules <FreebsdDeviceDriver_char_fdd_8>`

	                * :ref:`Custom build of driver modules <FreebsdDeviceDriver_char_fdd_9>`

		                * :ref:`Complete program : char.c  <FreebsdDeviceDriver_char_fdd_10>`

		                * :ref:`Makefile <FreebsdDeviceDriver_char_fdd_11>`

		                * :ref:`Compile Program <FreebsdDeviceDriver_char_fdd_12>`

	                * :ref:`Load custom built driver modules <FreebsdDeviceDriver_char_fdd_13>`

		                * :ref:`kldload : check if the module is loaded successfully <FreebsdDeviceDriver_char_fdd_14>`

		                * :ref:`dmesg : check what happened on module load <FreebsdDeviceDriver_char_fdd_15>`

		                * :ref:`Write operation <FreebsdDeviceDriver_char_fdd_16>`

		                * :ref:`Read operation <FreebsdDeviceDriver_char_fdd_17>`

		                * :ref:`kldunload : check if the module is unloaded successfully <FreebsdDeviceDriver_char_fdd_18>`

		                * :ref:`check what happened on module unload <FreebsdDeviceDriver_char_fdd_19>`

	                * :ref:`Let us do the character device driver development <FreebsdDeviceDriver_char_fdd_20>`

				* :ref:`Control path debugging <FreebsdDeviceDriver_char_fdd_21>`
                                
                                                        * :ref:`Add prints in nl80211_small_ops <FreebsdDeviceDriver_char_fdd_22>`

                                * :ref:`Data path debugging <FreebsdDeviceDriver_char_fdd_23>`

                                                        * :ref:`Add prints in nl80211_small_ops <FreebsdDeviceDriver_char_fdd_24>`

                * :ref:`FAQs <FreebsdDeviceDriver_char_fdd_25>`

                * :ref:`Reference links <FreebsdDeviceDriver_char_fdd_26>`





.. _FreebsdDeviceDriver_char_fdd_1:
  
.. tab-set::

   .. tab-item:: Learnings in this section

        * In this section, you are going to learn


        .. panels::
                :container: container pb-4
                :column: col-lg-12 p-2
                :card: shadow

                * How to write a Character Device Driver module ?


.. _FreebsdDeviceDriver_char_fdd_2:

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

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


.. _FreebsdDeviceDriver_char_fdd_2_1:

.. tab-set::

   .. tab-item:: Setup development environment

        * Create directory using mkdir command

        .. code-block:: c

                test:~$ pwd
                /home/test/     

                test:~$ mkdir char_device_drivers

                test:~$ cd char_device_drivers

                test:~$ pwd
                home/test/char_device_drivers



.. _FreebsdDeviceDriver_char_fdd_3:

.. tab-set::
 
    .. tab-item:: Architecture

        * Architecture




.. _FreebsdDeviceDriver_char_fdd_4:

.. tab-set::
 
    .. tab-item:: HW

	.. code-block:: c

		test:~$

	
.. _FreebsdDeviceDriver_char_fdd_5:

.. tab-set::
 
    .. tab-item:: SW

	.. _FreebsdDeviceDriver_char_fdd_6:

	.. tab-set::
	 
	    .. tab-item:: Applications & Libraries

		.. code-block:: c

			test:~$ 
 


	.. _FreebsdDeviceDriver_char_fdd_7:

        .. tab-set::
         
            .. tab-item:: Kernel & Driver modules

		.. _FreebsdDeviceDriver_char_fdd_8:

                .. tab-set::
                 
                    .. tab-item:: List of driver modules

                        .. tab-set::
                         
                            .. tab-item:: 1. if_iwlwifi.ko

                                .. csv-table::
                                        :file: ./if_iwlwifi_ko.csv
                                        :widths: 50, 50



	.. _FreebsdDeviceDriver_char_fdd_9:

        .. tab-set::
         
            .. tab-item:: Custom build of driver modules

		.. _FreebsdDeviceDriver_char_fdd_10:

		.. tab-set::

		   .. tab-item:: char.c

			.. literalinclude:: char_device_drivers/char.c
				:language: c
				:linenos:

		.. _FreebsdDeviceDriver_char_fdd_11:

		.. tab-set::

		    .. tab-item:: Makefile

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

		.. _FreebsdDeviceDriver_char_fdd_12:

		.. tab-set::

		    .. tab-item:: Compile Program
			
			.. code-block:: c
				:linenos:
				:emphasize-lines: 1, 5, 9
				
				test:~$ pwd
				home/test/char_device_drivers


				test:~$ ls
				char.c  Makefile  README


				test:~$ make




	.. _FreebsdDeviceDriver_char_fdd_13:

        .. tab-set::
         
            .. tab-item:: Load custom built driver modules

		.. _FreebsdDeviceDriver_char_fdd_14:

		.. tab-set::

		    .. tab-item:: kldload : check if the module is loaded successfully
			
			.. code-block:: c
				:linenos:
				:emphasize-lines: 1
				
				test:~$ kldload -v ./echo.ko

		.. _FreebsdDeviceDriver_char_fdd_15:

		.. tab-set::

		    .. tab-item:: dmesg : check what happened on module load
			
			.. code-block:: c
				:linenos:
				:emphasize-lines: 1
				
				test:~$ dmesg
				Echo device loaded.

		.. _FreebsdDeviceDriver_char_fdd_16:

		.. tab-set::

		    .. tab-item:: Write operation

			* Writing data to the driver (/dev/echo)
			
			.. code-block:: c
				:linenos:
				:emphasize-lines: 1
				
				test:~$ echo -n "Test Data" > /dev/echo
				Opened device "echo" successfully.

				Closing device "echo".


		.. _FreebsdDeviceDriver_char_fdd_17:

		.. tab-set::

		    .. tab-item:: Read operation

			* Reading data from the driver (/dev/echo)
			
			.. code-block:: c
				:linenos:
				:emphasize-lines: 1
				
				test:~$ cat /dev/echo
				Opened device "echo" successfully.
				Test Data
				Closing device "echo".

		.. _FreebsdDeviceDriver_char_fdd_18:

		.. tab-set::

		    .. tab-item:: kldunload : check if the module is unloaded successfully 

			.. code-block:: c
				:linenos:
				:emphasize-lines: 1
				
				test:~$ kldunload echo


		.. _FreebsdDeviceDriver_char_fdd_19:

		.. tab-set::

		    .. tab-item:: check what happened on module unload
			
			.. code-block:: c
				:linenos:
				:emphasize-lines: 1
				
				test:~$ dmesg
				Echo device unloaded.




	.. _FreebsdDeviceDriver_char_fdd_20:

	.. tab-set::

	   .. tab-item:: Let us do character device driver development !

		.. _FreebsdDeviceDriver_char_fdd_21:
	
		.. tab-set::

		   .. tab-item:: Control path debugging
	
			.. _FreebsdDeviceDriver_char_fdd_22:

			.. tab-set::

			   .. tab-item:: Add prints in nl80211_small_ops

				* Open nl80211.c file with vim, add prints in all .doit functions in nl80211_small_ops

				.. code-block:: c

					test:~$ 



		.. _FreebsdDeviceDriver_char_fdd_23:
                        
		.. tab-set::

		   .. tab-item:: Data path debugging

			.. _FreebsdDeviceDriver_char_fdd_24:

			.. tab-set::

			   .. tab-item:: Add prints in nl80211_small_ops

				* Open nl80211.c file with vim, add prints in all .doit functions in nl80211_small_ops

				.. code-block:: c

					test:~$


.. _FreebsdDeviceDriver_char_fdd_25:

.. tab-set::
 
    .. tab-item:: FAQs

                .. code-block:: c

                        test:~$



.. _FreebsdDeviceDriver_char_fdd_26:

.. tab-set::
 
    .. tab-item:: Reference links

                .. code-block:: c

                        test:~$