Hello World : Module Parameter
===============================

.. tab-set::

    .. tab-item:: Hello World : Module Parameter

        * In this program, you are going to learn

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

                How to pass module parameters to Linux kernel module ?

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

                * How to use below APIs ?

                        * `module_param <https://elixir.bootlin.com/linux/v6.2/source/include/linux/moduleparam.h#L126>`_

                        * `MODULE_PARM_DESC <https://elixir.bootlin.com/linux/v6.2/source/include/linux/moduleparam.h#L33>`_


.. panels::
        :container: container pb-4
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        Topics in this section,

                * :ref:`Passing arguments <p2_moduleWithParameter_0>`

                * :ref:`Example 1 : passing integer as argument <p2_moduleWithParameter_1>`

                        * :ref:`Makefile for prgm1.c <p2_moduleWithParameter_2>`

                        * :ref:`Compile and Load <p2_moduleWithParameter_3>`

                * :ref:`Example 2 : passing short as argument <p2_moduleWithParameter_4>`

                        * :ref:`Makefile for prgm2.c <p2_moduleWithParameter_5>`

                        * :ref:`Compile and Load <p2_moduleWithParameter_6>`

                * :ref:`Example 3 : passing integer as argument <p2_moduleWithParameter_7>`

                        * :ref:`Makefile for prgm3.c <p2_moduleWithParameter_8>`

                        * :ref:`Compile and Load <p2_moduleWithParameter_9>`

                * :ref:`Example 4 : passing integer as argument <p2_moduleWithParameter_10>`

                        * :ref:`Makefile for prgm4.c <p2_moduleWithParameter_11>`

                        * :ref:`Compile and Load <p2_moduleWithParameter_12>`

                * :ref:`Example 5 : passing integer as argument <p2_moduleWithParameter_13>`

                        * :ref:`Makefile for prgm5.c <p2_moduleWithParameter_14>`

                        * :ref:`Compile and Load <p2_moduleWithParameter_15>`

                * :ref:`Summary <p2_moduleWithParameter_16>`


.. _p2_moduleWithParameter_0:

.. tab-set::

    .. tab-item:: Passing arguments

        * To allow arguments to be passed to your module, declare the variables that will take the values of the command line arguments as global and then use the module_param() macro.


.. _p2_moduleWithParameter_1:

.. tab-set::

    .. tab-item:: Example 1 : passing integer as argument

        * Define the module parameter for integer

        .. code-block:: c

                module_param(myint, int, 0644);

                MODULE_PARM_DESC(myint, "An integer");

        * Pass the module parameter during module load

        .. code-block:: c

                $ sudo insmod ./prgm1.ko myint=56

        * See the full program below,
        
        .. tab-set::

            .. tab-item:: prgm1.c

	        .. literalinclude:: p2_moduleWithParameter/prgm1.c
		        :language: c
		        :linenos:
                        :emphasize-lines: 10, 12, 13

.. _p2_moduleWithParameter_2:

.. tab-set::

    .. tab-item:: Makefile for prgm1.c
        
        .. code-block:: c
                :linenos:
                
                obj-m += prgm1.o

                all:
               	        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

                clean:
                	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

.. _p2_moduleWithParameter_3:

.. tab-set::

    .. tab-item:: Compile and Load
        
        .. code-block:: c
                :linenos:
                :emphasize-lines: 1, 3, 5, 9, 11
                
                $ make all

                $ sudo insmod ./prgm1.ko myint=56

                $ dmesg
                [495039.286549] Hello, world
                [495039.286550] myint is an integer: 56

                $ sudo rmmod prgm1

                $ dmesg 
                [495039.286549] Hello, world
                [495039.286550] myint is an integer: 56
                [495049.549716] Goodbye, world


.. _p2_moduleWithParameter_4:

.. tab-set::

    .. tab-item:: Example 2 : passing short as argument


        * Define the module parameter for short

        .. code-block:: c

                module_param(myshort, short, 0660);

                MODULE_PARM_DESC(myshort, "A short integer");

        * Pass the module parameter during module load

        .. code-block:: c

                $ sudo insmod ./prgm2.ko myshort=10                             

        * See the full program below,


        .. tab-set::

            .. tab-item:: prgm2.c

                .. literalinclude:: p2_moduleWithParameter/prgm2.c
                        :language: c
                        :linenos:
                        :emphasize-lines: 10, 12, 13


.. _p2_moduleWithParameter_5:

.. tab-set::

    .. tab-item:: Makefile for prgm2.c
        
        .. code-block:: c
                :linenos:
                
                obj-m += prgm2.o

                all:
                        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

                clean:
                        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

.. _p2_moduleWithParameter_6:

.. tab-set::

    .. tab-item:: Compile and Load
        
        .. code-block:: c
                :linenos:
                :emphasize-lines: 1, 3, 5, 9, 11
                
                $ make all

                $ sudo insmod ./prgm2.ko myshort=10

                $ dmesg
                [495335.891744] Hello, world
                [495335.891745] myshort is a short integer: 10

                $ sudo rmmod prgm2

                $ dmesg
                [495335.891744] Hello, world
                [495335.891745] myshort is a short integer: 10
                [495343.492308] Goodbye, world 


.. _p2_moduleWithParameter_7:

.. tab-set::

    .. tab-item:: Example 3 : passing long as argument

        * Define the module parameter for long

        .. code-block:: c

                module_param(mylong, long, 0400);

                MODULE_PARM_DESC(mylong, "A long integer");

        * Pass the module parameter during module load

        .. code-block:: c

                $ sudo insmod ./prgm3.ko mylong=500

        * See the full program below,
 
        .. tab-set::

            .. tab-item:: prgm3.c

                .. literalinclude:: p2_moduleWithParameter/prgm3.c
                        :language: c
                        :linenos:
                        :emphasize-lines: 10, 12, 13


.. _p2_moduleWithParameter_8:

.. tab-set::

    .. tab-item:: Makefile for prgm3.c
        
        .. code-block:: c
                :linenos:
                
                obj-m += prgm3.o

                all:
                        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

                clean:
                        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean

.. _p2_moduleWithParameter_9:

.. tab-set::

    .. tab-item:: Compile and Load
        
        .. code-block:: c
                :linenos:
                :emphasize-lines: 1, 3, 5, 9, 11
                
                $ make all

                $ sudo insmod ./prgm3.ko mylong=500

                $ dmesg
                [495455.686602] Hello, world
                [495455.686604] mylong is a long integer: 500

                $ sudo rmmod prgm3

                $ dmesg
                [495455.686602] Hello, world
                [495455.686604] mylong is a long integer: 500
                [495464.038982] Goodbye, world

                
.. _p2_moduleWithParameter_10:

.. tab-set::

    .. tab-item:: Example 4 : passing string as argument

        * Define the module parameter for string

        .. code-block:: c

                module_param(mystring, charp, 0000);

                MODULE_PARM_DESC(mystring, "A character string");

        * Pass the module parameter during module load

        .. code-block:: c

                $ sudo insmod ./prgm4.ko mystring="linux"

        * See the full program below,
 
        .. tab-set::

            .. tab-item:: prgm4.c

                .. literalinclude:: p2_moduleWithParameter/prgm4.c
                        :language: c
                        :linenos:
                        :emphasize-lines: 10, 12, 13

.. _p2_moduleWithParameter_11:

.. tab-set::

    .. tab-item:: Makefile for prgm4.c
        
        .. code-block:: c
                :linenos:
                
                obj-m += prgm4.o

                all:
                        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

                clean:
                        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean


.. _p2_moduleWithParameter_12:

.. tab-set::

    .. tab-item:: Compile and Load
        
        .. code-block:: c
                :linenos:
                :emphasize-lines: 1, 3, 5, 9,  11
                
                $ make all

                $ sudo insmod ./prgm4.ko mystring="linux"

                $ dmesg
                [495668.254605] Hello, world
                [495668.254607] mystring is a string: linux

                $ sudo rmmod prgm4

                $ dmesg 
                [495668.254605] Hello, world
                [495668.254607] mystring is a string: linux
                [495697.631035] Goodbye, world

            
.. _p2_moduleWithParameter_13:

.. tab-set::

    .. tab-item:: Example 5 : passing integer array as argument

        * Define the module parameter for integer array

        .. code-block:: c

                module_param_array(myintArray, int, &arr_argc, 0000);

                MODULE_PARM_DESC(myintArray, "An array of integers");

        * Pass the module parameter during module load

        .. code-block:: c

                $ sudo insmod ./prgm5.ko myintArray=10,20,30

        * See the full program below,
 
        .. tab-set::
             
            .. tab-item:: prgm5.c

                .. literalinclude:: p2_moduleWithParameter/prgm5.c
                        :language: c
                        :linenos:
                        :emphasize-lines: 10, 11, 13, 14


.. _p2_moduleWithParameter_14:

.. tab-set::

    .. tab-item:: Makefile for prgm5.c
        
        .. code-block:: c
                :linenos:
                
                obj-m += prgm5.o

                all:
               	        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

                clean:
                	make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean


.. _p2_moduleWithParameter_15:

.. tab-set::

    .. tab-item:: Compile and Load
        
        .. code-block:: c
                :linenos:
                :emphasize-lines: 1, 3, 5, 13, 15
                
                $ make all

                $ sudo insmod ./prgm5.ko myintArray=10,20,30

                $ dmesg
                [504234.493933] Hello, world
                [504234.493935] myintArray[0] = 10
                [504234.493935] myintArray[1] = 20
                [504234.493936] myintArray[2] = 30
                [504234.493936] got 3 arguments for myintArray.

                
                $ sudo rmmod prgm5

                $ dmesg 
                [504234.493933] Hello, world
                [504234.493935] myintArray[0] = 10
                [504234.493935] myintArray[1] = 20
                [504234.493936] myintArray[2] = 30
                [504234.493936] got 3 arguments for myintArray.
                [504240.118160] Goodbye, world


.. _p2_moduleWithParameter_16:

.. tab-set::

    .. tab-item:: Summary

        =============================== =======================================
        API                             Learning
        =============================== =======================================
        module_param                    macro used to initialize the arguments
        MODULE_PARM_DESC                used to document arguments that the module can take          
        =============================== =======================================



.. card:: See Also

        * Other topic

                * :doc:`p1_basicModule`


        * Next Chapter

                * :doc:`../chapter2_kthreads/chapter2_kthreads`

        * Other Chapters 

                * :doc:`../chapter3_tasklets/chapter3_tasklets`

                * :doc:`../chapter4_workqueue/chapter4_workqueue`

                * :doc:`../chapter5_timer/chapter5_timer`

                * :doc:`../chapter8_linkedList/chapter8_linkedList`

                * :doc:`../chapter9_fileSystem/chapter9_fileSystem`

                * :doc:`../chapter10_netlink/chapter10_netlink`