Nancyvarkey at 13:27, 21 July 2020

2020-07-21T13:27:06Z

Nancyvarkey at 13:08, 21 July 2020

2020-07-21T13:08:35Z

Nirmala Venkat: Created page with " {| style="border-spacing:0;" | style="border:1pt solid #000000;padding:0.176cm;"| '''Visual cue.''' | style="border:1pt solid #000000;padding:0.176cm;"| '''Narration'''. |-..."

2020-07-21T10:10:24Z

Created page with " {| style="border-spacing:0;" | style="border:1pt solid #000000;padding:0.176cm;"| '''Visual cue.''' | style="border:1pt solid #000000;padding:0.176cm;"| '''Narration'''. |-..."

New page

{| style="border-spacing:0;"
| style="border:1pt solid #000000;padding:0.176cm;"| '''Visual cue.'''
| style="border:1pt solid #000000;padding:0.176cm;"| '''Narration'''.

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Slide 1:

Welcome slide:
| style="border:1pt solid #000000;padding:0.176cm;"| Welcome to the spoken tutorial on '''Passing Parameters to a Module.'''

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Slide 2:

Learning objectives:
| style="border:1pt solid #000000;padding:0.176cm;"| In this tutorial, we will learn how to

* Pass parameters to a '''module'''.
|-
| style="border:1pt solid #000000;padding:0.176cm;"| Slide 3:

System Requirements:

| style="border:1pt solid #000000;padding:0.176cm;"| To record this tutorial, I am using,

* '''VirtualBox version 5.2'''
* '''Ubuntu Linux 18.04 LTS''' operating system.
* '''Linux kernel 5.0.0-31 generic'''
* '''gedit text editor.'''
|-
| style="border:1pt solid #000000;padding:0.176cm;"| Slide 4:

Prerequisites
| style="border:1pt solid #000000;padding:0.176cm;"| To follow this tutorial, you should be familiar with:

* '''C programming language '''and
* Basics of''' Linux kernel'''

If not, then go through the '''C/C++''' and '''Linux''' spoken tutorials on this website.

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Point to the '''folder''' and''' file''' in '''desktop'''

Point to the '''files.'''
| style="border:1pt solid #000000;padding:0.176cm;"| Go to the '''DeviceDriver '''folder in the desktop which we have created earlier.

Here, I have created a '''directory named Parameter.'''

In this '''directory''', I have saved a '''module file '''for demonstration purposes.

I have named it as '''mod_param dot c.'''

|-
| style="border:1pt solid #000000;padding:0.176cm;"| slide:

Code files
| style="border:0.5pt solid #000000;padding:0.176cm;"| * The '''files''' used in this tutorial are available in the '''Code Files '''link on this tutorial page.
* Please download and extract them
* Make a copy and then use them while practising
|-
| style="border:1pt solid #000000;padding:0.176cm;"| Open the '''terminal'''

Type >> '''cd Desktop\DeviceDriver\Parameter'''
| style="border:1pt solid #000000;padding:0.176cm;"| Open the '''terminal''' by pressing '''ALT+Ctrl+T '''keys simultaneously.

Press''' Enter''' after every command.

Go to the directory''' Parameter '''as shown here.

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Highlight '''mod_param.c file.'''
| style="border:1pt solid #000000;padding:0.176cm;"| First we will see an example on how to pass '''parameters''' to a '''module.'''

Let us open the file''' mod underscore param dot c.'''

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Type >> '''gedit mod_param.c'''
| style="border:1pt solid #000000;padding:0.176cm;"| Type '''gedit space mod_param dot c '''

Let us look at the''' code'''.

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Highlight '''header files.'''

Highlight'''<nowiki> #include<linux/moduleparam.h></nowiki>'''

Highlight '''<nowiki>int value, array_value[4], value, i.</nowiki>'''
| style="border:1pt solid #000000;padding:0.176cm;"| We have to include these''' header files''' as it is needed by all '''modules.'''

'''moduleparam.h file '''contains the macros required to pass parameters to a module.

Here variables are declared in a '''module''' as '''global variables.'''

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Highlight '''module_param().'''

Highlight '''name '''

Highlight''' type'''

'''// type- bool, int, long, short, uint, ulong, ushort, char*'''
| style="border:1pt solid #000000;padding:0.176cm;"| '''module_param() macro''' is used to pass parameters to a module.

The first''' '''parameter specifies the '''name''' of a parameter.

The '''second''' parameter specifies the supported data types of variable.

For example, '''bool, int, long, short, uint, ulong, ushort '''are supported.

A '''char''' '''pointer''' value is also supported.
|-
| style="border:1pt solid #000000;padding:0.176cm;"| Highlight '''perm'''

Highlight''' S_I'''

| style="border:1pt solid #000000;padding:0.176cm;"| The''' third '''parameter specifies the '''permissions''' of this '''module file''' in''' sysfs. '''

The '''permissions''' can be specified in '''S_I''' format.

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Slide 5:

'''File''' permissions in '''S_I''' format

| style="border:1pt solid #000000;padding:0.176cm;"| Let us see the file permissions in the '''module param() '''macro using''' S_I defines.'''

We can use these formats in our '''code''' as per the requirement.

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Switch back to the '''code'''
| style="border:1pt solid #000000;padding:0.176cm;"| Switch back to the '''code.'''
|-
| style="border:1pt solid #000000;padding:0.176cm;"| Highlight '''value'''

Highlight '''int'''

Highlight''' S_IRUSR | S_IWUSR'''
| style="border:1pt solid #000000;padding:0.176cm;"| Here, I have passed the n'''value''' parameter of''' integer''' data type to a '''module.'''

The''' '''next '''parameter''' indicates that the user has the read and write''' permissions.'''

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Highlight''' module_param_array(array_value, int, NULL, S_IRUSR|S_IWUSR)'''

Highlight '''int'''

Highlight '''NULL'''

Highlight '''S_IRUSR | S_IWUSR'''

| style="border:1pt solid #000000;padding:0.176cm;"| '''module_param_array macro''' is used to send the '''array''' as a '''parameter'''.

The''' array underscore value''' specifies the name of an '''array'''.

Here, the data type of '''array '''elements is '''int.'''

The third parameter is a''' pointer.'''

In this parameter, the '''kernel''' stores the number of''' array elements.'''

Here, we are passing a '''NULL''' pointer.

The''' '''next parameter indicates that '''user''' has the read and write permissions.

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Highlight '''module_param_named'''

Highlight''' name'''

Highlight''' value'''

Highlight '''int'''

Highlight '''S_IRUSR | S_IWUSR'''
| style="border:1pt solid #000000;padding:0.176cm;"| '''module_param_named''' '''macro''' is used to give different names to the same '''variable.'''

Here, '''name''' is the externally viewable parameter.

The''' value '''is the name of the internal global variable.

The data type of this '''variable''' is an '''integer'''.

The''' user''' can read and write to this''' file.'''

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Highlight''' init_function(void)'''

Highlight''' printk messages'''

Highlight '''exit_function(void)'''

Highlight '''printk message'''
| style="border:1pt solid #000000;padding:0.176cm;"| This is an '''initialization function''' of a '''module '''containing the '''printk''' messages.

The '''printk''' messages will print the different parameters of the above macro.

The''' exit function '''is the '''cleanup function''' of the '''module'''.

This function contains a printk message as shown here.

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Open the''' terminal.'''
| style="border:1pt solid #000000;padding:0.176cm;"| Now, save this''' file '''and close the window.

Switch back to the''' terminal.'''

'''Clear the screen.'''
|-
| style="border:1pt solid #000000;padding:0.176cm;"| Type >> '''gedit Makefile'''

Press '''Enter'''

Highlight '''obj-m += mod_param.o '''

Save and close a''' file.'''

Open the''' terminal.'''
| style="border:1pt solid #000000;padding:0.176cm;"| Let us create a '''Makefile '''to compile the '''module. '''

Type '''gedit space Makefile.'''

Write the''' code '''as shown here.

Save this '''file '''and '''close '''it.
|-
| style="border:1pt solid #000000;padding:0.176cm;"| Type >>''' make all'''

Type >>''' sudo su'''

Type >>''' clear.'''
| style="border:1pt solid #000000;padding:0.176cm;"| To build the '''module, '''type '''make space all.'''

Type '''sudo''' '''space''' '''su '''to be a''' superuser '''and

type the system password.

Clear the screen'''.'''
|-
| style="border:1pt solid #000000;padding:0.176cm;"| Type >> '''insmod mod_param.ko value=4 name=9 array_value=11,12,13,14'''

Highlight 4 and 9.

Highlight 11,12,13,14.
| style="border:1pt solid #000000;padding:0.176cm;"| Let us insert '''mod_param'''.'''ko''' into the '''kernel'''.

Type the''' command '''as shown.

Here, we pass a value 4 to the variable''' nvalue '''and''' '''9 to the variable '''name'''.

11,12,13,14 are passed as an '''array''' element to '''array underscore value. '''

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Type >>''' dmesg | grep my_module '''

Highlight the output

Type >> '''clear'''
| style="border:1pt solid #000000;padding:0.176cm;"| Let us see the loaded''' printk''' messages of a module.

Type''' dmesg space pipe space grep space my underscore module '''

These printk messages which display the parameter passes to a module.

Clear the '''screen.'''

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Type '''rmmod mod_param.ko '''

| style="border:1pt solid #000000;padding:0.176cm;"| Let us unload a''' module''' from the''' kernel.'''

Type''' rmmod space mod param dot ko.'''

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Type >>''' dmesg | grep my_module'''

Highlight the output

Type >> '''clear'''
| style="border:1pt solid #000000;padding:0.176cm;"| Let us see the unloaded '''printk''' messages of a '''module.'''

Type '''dmesg space pipe space grep space my underscore module '''

The output shows the printk messages from the exit function.

'''Clear the screen'''

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Type >> '''make clean'''
| style="border:1pt solid #000000;padding:0.176cm;"| Type '''make space clean.'''

It removes all '''files '''created after '''compilation.'''

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Type >> '''exit'''
| style="border:1pt solid #000000;padding:0.176cm;"| To be''' '''the''' regular user, '''type '''exit.'''

|-
| style="border:1pt solid #000000;padding:0.176cm;"|
| style="border:1pt solid #000000;padding:0.176cm;"| With this, we come to the end of this tutorial. Let us summarize.

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Slide 5:

summary:
| style="border:1pt solid #000000;padding:0.176cm;"| In this tutorial, we learnt to,
* Pass parameters to a '''module'''.
|-
| style="border:1pt solid #000000;padding:0.176cm;"| Slide 6:

Assignment:
| style="border:1pt solid #000000;padding:0.176cm;"| As an assignment:

# Compile the '''mod_param.c. '''
# Load the '''module''' with change in parameters value using the '''insmod tool.'''
# See the output using '''dmesg command. '''
# Unload the module using '''rmmod tool.'''

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Slide 7:

About Spoken Tutorial Project:
| style="border:0.5pt solid #000000;padding:0.176cm;"| * The video at the following link summarizes the Spoken Tutorial project.

* Please download and watch it.
|-
| style="border:1pt solid #000000;padding:0.176cm;"| Slide 8:

Spoken Tutorial Workshop:
| style="border:0.5pt solid #000000;padding:0.176cm;"| The '''Spoken Tutorial Project '''Team:

* conducts workshops and
* gives certificates.

For more details, please write to us
|-
| style="border:1pt solid #000000;padding:0.176cm;"| Slide 9:

Forum For Specific Questions:
| style="border:0.5pt solid #000000;padding:0.176cm;"| Please post your timed queries in this forum.

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Slide 10:

Forum For Specific Questions:
| style="border:0.5pt solid #000000;padding:0.176cm;"| * Do you have any general or technical questions on Embedded Linux Device Driver?

* Please visit the FOSSEE forum and post your question..

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Slide 11:

Acknowledgement:
| style="border:0.5pt solid #000000;padding:0.176cm;"| The Spoken Tutorial project is funded by MHRD, Government of India.

|-
| style="border:1pt solid #000000;padding:0.176cm;"| Slide 12:

Thank you slide:
| style="border:0.5pt solid #000000;padding:0.176cm;"| This tutorial has been contributed by FOSSEE and Spoken Tutorial Project, IIT Bombay.

This is Mayuri Panchakshari from IIT Bombay signing off.

Thanks for watching.

|}

@@ Line 14: / Line 14: @@
 Learning objectives:
-| style="border:1pt solid #000000;padding:0.176cm;"| In this tutorial, we will learn how to
+| style="border:1pt solid #000000;padding:0.176cm;"| In this tutorial, we will learn how to pass '''parameters''' to a '''module'''.
-−
-* Pass '''parameters''' to a '''module'''.
 |-
 | style="border:1pt solid #000000;padding:0.176cm;"| Slide 3:
@@ Line 65: / Line 63: @@
 | style="border:1pt solid #000000;padding:0.176cm;"| Open the '''terminal''' by pressing '''ALT+Ctrl+T '''keys simultaneously.
-Press''' Enter''' after every command.
+Press''' Enter''' after every '''command'''.
 Go to the '''directory Parameter '''as shown here.
@@ Line 162: / Line 160: @@
 Here, we are passing a '''NULL pointer'''.
-The next '''parameter''' indicates that '''user''' has the '''read''' and '''write permissions.'''
+The next '''parameter''' indicates that user has the '''read''' and '''write permissions.'''
 |-
@@ Line 182: / Line 180: @@
 The '''data type''' of this '''variable''' is an '''integer'''.
-The''' user''' can '''read''' and '''write''' to this''' file.'''
+The user can '''read''' and '''write''' to this''' file.'''
 |-
@@ Line 222: / Line 220: @@
 Write the code as shown here.
 Save this '''file '''and close it.
@@ Line 232: / Line 231: @@
 | style="border:1pt solid #000000;padding:0.176cm;"| To '''build''' the '''module, '''type '''make space all.'''
-Type '''sudo space su '''to be a''' superuser.'''
+Type '''sudo space su '''to be a''' superuser''' and type the '''system password'''.
-−
-And type the '''system password'''.
 Clear the screen.
@@ Line 313: / Line 310: @@
 | style="border:1pt solid #000000;padding:0.176cm;"| As an assignment:
-# Compile the '''mod_param.c. '''
+# '''Compile''' the '''mod_param.c. '''
 # Load the '''module''' with change in '''parameters value''' using the '''insmod tool.'''
 # See the output using '''dmesg command. '''

Embedded-Linux-Device-Driver/C2/Passing-Parameters-to-a-Module/English - Revision history

Nancyvarkey at 13:27, 21 July 2020

Nancyvarkey at 13:08, 21 July 2020

Nirmala Venkat: Created page with " {| style="border-spacing:0;" | style="border:1pt solid #000000;padding:0.176cm;"| '''Visual cue.''' | style="border:1pt solid #000000;padding:0.176cm;"| '''Narration'''. |-..."