First you log in as a super user

$ su

$ password: *******

After you log in as a super user, download these packages given below.

yum install arduino

yum install java-1.7.0-openjdk

After running these two commands , you will find arduino executable file in your file system . Run the executable file.

1. The memory we allocate for creating qsets are architecture dependent, because qsets are the array of pointers which points to quantums i.e. they store the address of quantums.

2. so , for creating 8qsets in 32bit system we need to allocate 32 bytes of memory while in 64 bit system we need to allocate 64bytes of memory

Testing….
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revision 1.2
date: 2014/03/01 09:20:00;  author: root;  state: Exp;  lines: +9 -1
Printing the address inside filep->private_data to check whether it matches with the address returned by container_of() macro.
A local variable of type Sculldev is declared which will store the address that is present inside filep->private_data.
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revision 1.1
date: 2014/02/28 21:33:05;  author: root;  state: Exp;
Initial revision

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, (defined in linux/moduleparam.h) to set the mechanism up. At runtime, insmod will fill the variables with any command line arguments that are given, like ./insmod mymodule.ko myvariable=5

RCS file: header.h,v
Working file: header.h
head: 1.1
branch:
locks: strict
raghav: 1.1
access list:
symbolic names:
keyword substitution: kv
total revisions: 1;    selected revisions: 1
description:
including linux/moduleparam.h
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revision 1.1    locked by: raghav;
date: 2014/02/21 03:49:24;  author: raghav;  state: Exp;
Initial revision
=============================================================================

RCS file: entry.c,v
Working file: entry.c
head: 1.1
branch:
locks: strict
raghav: 1.1
access list:
symbolic names:
keyword substitution: kv
total revisions: 1;    selected revisions: 1
description:
included module_param()
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revision 1.1    locked by: raghav;
date: 2014/02/21 03:52:45;  author: raghav;  state: Exp;
Initial revision
=============================================================================

With function remove() we can delete/remove any file from the file system . remove function takes argument as path of the file . and on success it returns 0.

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revision 1.5    locked by: raghav;
date: 2014/02/16 13:50:15;  author: raghav;  state: Exp;  lines: +1 -0
remove function returns 0 on sucess .
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revision 1.4
date: 2014/02/16 13:48:28;  author: raghav;  state: Exp;  lines: +1 -1
use of remove function to remove the file by writing the path of the file which we want to delete
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revision 1.3
date: 2014/02/16 13:47:46;  author: raghav;  state: Exp;  lines: +1 -1
input the name of file which we want to delete using gets function
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revision 1.2
date: 2014/02/16 13:46:43;  author: raghav;  state: Exp;  lines: +1 -1
*** empty log message ***
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revision 1.1
date: 2014/02/16 13:46:14;  author: raghav;  state: Exp;
Initial revision
=============================================================================

1. Insert your character device driver inside the kernel using insmod and check its entry in the device driver table using cat /proc/devices and note down its major minor number.

2. Now make a node using mknod following with node name character and major minor number example :   mknod nod c 250 0

3. Next step is to run a file (application.c) in the application layer and through the help of node open the file inside the kernel  :    fd=open(“nod”,O_RDWR);

include this statement in the file (application.c) which is in the application layer

4. After executing the application.c file which is in the application layer. check the fd returned by open function. If it is positive, that means file is opened successfully.

5.Last step to unlink the node using unlink node and remove the driver using rmmod

/////////////////////////////////////////////////////////////////////////////

RCS file: clean.c,v
Working file: open.c
head: 1.5
branch:
locks: strict
raghav: 1.5
access list:
symbolic names:
keyword substitution: kv
total revisions: 5;    selected revisions: 5
description:
Creating a node between user and kernerl level using mknod following with node name and c for character device driver and combination of major minor no.
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revision 1.5    locked by: raghav;
date: 2014/02/13 11:20:48;  author: raghav;  state: Exp;  lines: +2 -0
creating a file in application layer and now this file will open the file inside the kernel level using node
we can check it: whether its working or not by printing the fd returned from open func. if its negative then operation unsuccessful.
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revision 1.4
date: 2014/02/13 10:19:28;  author: raghav;  state: Exp;  lines: +1 -1
Error detected: defination of scull_open function whose arguments are struct i node and struct file
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revision 1.3
date: 2014/02/13 10:18:05;  author: raghav;  state: Exp;  lines: +6 -5

Including the open.o in the Make file.
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revision 1.2
date: 2014/02/13 06:09:06;  author: raghav;  state: Exp;  lines: +3 -5
included the struct file_operation Scull_ops.
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revision 1.1
date: 2014/02/13 05:58:43;  author: raghav;  state: Exp;
Initial revision
=============================================================================

RCS file: clean.c,v
Working file: clean.c
head: 1.5
branch:
locks: strict
raghav: 1.5
access list:
symbolic names:
keyword substitution: kv
total revisions: 5;    selected revisions: 5
description:
included the unregister_chrdev_region to unregister the device
to do so we need the major minor number.
which we’ll get from the first argv of alloc_chrdev_region
as i am using seperate files so , i have to use this dev_t dev as a extern in exit function
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revision 1.5    locked by: raghav;
date: 2014/02/13 11:20:48;  author: raghav;  state: Exp;  lines: +2 -0
adding kfree function to free the allocated memory of struct sculldev after removing and un registering the device
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revision 1.4
date: 2014/02/13 10:19:28;  author: raghav;  state: Exp;  lines: +1 -1
Error detected: In the second argument of unregister_chrdev_region func() we have to input only that number of drivers which we have registered.
suppose if we have register our driver for 10 devices then in the unregister fun() we have to unregister 10 devices i.e give 10 in the second argument of unregister function.
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revision 1.3
date: 2014/02/13 10:18:05;  author: raghav;  state: Exp;  lines: +6 -5
Error in un registering the driver from the driver table
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revision 1.2
date: 2014/02/13 06:09:06;  author: raghav;  state: Exp;  lines: +3 -5
included the unregister_chrdev_region to unregister the driver, but here its return type is void
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revision 1.1
date: 2014/02/13 05:58:43;  author: raghav;  state: Exp;
Initial revision
=============================================================================

1. there is no return type of unregister_chrdev_region , so you can check the result only by using vim /proc/devices after rmmod command

2. suppose if you are registering 10 devices using  alloc_chrdev_region then you have to give 10 on the second argument of unregister_chrdev_region function, else it will not remove the driver entry from the driver table.

RCS file: clean.c,v
Working file: clean.c
head: 1.4
branch:
locks: strict
access list:
symbolic names:
keyword substitution: kv
total revisions: 4;    selected revisions: 4
description:
included the unregister_chrdev_region to unregister the device
to do so we need the major minor number.
which we’ll get from the first argv of alloc_chrdev_region
as i am using seperate files so , i have to use this dev_t dev as a extern in exit function
—————————-
revision 1.4
date: 2014/02/13 10:19:28;  author: raghav;  state: Exp;  lines: +1 -1
Error detected: In the second argument of unregister_chrdev_region func() we have to input only that number of drivers which we have registered.
suppose if we have register our driver for 10 devices then in the unregister fun() we have to unregister 10 devices i.e give 10 in the second argument of unregister function.
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revision 1.3
date: 2014/02/13 10:18:05;  author: raghav;  state: Exp;  lines: +6 -5
Error in un registering the driver from the driver table
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revision 1.2
date: 2014/02/13 06:09:06;  author: raghav;  state: Exp;  lines: +3 -5
included the unregister_chrdev_region to unregister the driver, but here its return type is void
—————————-
revision 1.1
date: 2014/02/13 05:58:43;  author: raghav;  state: Exp;
Initial revision
=============================================================================

Example: when ever we copy a file or folder from one location to another in windows OS it usually displays  a graph , a moving file, time remaining, how much memory remaining etc. All such things are called processes. But you must have noticed one thing that actually these are different processes which runs under a same program.

so there is parent process and child process. The process which creates another process is called parent process and latter is called child process. And each process has its own PID i.e. process identity number to distinguish the child from the parent.

To get these process IDs in the program

The functions are

getpid() // to get the current process id

getppid() // to get the creator/ parent process id

There are three methods of creating a process:

1. Create a process with the use  of loader from file system.

2. Create a process from the code segment of the current program using system call

3. Duplication of the program

The easiest one is to use a Duplication of  a program

To create a process using this method is done by using “fork()”

fork function is a special function use to create a child process from a parent process. Using fork(), child process shares the code segment of its parent but both processes have different physical address. After completion of the child process, child process returns its control to parent and the parent process returns its control to the shell.

child PID= parent PID + 1

PPID of child = PID of parent

fork() returns three values and we can use these values to know which process  is executing

fork() returns following values

0 (zero)    :  if the process is executed by child

+ve value :  means child is created and +ve value is child’s PID

-ve value  :  ERROR…! i.e. child process is not created.

NOTE: child process and Parent process both are the part of same program and execute at the same time. It depends on the scheduler that which process executes in which order…….!

Rest i will surely update about how to manage these processes and i will add more stuff related to Process management ….soon…!