EmbLogic » char driver https://www.emblogic.com/blog Embedded System and ARM Training Tue, 03 Mar 2020 13:00:06 +0000 en-US hourly 1 http://wordpress.org/?v=3.9.1 What is Character Driver? https://www.emblogic.com/blog/02/what-is-character-driver/ https://www.emblogic.com/blog/02/what-is-character-driver/#comments Sun, 21 Feb 2016 12:10:16 +0000 http://www.emblogic.com/blog/?p=13296 Continue reading →]]> A character device driver is one that transfers data directly to and from a user process.

This is the most common type of device driver and there are plenty of simple examples in the source tree.

Character device drivers may transfer data between a user-level process and the device using any scheme other than the system buffer cache.

Character drivers control devices such as :-

 

——————————————

* network cards

* terminal devices

* printers

* specialized devices such as robots

* medical devices

* retail sales devices.

]]> https://www.emblogic.com/blog/02/what-is-character-driver/feed/ 0 Add the 20 devices and initialise the user defined structure dev in b/w cdev_init and cdev_add https://www.emblogic.com/blog/04/add-the-20-devices-and-initialise-the-user-defined-structure-dev-in-bw-cdev_init-and-cdev_add/ https://www.emblogic.com/blog/04/add-the-20-devices-and-initialise-the-user-defined-structure-dev-in-bw-cdev_init-and-cdev_add/#comments Mon, 27 Apr 2015 10:29:06 +0000 http://www.emblogic.com/blog/?p=12641 Continue reading →]]> 
RCS file: header.h,v
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revision 1.6
date: 2015/04/28 15:54:10;  author: root; 
state: Exp;  lines: +16 -0
define the macro of user defined parameter such
as QUANTUM_SIZE, DATA_SIZE, QSET_SIZE, DEVICE_SIZE.set the default
values.
----------------------------
revision 1.5
date: 2015/04/26 15:51:54;  author: root; 
state: Exp;  lines: +1 -0
removed the struct of cdev.
----------------------------
revision 1.4
date: 2015/04/26 14:41:40;  author: root; 
state: Exp;  lines: +1 -1
introduced the stucture for mapping
stuct Qset, struct dev where our devices node
information is stored.
in struct dev struct cdev is declared
internally.
also declared the extern struct dev *sdev
pointer for mapping
,
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revision 1.3
date: 2015/04/26 13:28:55;  author: root; 
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revision 1.2
date: 2015/04/26 13:18:47;  author: root; 
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*** empty log message ***
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revision 1.1
date: 2015/04/26 13:12:11;  author: root; 
state: Exp;
Initial revision
=============================================================================


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revision 1.7


date: 2015/04/28 15:56:37;  author: root; 
state: Exp;  lines: +2 -6


declared the extern variable of Macros.


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revision 1.6


date: 2015/04/28 12:55:36;  author: root; 
state: Exp;  lines: +1 -0


declared the extern ndev in this.


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revision 1.5


date: 2015/04/26 17:35:00;  author: root; 
state: Exp;  lines: +1 -0


introduced extern file operations variable.


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revision 1.4


date: 2015/04/26 15:52:20;  author: root; 
state: Exp;  lines: +2 -2


include the linux/cdev.h in header.h


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revision 1.3


date: 2015/04/26 14:45:32;  author: root; 
state: Exp;  lines: +19 -0


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revision 1.2


date: 2015/04/26 13:18:47;  author: root; 
state: Exp;  lines: +1 -0


*** empty log message ***


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revision 1.1


date: 2015/04/26 13:12:11;  author: root; 
state: Exp;


Initial revision


=============================================================================




RCS file: new_initialization.c,v


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revision 1.13


date: 2015/04/28 16:20:11;  author: root; 
state: Exp;  lines: +3 -1


same as previous version, just checking.


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revision 1.12


date: 2015/04/28 15:33:55;  author: root; 
state: Exp;  lines: +37 -8


declared the init_dev_parameter() in which
initialise the MACRO quantum_size,qset_size,data_size,device_size.


after that, call first in initial_func() so that
it will be initalized again.


Now, access these parameters through struct dev
variable which should be initialised b/w cdev_init() and cdev_add().


----------------------------


revision 1.11


date: 2015/04/28 13:04:27;  author: root; 
state: Exp;  lines: +2 -1


add the macro MINOR(ndev) to retrive the minor
no.


----------------------------


revision 1.10


date: 2015/04/28 13:00:29;  author: root; 
state: Exp;  lines: +1 -1


change the arugment of MKDEV(). 2nd argument
will be loop index because we gave the minor no.


----------------------------


revision 1.9


date: 2015/04/28 12:51:10;  author: root; 
state: Exp;  lines: +26 -18


register the devices 20 in loop.


declared MKDEV in loop to conmbine the major and
minor value into single one.


change the cdev and add the 20 devices.


----------------------------


revision 1.8


date: 2015/04/26 17:23:35;  author: root; 
state: Exp;  lines: +16 -2


initialize cdev_init and pass the 1st arguement
which is address of cdev which is pointed by object of struct dev.


2nd arguement is address of file_operations.


after cdev_init also initialized owner field and
file_operations *ops field which is actually defined in cdev.h.


after initialization of cdev_init, we need to
make the connection by using cdev_add().


In cdev_add(),mentioned the address pointed by
dev to cdev, 2nd arguement is dev and 3rd one is no. of devices we
added which is nod.


successfully cdev_add() is done, the driver
initilization is complete.


----------------------------


revision 1.7


date: 2015/04/26 16:11:06;  author: root; 
state: Exp;  lines: +4 -3


add the if statement in kmalloc error checking.


----------------------------


revision 1.6


date: 2015/04/26 15:51:07;  author: root; 
state: Exp;  lines: +2 -1


correct the mistake done is kmalloc of FLAG.


----------------------------


revision 1.5


date: 2015/04/26 14:40:00;  author: root; 
state: Exp;  lines: +8 -0


declared kmalloc and provide space into the
kernel.


after that memset flushed the memory.


----------------------------


revision 1.4


date: 2015/04/26 13:30:58;  author: root; 
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revision 1.3


date: 2015/04/26 13:28:53;  author: root; 
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revision 1.2


date: 2015/04/26 13:18:42;  author: root; 
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*** empty log message ***


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revision 1.1


date: 2015/04/26 13:12:11;  author: root; 
state: Exp;


Initial revision


=============================================================================




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revision 1.7


date: 2015/04/28 12:54:55;  author: root; 
state: Exp;  lines: +5 -1


cdev_del is in loop to delete the connection.

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			https://www.emblogic.com/blog/04/add-the-20-devices-and-initialise-the-user-defined-structure-dev-in-bw-cdev_init-and-cdev_add/feed/
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		Initializing a driver using alloc_chrdev_region()
		https://www.emblogic.com/blog/04/initializing-a-driver-using-alloc_chrdev_region/
		https://www.emblogic.com/blog/04/initializing-a-driver-using-alloc_chrdev_region/#comments
		Sat, 25 Apr 2015 10:18:50 +0000
		
				
		
		

		http://www.emblogic.com/blog/?p=12625
		Continue reading →]]>
				RCS file: header.h,v

Working file: header.h

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description:

this is header file


here various header files are included such as module param.h init.h cdev.h slab.h and many others

—————————

revision 1.10

date: 2015/04/24 12:36:40; author: psingh; state: Exp; lines: +1


Here module author,module licence and module description is defined


 


—————————


RCS file: declaration.h,v

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revision 1.6

date: 2015/04/25 00:38:02; author: psingh; state: Exp; lines: +6 -6

This is declaration.h…

here declaration of struct qset is defined

here declaration of struct Dev is also defined

and a structure variable of type Dev is also defined which contains the element *qset and predefined structure cdev as mentioned in cdev.h…


============================================================================


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—————————-

revision 1.1

date: 2015/04/25 00:38:05; author: psingh; state: Exp;

Initial revision

Here file operation structure is taken and declared as extern…

=============================================================================


RCS file: init.c,v

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date: 2015/04/24 10:54:2; author: psingh; state: Exp; lines: +1 -1

Here initalization of module is done using alloc_chrdev_region

after that memory will be allocated by kernel using kmalloc()

—————————

revision 1.6

date: 2015/04/24 10:53:1; author: psingh; state: Exp; lines: +4 -5

cdev structure is initialized and its memory is made NULL by using memset

after that cdev owner and file operation is declared and the addition of device table is done using cdev_add()


————————

=============================================================================


RCS file: clean.c,v

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description:

this is cleanup function


revision 1.2

date: 2015/04/24 10:36:12; author: psingh; state: Exp; lines: +3 -1

first cdev_del will remove the device table from the driver module

after that kfree will free the memory allocated to the structure pointer as defined to the strcut Dev..

then unregisteration of the module will be carried by using unregister_chrdev_region


—————————-

revision 1.1

date: 2015/04/24 10:12:13; author: psingh; state: Exp;

Initial revision

=============================================================================

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		0
		
		
		Project 05: Character Device Driver
		https://www.emblogic.com/blog/11/project-05-character-device-driver/
		https://www.emblogic.com/blog/11/project-05-character-device-driver/#comments
		Fri, 02 Nov 2012 16:52:39 +0000
		
				
		
		
		
		
		
		

		http://emblogic.org/blog/?p=5628
		Continue reading →]]>
				Modules are pieces of code that can be loaded and unloaded into the kernel upon demand. They extend the functionality of the kernel without the need to reboot the system. For example, one type of module is the device driver, which allows the kernel to access hardware connected to the system. Without modules, we would have to build monolithic kernels and add new functionality directly into the kernel image. Besides having larger kernels, this has the disadvantage of requiring us to rebuild and reboot the kernel every time we want new functionality.

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		14
		
		
		ioctl..
		https://www.emblogic.com/blog/11/ioctl/
		https://www.emblogic.com/blog/11/ioctl/#comments
		Fri, 18 Nov 2011 04:56:24 +0000
		
				
		
		

		http://emblogic.org/blog/?p=1268
		Continue reading →]]>
				In the ioctl function at driver level……..,

the switch(cmd) statement have ‘cmd’ as the argument but we can see cmd is of ‘unsigned int’ type…

i want to ask how the switch function perform case matching….

switch(cmd)

{

case IOSQSET:

case IOSQUANTUM:

because after ‘case’ we have written a string..and ‘cmd’ is int type…..how?

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		1