├── Makefile
├── README.md
├── device_file.c
├── device_file.h
└── main.c


/Makefile:
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 1 | TARGET_MODULE:=simple-module
 2 | 
 3 | # If we running by kernel building system
 4 | ifneq ($(KERNELRELEASE),)
 5 | 	$(TARGET_MODULE)-objs := main.o device_file.o
 6 | 	obj-m := $(TARGET_MODULE).o
 7 | 
 8 | # If we are running without kernel build system
 9 | else
10 | 	BUILDSYSTEM_DIR:=/lib/modules/$(shell uname -r)/build
11 | 	PWD:=$(shell pwd)
12 | 
13 | 
14 | all : 
15 | # run kernel build system to make module
16 | 	$(MAKE) -C $(BUILDSYSTEM_DIR) M=$(PWD) modules
17 | 
18 | clean:
19 | # run kernel build system to cleanup in current directory
20 | 	$(MAKE) -C $(BUILDSYSTEM_DIR) M=$(PWD) clean
21 | 
22 | load:
23 | 	insmod ./$(TARGET_MODULE).ko
24 | 
25 | unload:
26 | 	rmmod ./$(TARGET_MODULE).ko
27 | 
28 | endif
29 | 
30 | 


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/README.md:
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1 | # Simple Linux Driver
2 | Simple Linux driver
3 | 


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/device_file.c:
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 1 | #include "device_file.h"
 2 | #include <linux/fs.h> 	    /* file stuff */
 3 | #include <linux/kernel.h>   /* printk() */
 4 | #include <linux/errno.h>    /* error codes */
 5 | #include <linux/module.h>   /* THIS_MODULE */
 6 | #include <linux/cdev.h>     /* char device stuff */
 7 | #include <linux/uaccess.h>  /* copy_to_user() */
 8 | 
 9 | static const char g_s_Hello_World_string[] = "Hello world from kernel mode!\n\0";
10 | static const ssize_t g_s_Hello_World_size = sizeof(g_s_Hello_World_string);
11 | 
12 | /*===============================================================================================*/
13 | static ssize_t device_file_read(
14 |     struct file *file_ptr
15 |     , char __user *user_buffer
16 |     , size_t count
17 |     , loff_t *possition)
18 | {
19 |     printk( KERN_NOTICE "Simple-driver: Device file is read at offset = %i, read bytes count = %u\n"
20 |         , (int)*possition
21 |         , (unsigned int)count );
22 | 
23 |     if( *possition >= g_s_Hello_World_size )
24 |         return 0;
25 | 
26 |     if( *possition + count > g_s_Hello_World_size )
27 |         count = g_s_Hello_World_size - *possition;
28 | 
29 |     if( copy_to_user(user_buffer, g_s_Hello_World_string + *possition, count) != 0 )
30 |         return -EFAULT;
31 | 
32 |     *possition += count;
33 |     return count;
34 | }
35 | 
36 | /*===============================================================================================*/
37 | static struct file_operations simple_driver_fops = 
38 | {
39 |     .owner = THIS_MODULE,
40 |     .read = device_file_read,
41 | };
42 | 
43 | static int device_file_major_number = 0;
44 | static const char device_name[] = "Simple-driver";
45 | 
46 | /*===============================================================================================*/
47 | int register_device(void)
48 | {
49 |     int result = 0;
50 | 
51 |     printk( KERN_NOTICE "Simple-driver: register_device() is called.\n" );
52 | 
53 |     result = register_chrdev( 0, device_name, &simple_driver_fops );
54 |     if( result < 0 )
55 |     {
56 |         printk( KERN_WARNING "Simple-driver:  can\'t register character device with errorcode = %i\n", result );
57 |         return result;
58 |     }
59 | 
60 |     device_file_major_number = result;
61 |     printk( KERN_NOTICE "Simple-driver: registered character device with major number = %i and minor numbers 0...255\n"
62 |         , device_file_major_number );
63 | 
64 |     return 0;
65 | }
66 | 
67 | /*===============================================================================================*/
68 | void unregister_device(void)
69 | {
70 |     printk( KERN_NOTICE "Simple-driver: unregister_device() is called\n" );
71 |     if(device_file_major_number != 0)
72 |     {
73 |         unregister_chrdev(device_file_major_number, device_name);
74 |     }
75 | }
76 | 


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/device_file.h:
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1 | #ifndef DEVICE_FILE_H_
2 | #define DEVICE_FILE_H_
3 | #include <linux/compiler.h> /* __must_check */
4 | 
5 | __must_check int register_device(void); /* 0 if Ok*/
6 | void unregister_device(void);
7 | 
8 | #endif //DEVICE_FILE_H_
9 | 


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/main.c:
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 1 | #include "device_file.h"
 2 | #include <linux/init.h>       /* module_init, module_exit */
 3 | #include <linux/module.h>     /* version info, MODULE_LICENSE, MODULE_AUTHOR, printk() */
 4 | 
 5 | MODULE_DESCRIPTION("Simple Linux driver");
 6 | MODULE_LICENSE("GPL");
 7 | MODULE_AUTHOR("Apriorit, Inc");
 8 | 
 9 | /*===============================================================================================*/
10 | static int simple_driver_init(void)
11 | {
12 |     int result = 0;
13 |     printk( KERN_NOTICE "Simple-driver: Initialization started\n" );
14 | 
15 |     result = register_device();
16 |     return result;
17 | }
18 | 
19 | /*===============================================================================================*/
20 | static void simple_driver_exit(void)
21 | {
22 |     printk( KERN_NOTICE "Simple-driver: Exiting\n" );
23 |     unregister_device();
24 | }
25 | 
26 | /*===============================================================================================*/
27 | module_init(simple_driver_init);
28 | module_exit(simple_driver_exit);
29 | 


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