Linux 2.6.32 驱动开发

一、模块

insmod调用module_init

rmmod调用module_exit

module_init(simple_driver_init);

module_exit(simple_driver_exit);

main.c

#include "device_file.h"

#include       /* module_init, module_exit */

#include /* version info, MODULE_LICENSE, MODULE_AUTHOR, printk() */

MODULE_LICENSE("Dual BSD/GPL");

MODULE_AUTHOR("Danil Ishkov, Apriorit");

/*===============================================================================================*/

static int simple_driver_init(void)

{

      int result = 0;

    printk( KERN_NOTICE "Simple-driver: Initialization started" );

      result = register_device();

    return result;

}

/*-----------------------------------------------------------------------------------------------*/

static void simple_driver_exit(void)

{

  printk( KERN_NOTICE "Simple-driver: Exiting" );

    unregister_device();

}

/*===============================================================================================*/

module_init(simple_driver_init);

module_exit(simple_driver_exit);

二、字符设备

register_chrdev

unregister_chrdev

device_file.h

#ifndef DEVICE_FILE_H_

#define DEVICE_FILE_H_

#include /* __must_check */

__must_check int register_device(void); /* 0 if Ok*/

void unregister_device(void);

#endif //DEVICE_FILE_H_

device_file.c

#include "device_file.h"

#include     /* file stuff */

#include     /* printk() */

#include     /* error codes */

#include   /* THIS_MODULE */

#include       /* char device stuff */

#include   /* copy_to_user() */

static const char    g_s_Hello_World_string[] = "Hello world from kernel mode!\n\0";

static const ssize_t g_s_Hello_World_size = sizeof(g_s_Hello_World_string);

/*===============================================================================================*/

static ssize_t device_file_read(

                          struct file *file_ptr

                        , char __user *user_buffer

                        , size_t count

                        , loff_t *possition)

{

  printk( KERN_NOTICE "Simple-driver: Device file is read at offset = %i, read bytes count = %u"

            , (int)*possition

            , (unsigned int)count );

  if( *possition >= g_s_Hello_World_size )

      return 0;

  if( *possition + count > g_s_Hello_World_size )

      count = g_s_Hello_World_size - *possition;

  if( copy_to_user(user_buffer, g_s_Hello_World_string + *possition, count) != 0 )

      return -EFAULT; 

  *possition += count;

  return count;

}

/*===============================================================================================*/

static struct file_operations simple_driver_fops =

{

  .owner  = THIS_MODULE,

  .read    = device_file_read,

};

static int device_file_major_number = 0;

static const char device_name[] = "Simple-driver";

/*===============================================================================================*/

int register_device(void)

{

      int result = 0;

      printk( KERN_NOTICE "Simple-driver: register_device() is called." );

      result = register_chrdev( 0, device_name, &simple_driver_fops );

      if( result < 0 )

      {

        printk( KERN_WARNING "Simple-driver:  can\'t register character device with errorcode = %i", result );

        return result;

      }

      device_file_major_number = result;

      printk( KERN_NOTICE "Simple-driver: registered character device with major number = %i and minor numbers 0...255"

                  , device_file_major_number );

      return 0;

}

/*-----------------------------------------------------------------------------------------------*/

void unregister_device(void)

{

  printk( KERN_NOTICE "Simple-driver: unregister_device() is called" );

  if(device_file_major_number != 0)

  {

      unregister_chrdev(device_file_major_number, device_name);

  }

}

三、实现file_operations

static struct file_operations simple_driver_fops =

{

  .owner  = THIS_MODULE,

  .read    = device_file_read,

};

reference: https://www.apriorit.com/dev-blog/195-simple-driver-for-linux-os