First Linux driver: Count the numbers of words

To write the Linux driver steps:

1. Build Linux drive skeleton (load and unload Linux drivers)

#include <linux/module.h>

#include <linux/init.h>

#include <linux/init.h>

#include <linux/kernel.h>

#include <linux/fs.h>

#include <linux/miscdevice.h>

#include <asm/uaccess.h>

Initializing Linux drivers

static int word_count_init (void)

{

PRINTK ("word_count_init_success\n");

return 0;

}

Exiting Linux Drivers

static void Word_count_exit (void)

{

PRINTK ("word_count_exit_success\n");

}

Registering initialize Linux-driven functions

Module_init (Word_count_init);

Registering a function that exits the Linux driver

Module_exit (Word_count_exit);

2, specify the information related to the drive

Module_author ("lining"); Module author

Module_description ("Statistics of Word count."); Module description

Module_alias ("Word Count module."); Module aliases

Module_license ("GPL"); Open Source Agreement

3. Registration and cancellation of equipment files

Modify the Word_count.c file

#define DEVICE_NAME "WordCount"//define Device file name

static struct File_operations Dev_fops = {. Owner = this_module}; Describes the callback function pointer corresponding to the event triggered by the device file

static struct Miscdevice Misc =//information describing the device file

{

. minor = Misc_dynamic_minor,//secondary device number, dynamically generated secondary device number (Miscellaneous device master number is 10)

. Name = Device_name,//device file name

. fops = &dev_fops//file_operations struct variable pointer

};

static int word_count_init (void)

{

int ret;

ret = Misc_register (&MISC); Create a device file

return ret;

}

STAITC void Word_exit (void)

{

Misc_deregister (&MISC); Log off (remove) device files

}

4. Specifying a callback function

static unsigned char mem[1000]; Saving data written to a device file

static int word_count = 0; Number of words

#define TRUE-1

#define FALSE 0

Determines whether the specified character is a space (including whitespace, tab, carriage return, line feed)

Static Char Is_spacewhite (char c)

{

if (c = = "| | c = = 9 | | c = = | | c = = 10)

return TRUE;

Else

return FALSE;

}

Count the number of words

static int Get_word_count (const char *BUF)

{

int n = 1;

int i = 0;

char c = ';

Char flag = 0; Handle multiple space-delimited cases, 0: normal, 1: a space has been encountered

if (*buf = = ' + ')

return 0;

The first character is a space, counting from zero

if (Is_spacewhite (*buf) = = TRUE)

N--;

Scan every character in a string

for (; (c = * (buf + i))! = ' + '; i++)

{

Case with only one space separating words

if (flag = = = 1 && is_spacewhite (c) = = FALSE)

Frag = 0;

Cases where words are separated by multiple spaces, ignoring extra spaces

else if (flag = = = 1 && is_spacewhite (c) = = TRUE)

Continue

The number of words plus 1 when the current character is a space

if (Is_spacewhite (c) = = TRUE)

{

n++;

flag = 1;

}

}

If the string ends with one or more spaces, no count (the number of words minus 1)

if (Is_spacewhite (* (buf + i-1) = = TRUE)

n--;

return n;

}

Call this function when reading data from a device file, file: pointing to device files BUF: Saving readable data count: Number of bytes readable PPOs: offset of Read data

Static ssize_t word_count_read (struct file *file, char _user *buf, size_t count, loff_t *ppos)

{

unsigned char temp[4];

Breaks down the number of words (int type) into 4 bytes stored in a buf

Temp[0] = Word_count >> 24;

TEMP[1] = Word_count >> 16;

TEMP[2] = Word_count >> 8;

TEMP[3] = Word_count;

Copy_to_user (buf, (void*) temp, 4);

PRINTK ("Read:word count:%d", (int) count);

return count;

}

Call this function when writing data to a device file

Static ssize_t word_count_write (struct file *file, const char _user *buf, size_t count, loff_t *ppos)

{

ssize_t writen = count;

Copy_from_user (Mem, buf, Count);

Mem[count] = ' + ';

Word_count = Get_word_count (MEM);

PRINTK ("Write:word count:%d", (int) word_count);

return writen;

}

static struct File_operations Dev_fops =

{

. Owner = This_module,

. Read = Word_count_read,

. write = Word_count_write

};

5. Compiler driver

6. Install and uninstall Linux drivers

Install Linux driver: # insmod Word_count.ko

Uninstall Linux driver: # rmmod Word_count

First Linux driver: Count the numbers of words