linux 嵌入式驱动程序实例

#include <linux/module.h>

#include <linux/init.h>

#include <linux/fs.h>

#include <linux/kernel.h>

#include <linux/malloc.h>

#include <asm/uaccess.h>

#include <linux/errno.h>

unsigned int fs_major = 0;

static char *data;

statoc struct file_operations chr_fopt = {

read: test_read,

write: test_write,

open: test_open,

release: test_release,

};

static ssize_t test_read(struct file* file,char *buf,size_t count,loff_t *f_pos);

static ssize_t test_write(struct file* file,const char *buffer,size_t count,loff_t *f_pos);

static int test_open(struct inode* inode,struct file* file);

static int test_release(struct inode* inode,struct file* file);

int init_module(vod);

void cleanup_module(void);

static ssize_t test_read(struct file* file,char *buf,size_t count,loff_t *f_pos)

{

int len;

if( count < 0 )

return -EINVAL;

len = strlen(data);

if( len < count )

count = len;

copy_to_user(buf,data,count+1);

return count;

}

static ssize_t test_write(struct file* file,const char *buffer,size_t count,loff_t *f_pos)

{

if( count < 0 )

return -EINVAL;

kfree(data);

data = NULL;

data = (char *)kmalloc(sizeof(char) * (count + 1 ),GFP_KERNEL);

if(!data)

return -ENOMEM;

copy_from_user(data,buffer,count+1);

return count;

}

static int test_open(struct inode* inode,struct file* file)

{

MOD_INC_USE_COUNT;

printf("This is open/n");

return 0;

}

static int test_release(struct inode* inode,struct file* file)

{

MOD_DEC_USE_COUNT;

printf("This is released/n");

return 0;

}

int init_module(vod)

{

int res;

res = register_chrdev(0,"fs",&chr_fops);

if( res < 0 )

{

printfk("can't get major name!/n");

return res;

}

if( fs_major == 0 )

fs_major = res;

return 0;

}

void cleanup_module(void)

{

unregister_chrdev(fs_major,"fs");

}

//arm-linux-gcc -DMODULE -D__KERNEL__ -c kernel.C

//加载模块

//insmod ./kernel.o

//查看设备号

//vi /proc/device

//映射为设备文件

//mknod /dev/fs c 254 0

// dev/fs就是相应的设备文件,c代表字符文件,254代表主设备号,0为次设备号