linux驱动基本结构分析

/*driver test code */

#include <linux/kernel.h>

#include <linux/module.h>

#include <linux/init.h>

#include <linux/cdev.h>

#include <linux/fs.h>

#include <linux/sched.h>

#include <asm/uaccess.h>

#include <linux/device.h>

MODULE_LICENSE("GPL");

static int char_read(struct file *filp, char __user *buffer, size_t, loff_t*);

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

static int char_write(struct file *filp, const char __user *buffer, size_t, loff_t*);

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

static int chropen;

struct cdev *chardev;

struct class *my_class;

static int len;

static dev_t dev;

static char *to;

static const struct file_operations char_ops={

.read = char_read,

.write = char_write,

.open = char_open,

.release = char_release,

};

static int __init char_init(void)

{

printk(KERN_ALERT"Initing......\n");

chardev = cdev_alloc();

if(chardev == NULL){

return -1;

}

if(alloc_chrdev_region(&dev, 0, 10, "xmimx")) /*动态分配设备号*/

{

printk(KERN_ALERT"Register char dev error\n");

return -1;

}

chropen = 0;

len = 0;

cdev_init(chardev, &char_ops);

if(cdev_add(chardev, dev, 1)){

printk(KERN_ALERT"Add char dev error!\n");

}

my_class = class_create(THIS_MODULE, "xmimx_class"); /*创建一个类*/

if(IS_ERR(my_class)) {

printk("Err: failed in creating class.\n");

return -1;

}

device_create(my_class, NULL, dev, NULL, "xmimx"); /*创建设备节点，并向系统注册该设备*/

return 0;

}

#define DP_MAJOR MAJOR(dev)

#define DP_MINOR MINOR(dev)

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

{

if(chropen == 0)

chropen++;

else{

printk(KERN_ALERT"Another process open the char device\n");

return -1;

}

try_module_get(THIS_MODULE);

return 0;

}

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

{

chropen--;

module_put(THIS_MODULE);

return 0;

}

static int char_read(struct file *filp,char __user *buffer,size_t length,loff_t *offset)

{

unsigned long nn;

nn = copy_to_user(buffer, to, length);

printk("buffer = %s\n", buffer);

return length;

}

static int char_write(struct file *filp, const char __user *buffer, size_t length, loff_t *offset)

{

unsigned long n;

to = (char *)kmalloc((sizeof(char)) * (length+1), GFP_KERNEL);

memset(to, '\0', length+1);

n = copy_from_user(to, buffer, length);

printk("n = %ld\n", n);

printk("to = %s\n", to);

return length;

}

static void __exit module_close(void)

{

len=0;

printk(KERN_ALERT"Unloading..........\n");

unregister_chrdev_region(MKDEV(DP_MAJOR,DP_MINOR),10);

cdev_del(chardev);

device_destroy(my_class, dev);

class_destroy(my_class);

}

module_init(char_init);

module_exit(module_close);

/********************************************************************************/

/*app code*/

#include<sys/types.h>

#include<unistd.h>

#include<fcntl.h>

#include<linux/rtc.h>

#include<linux/ioctl.h>

#include<stdio.h>

#include<stdlib.h>

main()

{

int fd;

int i;

char data[256];

int retval;

fd=open("/dev/xmimx",O_RDWR);

if(fd==-1)

{

perror("error open\n");

exit(-1);

}

printf("open /dev/xmimx ok\n");

retval=write(fd,"David Zeng",10);

if(retval==-1)

{

perror("write error\n");

exit(-1);

}

memset(data, '\0', 256);

retval=read(fd,data,10);

if(retval==-1)

{

perror("read error\n");

exit(-1);

}

data[retval] = '\0';

printf("read ok:%s\n",data);

close(fd);

}

/***************************************************/

/*****makefile*****/

TARGET=demo2

KDIR=/usr/src/linux-headers-2.6.32-25-generic

PWD=$(shell pwd)

obj-m:=$(TARGET).o

default:

make -C $(KDIR) M=$(PWD) modules

clean:

rm -rf *.o *.ko *.mod.c .*.cmd *~ .tmp_versions modules.order Module.symvers $(TARGET)_test

install:

sudo insmod $(TARGET).ko

uninstall:

sudo rmmod $(TARGET)

test:

gcc -o $(TARGET)_test $(TARGET)_test.c

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