file_operations中的函数
int (*open) (struct inode *, struct file *)
– 打开函数
int (*release) (struct inode *, struct file *)
– 释放close函数
long (*unlocked_ioctl) (struct file *, unsigned int, unsigned long)
– io控制函数
ssize_t (*read) (struct file *, char __user *, size_t, loff_t *)
– 读函数
ssize_t (*write) (struct file *, const char __user *, size_t, loff_t *)
– 写函数
loff_t (*llseek) (struct file *, loff_t, int)
– 定位函数
驱动测试源码：
/*包含初始化宏定义的头文件,代码中的module_init和module_exit在此文件中*/
#include <linux/init.h>
/*包含初始化加载模块的头文件,代码中的MODULE_LICENSE在此头文件中*/
#include <linux/module.h>
/*定义module_param module_param_array的头文件*/
#include <linux/moduleparam.h>
/*定义module_param module_param_array中perm的头文件*/
#include <linux/stat.h>
/*三个字符设备函数*/
#include <linux/fs.h>
/*MKDEV转换设备号数据类型的宏定义*/
#include <linux/kdev_t.h>
/*定义字符设备的结构体*/
#include <linux/cdev.h>
/*分配内存空间函数头文件*/
#include <linux/slab.h>
/*包含函数device_create 结构体class等头文件*/
#include <linux/device.h>
#define DEVICE_NAME "chardevnode"
#define DEVICE_MINOR_NUM 2
#define DEV_MAJOR 0
#define DEV_MINOR 0
#define REGDEV_SIZE 3000
MODULE_LICENSE("Dual BSD/GPL");
/*声明是开源的，没有内核版本限制*/
MODULE_AUTHOR("SKYFALL");
/*声明作者*/
int numdev_major = DEV_MAJOR;
int numdev_minor = DEV_MINOR;
/*输入主设备号*/
module_param(numdev_major,int,S_IRUSR);
/*输入次设备号*/
module_param(numdev_minor,int,S_IRUSR);
static struct class *myclass;
struct reg_dev
{
char *data;
unsigned long size;
struct cdev cdev;
};
struct reg_dev *my_devices;
/*打开操作*/
static int chardevnode_open(struct inode *inode, struct file *file){
printk("%s,%d\n",__func__,__LINE__);
printk(KERN_EMERG "chardevnode_open is success!\n");
return 0;
}
/*关闭操作*/
static int chardevnode_release(struct inode *inode, struct file *file){
printk("%s,%d\n",__func__,__LINE__);
printk(KERN_EMERG "chardevnode_release is success!\n");
return 0;
}
/*IO操作*/
static long chardevnode_ioctl(struct file *file, unsigned int cmd, unsigned long arg){
printk("%s,%d\n",__func__,__LINE__);
printk(KERN_EMERG "chardevnode_ioctl is success! cmd is %d,arg is %d \n",cmd,arg);
return 0;
}
ssize_t chardevnode_read(struct file *file, char __user *buf, size_t count, loff_t *f_ops){
return 0;
}
ssize_t chardevnode_write(struct file *file, const char __user *buf, size_t count, loff_t *f_ops){
return 0;
}
loff_t chardevnode_llseek(struct file *file, loff_t offset, int ence){
return 0;
}
struct file_operations my_fops = {
.owner = THIS_MODULE,
.open = chardevnode_open,
.release = chardevnode_release,
.unlocked_ioctl = chardevnode_ioctl,
.read = chardevnode_read,
.write = chardevnode_write,
.llseek = chardevnode_llseek,
};
/*设备注册到系统*/
static void reg_init_cdev(struct reg_dev *dev,int index){
int err;
int devno = MKDEV(numdev_major,numdev_minor+index);
/*数据初始化*/
cdev_init(&dev->cdev,&my_fops);
dev->cdev.owner = THIS_MODULE;
dev->cdev.ops = &my_fops;
/*注册到系统*/
err = cdev_add(&dev->cdev,devno,1);
if(err){
printk(KERN_EMERG "cdev_add %d is fail! %d\n",index,err);
}
else{
printk(KERN_EMERG "cdev_add %d is success!\n",numdev_minor+index);
}
}
static int scdev_init(void)
{
int ret = 0,i;
dev_t num_dev;
printk("%s,%d\n",__func__,__LINE__);
printk(KERN_EMERG "numdev_major is %d!\n",numdev_major);
printk(KERN_EMERG "numdev_minor is %d!\n",numdev_minor);
if(numdev_major){
num_dev = MKDEV(numdev_major,numdev_minor);
ret = register_chrdev_region(num_dev,DEVICE_MINOR_NUM,DEVICE_NAME);
}
else{
/*动态注册设备号*/
ret = alloc_chrdev_region(&num_dev,numdev_minor,DEVICE_MINOR_NUM,DEVICE_NAME);
/*获得主设备号*/
numdev_major = MAJOR(num_dev);
printk(KERN_EMERG "adev_region req %d !\n",numdev_major);
}
if(ret<0){
printk(KERN_EMERG "register_chrdev_region req %d is failed!\n",numdev_major);
}
myclass = class_create(THIS_MODULE,DEVICE_NAME);
my_devices = kmalloc(DEVICE_MINOR_NUM * sizeof(struct reg_dev),GFP_KERNEL);
if(!my_devices){
ret = -ENOMEM;
goto fail;
}
memset(my_devices,0,DEVICE_MINOR_NUM * sizeof(struct reg_dev));
printk("%s,%d\n",__func__,__LINE__);
/*设备初始化*/
for(i=0;i<DEVICE_MINOR_NUM;i++){
my_devices[i].data = kmalloc(REGDEV_SIZE,GFP_KERNEL);
memset(my_devices[i].data,0,REGDEV_SIZE);
/*设备注册到系统*/
reg_init_cdev(&my_devices[i],i);
/*创建设备节点*/
device_create(myclass,NULL,MKDEV(numdev_major,numdev_minor+i),NULL,DEVICE_NAME"%d",i);
}
printk(KERN_EMERG "scdev_init!\n");
/*打印信息，KERN_EMERG表示紧急信息*/
return 0;
fail:
/*注销设备号*/
unregister_chrdev_region(MKDEV(numdev_major,numdev_minor),DEVICE_MINOR_NUM);
printk(KERN_EMERG "kmalloc is fail!\n");
return ret;
}
static void scdev_exit(void)
{
int i;
printk("%s,%d\n",__func__,__LINE__);
printk(KERN_EMERG "scdev_exit!\n");
/*除去字符设备*/
for(i=0;i<DEVICE_MINOR_NUM;i++){
cdev_del(&(my_devices[i].cdev));
/*摧毁设备节点函数d*/
device_destroy(myclass,MKDEV(numdev_major,numdev_minor+i));
}
/*释放设备class*/
class_destroy(myclass);
/*释放内存*/
kfree(my_devices);
unregister_chrdev_region(MKDEV(numdev_major,numdev_minor),DEVICE_MINOR_NUM);
}
module_init(scdev_init);
/*初始化函数*/
module_exit(scdev_exit);
/*卸载函数*/应用层测试源码：
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <sys/ioctl.h>
int main(int argc, char * argv[]){
int fd;
char *hello_node0 = "/dev/chardevnode0";
char *hello_node1 = "/dev/chardevnode1";
/*O_RDWR读写方式,O_NDELAY非阻塞方式*/
if((fd = open(hello_node0,O_RDWR|O_NDELAY))<0){
printf("%s,%d\n",__func__,__LINE__);
printf("APP open %s failed!\n",hello_node0);
}
else{
printf("APP open %s success!\n",hello_node0);
}
close(fd);
if((fd = open(hello_node1,O_RDWR|O_NDELAY))<0){
printf("APP open %s failed!\n",hello_node1);
}
else{
printf("%s,%d\n",__func__,__LINE__);
printf("APP open %s success!\n",hello_node1);
}
close(fd);
return 0;
}
相应的Makefile参考相关的博文，将编译好的驱动和应用程序加载至开发板上测试。