Linux驱动——实现对设备文件的读写操作和ioctl操作

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我是靠谱客的博主简单滑板，最近开发中收集的这篇文章主要介绍Linux驱动——实现对设备文件的读写操作和ioctl操作，觉得挺不错的，现在分享给大家，希望可以做个参考。

概述

#include <linux/init.h>
#include <linux/module.h>
#include <linux/cdev.h>
#include <linux/fs.h>
#include <linux/device.h>
#include <asm/uaccess.h>
#define DEV_MINOR 0
#define DEV_CNT 1
#define DEV_DATA_SIZE 127
#define DEV_ONE _IO('j', 0)
#define DEV_TWO _IO('j', 1)
char data[DEV_DATA_SIZE + 1] = {0};
ssize_t myread (struct file * fp, char __user * buf, size_t size, loff_t * offset)
{
int ret;
printk("enter myreadn");
if(size > DEV_DATA_SIZE) {
size = DEV_DATA_SIZE;
}
ret = copy_to_user(buf, data, size);
if(ret) {
printk("copy to user error.n");
return -EFAULT;
}
return 0;
}
int myrelease (struct inode * pnode, struct file * fp)
{
printk("enter myreleasen");
return 0;
}
int myopen (struct inode * pnode, struct file * fp)
{
printk("enter myopenn");
return 0;
}
ssize_t mywrite (struct file * fp, const char __user *buf, size_t size, loff_t *offset)
{
int ret;
printk("enter writen");
if(size > 127) {
printk("size is invalid.n");
return -ENOMEM;
}
ret = copy_from_user(data, buf, size);
if(ret) {
printk("copy from user error.n");
return -EFAULT;
}
return 0;
}
long myioctl (struct file * fp, unsigned int cmd, unsigned long data)
{
switch(cmd) {
case DEV_ONE:
printk("DEV ONEn");
break;
case DEV_TWO:
printk("DEV WTOn");
break;
default:
printk("invalid input.n");
break;
}
return 0;
}
dev_t dev;
const struct file_operations myfops ={
.owner = THIS_MODULE,
.open = myopen,
.read = myread,
.write = mywrite,
.release = myrelease,
.unlocked_ioctl = myioctl
};
struct cdev mycdev;
struct class *chrdev_class;
struct device *mydevice;
int chrdev_init(void)
{
int ret;
ret = alloc_chrdev_region(&dev, DEV_MINOR, DEV_CNT, "chrdev");
if(ret < 0) {
printk("alloc_chrdev_region failed!n");
goto alloc_chrdev_fail;
}
cdev_init(&mycdev, &myfops);
ret = cdev_add(&mycdev, dev, DEV_CNT);
if(ret < 0) {
printk("cdev_add failed!n");
goto alloc_chrdev_region_fail;
}
chrdev_class = class_create(THIS_MODULE, "chrdevs");
if(IS_ERR_OR_NULL(chrdev_class)) {
printk("class_create failed.n");
goto class_create_fail;
}
mydevice = device_create(chrdev_class, NULL, dev, NULL, "mydevice" );
if(IS_ERR_OR_NULL(mydevice)) {
printk("device_create failed.n");
goto device_create_fail;
}
printk("chrdev init completed.n");
return 0;
device_create_fail:
class_destroy(chrdev_class);
class_create_fail:
cdev_del(&mycdev);
alloc_chrdev_region_fail:
unregister_chrdev_region(dev, DEV_CNT);
alloc_chrdev_fail:
return -ENODEV;
}
void chrdev_exit(void)
{
device_destroy(chrdev_class, dev);
class_destroy(chrdev_class);
cdev_del(&mycdev);
unregister_chrdev_region(dev, DEV_CNT);
printk("device unregister completed.n");
}
module_init(chrdev_init);
module_exit(chrdev_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("David-Woo");
MODULE_DESCRIPTION("char device driver example");