#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");
MODULE_AUTHOR("lan");
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, "chardev0")){
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, "my_class");
if(IS_ERR(my_class)) {
printk("Err: failed in creating class.\n");
return -1;
}
/* register your own device in sysfs, and this will cause udevd to create corresponding device node */
device_create(my_class, NULL, dev, NULL, "chardev0");
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("nn = %ld\n", nn);
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);
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