demo_driver.tar.gz_DEMO_copy_from_user_copy_to_user_driver_XP_de

#include <linux/module.h> #include <linux/config.h> #include <linux/init.h> #include <linux/fs.h> #include <asm/uaccess.h> #include <linux/moduleparam.h> #define SUCCESS 0 #define DEVICE_NAME "demodev" /* Dev name as it appears in /proc/devices */ #define BUF_LEN 80 /* Max length of the message from the device */ static int Major = 240; /* Major number assigned to our device driver */ static int Device_Open = 0; /* Is device open? Used to prevent multiple */ static char msg[BUF_LEN]; /* The msg the device will give when asked */ static int device_open(struct inode *inode, struct file *file) { if (Device_Open) { return -EBUSY; } Device_Open++; printk("<1>device_open call\n"); return SUCCESS; } static int device_release(struct inode *inode, struct file *file) { Device_Open --; /* We're now ready for our next caller */ printk("<1>device_release call\n"); return 0; } static ssize_t device_read(struct file *filp, char *buffer, /* The buffer to fill with data */ size_t length, /* The length of the buffer */ loff_t *offset) /* Our offset in the file */ { int bytes_read = 0; if (length < BUF_LEN) { copy_to_user(buffer, msg, length); return length; } else { copy_to_user(buffer, msg, BUF_LEN); return BUF_LEN; } } static ssize_t device_write(struct file *filp, const char *buff, size_t len, loff_t *off) { memset (msg, 0x0, BUF_LEN); if (BUF_LEN > len) { copy_from_user(msg, buff, len); return len; } else { printk ("Support maximum length = %d\n", BUF_LEN); return -EINVAL; } } static struct file_operations fops = { .read = device_read, .write = device_write, .open = device_open, .release = device_release }; static int __init testmod_init(void) { int ret = register_chrdev(Major, DEVICE_NAME, &fops); if (ret < 0) { printk ("Registering the character device failed with %d\n", ret); return ret; } printk("'create driver file: mknod /dev/%s c %d 0'.\n", DEVICE_NAME, Major); memset (msg, 0x0, 80); return 0; } static void __exit testmod_exit(void) { /* Unregister the device */ int ret = unregister_chrdev(Major, DEVICE_NAME);//取消注册 取消了后模块可以unload if (ret < 0) { printk("Error in unregister_chrdev: %d\n", ret); } } module_init(testmod_init); module_exit(testmod_exit);