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下面是成功编译的代码,发出来给大家参考,最近在看ioctl和llseek,有问题再和大家讨论,谢谢大家!
#include <linux/init.h>
#include <linux/module.h>
//#include <linux/kdev_t.h>
#include <linux/fs.h>
#include <linux/cdev.h>
#include <asm/uaccess.h>
MODULE_AUTHOR("Prince Pei");
MODULE_LICENSE("Dual BSD/GPL");
static struct prince_dev {
char *data;
int quantum;
unsigned long size; /* amount of data */
struct cdev cdev;
};
struct prince_dev *prince_device;
static int prince_init_module(void);
static void prince_setup_cdev(struct prince_dev *);
static ssize_t prince_read(struct file *, char __user *, size_t, loff_t *);
//#include <unistd.h>
//ssize_t read(int filedes, void *buf, size_t nbytes);
static ssize_t prince_write(struct file *, const char __user *, size_t, loff_t *);
//#include <unistd.h>
//ssize_t write(int filedes, const void *buf, size_t nbytes);
static int prince_open(struct inode *, struct file *);
static int prince_trim(struct prince_dev *);
static int prince_release(struct inode *, struct file *);
static void prince_cleanup_module(void);
static int prince_major = 0;
static int prince_minor = 0;
static int prince_quantum = 4096;
static void prince_cleanup_module(void)
{
dev_t devno = MKDEV(prince_major, prince_minor);
if (prince_device) {
if (prince_device->data)
kfree(prince_device->data);
cdev_del(&prince_device->cdev);
kfree(prince_device);
}
printk("<1>prince_device was freed SUCCESSLY\n");
//extern void unregister_chrdev_region(dev_t, unsigned);
unregister_chrdev_region(devno, 1);
printk("<1> unregister_character_device_region finish!\n");
}
static ssize_t prince_read(struct file *filp, char __user *buf, size_t count, loff_t *f_pos)
{
printk("<1> prince_read() is invoked!\n");
struct prince_dev *dev = filp->private_data;
ssize_t retval = 0;
if (*f_pos >= dev->size)
goto out;
if (*f_pos + count > dev->size)
count = dev->size - *f_pos;
if (dev->data == NULL)
goto out;
if (copy_to_user(buf, dev->data + *f_pos, count)) {
retval = -EFAULT;
goto out;
}
printk("<1> copy_to_user() SUCCESS!\n");
*f_pos += count;
retval = count;
out:
return retval;
}
static ssize_t prince_write(struct file *filp, const char __user *buf, size_t count, loff_t *f_pos)
{
printk("<1> prince_write() is invoked!\n");
struct prince_dev *dev = filp->private_data;
int quantum = dev->quantum;
ssize_t retval = -ENOMEM;
if (dev->data == NULL) {
dev->data = kmalloc(quantum, GFP_KERNEL);
printk("<1> kmalloc(quantum, GFP_KERNEL) SUCCESS!\n");
if (!dev->data) {
printk("<1> kmalloc(quantum, GFP_KERNLE) FAIL!\n");
goto out;
}
memset(dev->data, 0, quantum);
}
if (count > quantum - *f_pos)
count = quantum - *f_pos;
if (copy_from_user(dev->data + *f_pos, buf, count)) {
retval = -EFAULT;
goto out;
}
printk("<1> prince_write() SUCCESS!\n");
*f_pos += count;
retval = count;
if (dev->size < *f_pos)
dev->size = *f_pos;
out:
return retval;
}
static int prince_trim(struct prince_dev *dev)
{
if (dev->data)
kfree(dev->data);
printk("<1> trim dev->data SUCCESS\n");
dev->data = NULL;
dev->quantum = prince_quantum;
dev->size = 0;
printk("<1> trim reinitial struct prince_dev SUCCESS\n");
return 0;
}
static int prince_open(struct inode *inode, struct file *filp)
{
printk("<1> prince_open() is invoked!\n");
struct prince_dev *dev;
dev = container_of(inode->i_cdev, struct prince_dev, cdev);
printk("<1> container_of SUCCESS!\n");
filp->private_data = dev;
printk("<1> private_data SUCCESS!\n");
if ((filp->f_flags & O_ACCMODE) == O_WRONLY) {
prince_trim(dev);
printk("<1> prince_open invoke prince_trim complete successfully\n");
}
return 0;
}
static int prince_release(struct inode *inode, struct file *filp)
{
printk("<1> prince_release() is invoked!\n");
return 0;
}
struct file_operations prince_fops = {
.owner = THIS_MODULE,
.read = prince_read,
.write = prince_write,
.open = prince_open,
.release = prince_release,
};
static void prince_setup_cdev(struct prince_dev *dev)
{
int err, devno = MKDEV(prince_major, prince_minor);
cdev_init(&dev->cdev, &prince_fops);
dev->cdev.owner = THIS_MODULE;
dev->cdev.ops = &prince_fops;
err = cdev_add(&dev->cdev, devno, 1);
printk("<1> cdev add SUCCESS\n");
if (err)
printk("<1> Error %d adding scull\n", err);
}
static int prince_init_module(void)
{
int result;
dev_t dev = 0;
if (prince_major)
{
dev = MKDEV(prince_major, prince_minor);
result = register_chrdev_region(dev, 1, "prince");
}
else
{
result = alloc_chrdev_region(&dev, prince_minor, 1, "prince");
prince_major = MAJOR(dev);
printk("<1> get major SUCCESS!\n");
}
if (result < 0)
{
printk("<1>prince: cannot get major %d\n", prince_major);
return result;
}
/* allocate the device */
prince_device = kmalloc(sizeof(struct prince_dev), GFP_KERNEL);
if (!prince_device)
{
result = -ENOMEM; //why
goto fail; //how to implement fail:
}
memset(prince_device, 0, sizeof(struct prince_dev));
printk("<1> allocate the device SUCCESS\n");
prince_device->quantum = prince_quantum;
prince_device->size = 0;
prince_setup_cdev(prince_device);
printk("<1> prince_device initialization complete\n");
return 0;
fail:
prince_cleanup_module();
return result;
}
module_init(prince_init_module);
module_exit(prince_cleanup_module); |
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