eleni@0: #include <asm/uaccess.h>
eleni@0: #include <linux/fs.h>
eleni@0: #include <linux/kernel.h>
eleni@0: #include <linux/module.h>
eleni@0: #include <linux/slab.h>
eleni@0: 
eleni@0: #define DEV_NAME "ktest"
eleni@0: 
eleni@0: static int ktest_init(void);
eleni@0: static void ktest_fini(void);
eleni@0: 
eleni@0: static int ktest_open(struct inode *inode, struct file *file);
eleni@0: static int ktest_release(struct inode *inode, struct file *file);
eleni@0: static ssize_t ktest_read(struct file *file, char *buf, size_t buf_size,
eleni@0: 		loff_t *offset);
eleni@0: 
eleni@0: static int dev_num;
eleni@0: static struct file_operations ops = {
eleni@0: 	.open = ktest_open,
eleni@0: 	.release = ktest_release,
eleni@0: 	.read = ktest_read
eleni@0: };
eleni@0: static int hello_counter;
eleni@0: 
eleni@0: /* macros */
eleni@0: 
eleni@0: MODULE_LICENSE("GPL");
eleni@0: MODULE_AUTHOR("hikiko");
eleni@0: MODULE_DESCRIPTION("my kernel helloworld");
eleni@0: 
eleni@0: module_init(ktest_init);
eleni@0: module_exit(ktest_fini);
eleni@0: 
eleni@0: static int ktest_init(void)
eleni@0: {
eleni@0: 	hello_counter = 0;
eleni@0: 
eleni@0: 	/* register character device */
eleni@0: 	if((dev_num = register_chrdev(0, DEV_NAME, &ops)) < 0) {
eleni@0: 		printk(KERN_ALERT "Failed to register character device.\n");
eleni@0: 		return -1;
eleni@0: 	}
eleni@0: 	printk(KERN_INFO "Registered character device. Name: %s number: %d.\n", DEV_NAME, dev_num);
eleni@0: 	return 0;
eleni@0: }
eleni@0: 
eleni@0: static void ktest_fini(void)
eleni@0: {
eleni@0: 	unregister_chrdev(dev_num, DEV_NAME);
eleni@0: 	printk(KERN_INFO "Unregistered character device. Name: %s number: %d.\n", DEV_NAME, dev_num);
eleni@0: }
eleni@0: 
eleni@0: static int ktest_open(struct inode *inode, struct file *file)
eleni@0: {
eleni@0: 	/* 1 device file only => we ignore the params ^ */
eleni@0: 	try_module_get(THIS_MODULE);
eleni@0: 	return 0;
eleni@0: }
eleni@0: 
eleni@0: static int ktest_release(struct inode *inode, struct file *file)
eleni@0: {
eleni@0: 	module_put(THIS_MODULE);
eleni@0: 	return 0;
eleni@0: }
eleni@0: 
eleni@0: static ssize_t ktest_read(struct file *file, char *buf, size_t buf_size,
eleni@0: 		loff_t *offset)
eleni@0: {
eleni@0: 	/* buf = userspace buffer,
eleni@0: 	 * kbuf = kernel buffer */
eleni@0: 
eleni@0: 	char *kbuf;
eleni@0: 	int bytes;
eleni@0: 
eleni@0: 	if(!(kbuf = kmalloc(buf_size, GFP_KERNEL))) {
eleni@0: 		printk(KERN_ALERT "Failed to allocate memory.\n");
eleni@0: 		return -ENOMEM;
eleni@0: 	}
eleni@0: 
eleni@0: 	/* fill kbuf and copy to userspace buf */
eleni@0: 	bytes = snprintf(kbuf, buf_size, "Hello world, num: %d.\n", ++hello_counter);
eleni@0: 
eleni@0: 	if(copy_to_user(buf, kbuf, bytes))
eleni@0: 	{
eleni@0: 		kfree(kbuf);
eleni@0: 		return -EFAULT;
eleni@0: 	}
eleni@0: 
eleni@0: 	kfree(kbuf);
eleni@0: 	return bytes;
eleni@0: }