2 * Copyright (C) 2010 Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
4 * This program is free software; you can redistribute it and/or modify
5 * it under the terms of the GNU General Public License as published by
6 * the Free Software Foundation; either version 2 of the License, or
7 * (at your option) any later version.
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 * GNU General Public License for more details.
14 * You should have received a copy of the GNU General Public License along
15 * with this program; if not, write to the Free Software Foundation, Inc.,
16 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
19 #include <linux/module.h>
21 #include <linux/cdev.h>
22 #include <linux/slab.h>
23 #include <asm/uaccess.h>
25 MODULE_LICENSE("GPL");
29 static struct cdev *dev;
30 static const char default_greeting[] = "Hello, World!\n";
37 static int hello_open(struct inode *ino, struct file *fp)
39 struct hello_buffer *hello = kzalloc(sizeof(*hello) + MAXLEN, GFP_KERNEL);
42 memcpy(hello->buffer, default_greeting, sizeof(default_greeting));
43 hello->len = sizeof(default_greeting);
44 fp->private_data = hello;
48 static ssize_t hello_read(struct file *fp, char __user *buf, size_t sz,
51 struct hello_buffer *hello = fp->private_data;
53 if (sz + *pos > hello->len)
54 sz = hello->len - *pos;
55 r = copy_to_user(buf, hello->buffer + *pos, sz);
62 static ssize_t hello_write(struct file *fp, const char __user *buf, size_t sz,
65 struct hello_buffer *hello = fp->private_data;
67 if (sz + *pos > MAXLEN)
69 r = copy_from_user(hello->buffer + *pos, buf, sz);
73 if (hello->len < *pos)
78 static int hello_release(struct inode *ino, struct file *fp)
80 kfree(fp->private_data);
84 static const struct file_operations hello_fops = {
87 .release = hello_release,
92 static int __init ch_init(void)
95 r = alloc_chrdev_region(&devnum, 0, 256, "hello");
103 dev->ops = &hello_fops;
104 r = cdev_add(dev, devnum, 256);
107 printk(KERN_DEBUG "Allocate major %d\n", MAJOR(devnum));
112 unregister_chrdev_region(devnum, 256);
117 static void __exit ch_exit(void)
120 unregister_chrdev_region(devnum, 256);
123 module_init(ch_init);
124 module_exit(ch_exit);