1/*
2 * linux/drivers/char/misc.c
3 *
4 * Generic misc open routine by Johan Myreen
5 *
6 * Based on code from Linus
7 *
8 * Teemu Rantanen's Microsoft Busmouse support and Derrick Cole's
9 *   changes incorporated into 0.97pl4
10 *   by Peter Cervasio (pete%q106fm.uucp@wupost.wustl.edu) (08SEP92)
11 *   See busmouse.c for particulars.
12 *
13 * Made things a lot mode modular - easy to compile in just one or two
14 * of the misc drivers, as they are now completely independent. Linus.
15 *
16 * Support for loadable modules. 8-Sep-95 Philip Blundell <pjb27@cam.ac.uk>
17 *
18 * Fixed a failing symbol register to free the device registration
19 *		Alan Cox <alan@lxorguk.ukuu.org.uk> 21-Jan-96
20 *
21 * Dynamic minors and /proc/mice by Alessandro Rubini. 26-Mar-96
22 *
23 * Renamed to misc and miscdevice to be more accurate. Alan Cox 26-Mar-96
24 *
25 * Handling of mouse minor numbers for kerneld:
26 *  Idea by Jacques Gelinas <jack@solucorp.qc.ca>,
27 *  adapted by Bjorn Ekwall <bj0rn@blox.se>
28 *  corrected by Alan Cox <alan@lxorguk.ukuu.org.uk>
29 *
30 * Changes for kmod (from kerneld):
31 *	Cyrus Durgin <cider@speakeasy.org>
32 *
33 * Added devfs support. Richard Gooch <rgooch@atnf.csiro.au>  10-Jan-1998
34 */
35
36#include <linux/module.h>
37
38#include <linux/fs.h>
39#include <linux/errno.h>
40#include <linux/miscdevice.h>
41#include <linux/kernel.h>
42#include <linux/major.h>
43#include <linux/mutex.h>
44#include <linux/proc_fs.h>
45#include <linux/seq_file.h>
46#include <linux/stat.h>
47#include <linux/init.h>
48#include <linux/device.h>
49#include <linux/tty.h>
50#include <linux/kmod.h>
51#include <linux/gfp.h>
52
53/*
54 * Head entry for the doubly linked miscdevice list
55 */
56static LIST_HEAD(misc_list);
57static DEFINE_MUTEX(misc_mtx);
58
59/*
60 * Assigned numbers, used for dynamic minors
61 */
62#define DYNAMIC_MINORS 64 /* like dynamic majors */
63static DECLARE_BITMAP(misc_minors, DYNAMIC_MINORS);
64
65#ifdef CONFIG_PROC_FS
66static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
67{
68	mutex_lock(&misc_mtx);
69	return seq_list_start(&misc_list, *pos);
70}
71
72static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
73{
74	return seq_list_next(v, &misc_list, pos);
75}
76
77static void misc_seq_stop(struct seq_file *seq, void *v)
78{
79	mutex_unlock(&misc_mtx);
80}
81
82static int misc_seq_show(struct seq_file *seq, void *v)
83{
84	const struct miscdevice *p = list_entry(v, struct miscdevice, list);
85
86	seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
87	return 0;
88}
89
90
91static const struct seq_operations misc_seq_ops = {
92	.start = misc_seq_start,
93	.next  = misc_seq_next,
94	.stop  = misc_seq_stop,
95	.show  = misc_seq_show,
96};
97
98static int misc_seq_open(struct inode *inode, struct file *file)
99{
100	return seq_open(file, &misc_seq_ops);
101}
102
103static const struct file_operations misc_proc_fops = {
104	.owner	 = THIS_MODULE,
105	.open    = misc_seq_open,
106	.read    = seq_read,
107	.llseek  = seq_lseek,
108	.release = seq_release,
109};
110#endif
111
112static int misc_open(struct inode * inode, struct file * file)
113{
114	int minor = iminor(inode);
115	struct miscdevice *c;
116	int err = -ENODEV;
117	const struct file_operations *new_fops = NULL;
118
119	mutex_lock(&misc_mtx);
120
121	list_for_each_entry(c, &misc_list, list) {
122		if (c->minor == minor) {
123			new_fops = fops_get(c->fops);
124			break;
125		}
126	}
127
128	if (!new_fops) {
129		mutex_unlock(&misc_mtx);
130		request_module("char-major-%d-%d", MISC_MAJOR, minor);
131		mutex_lock(&misc_mtx);
132
133		list_for_each_entry(c, &misc_list, list) {
134			if (c->minor == minor) {
135				new_fops = fops_get(c->fops);
136				break;
137			}
138		}
139		if (!new_fops)
140			goto fail;
141	}
142
143	/*
144	 * Place the miscdevice in the file's
145	 * private_data so it can be used by the
146	 * file operations, including f_op->open below
147	 */
148	file->private_data = c;
149
150	err = 0;
151	replace_fops(file, new_fops);
152	if (file->f_op->open)
153		err = file->f_op->open(inode,file);
154fail:
155	mutex_unlock(&misc_mtx);
156	return err;
157}
158
159static struct class *misc_class;
160
161static const struct file_operations misc_fops = {
162	.owner		= THIS_MODULE,
163	.open		= misc_open,
164	.llseek		= noop_llseek,
165};
166
167/**
168 *	misc_register	-	register a miscellaneous device
169 *	@misc: device structure
170 *
171 *	Register a miscellaneous device with the kernel. If the minor
172 *	number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
173 *	and placed in the minor field of the structure. For other cases
174 *	the minor number requested is used.
175 *
176 *	The structure passed is linked into the kernel and may not be
177 *	destroyed until it has been unregistered. By default, an open()
178 *	syscall to the device sets file->private_data to point to the
179 *	structure. Drivers don't need open in fops for this.
180 *
181 *	A zero is returned on success and a negative errno code for
182 *	failure.
183 */
184
185int misc_register(struct miscdevice * misc)
186{
187	dev_t dev;
188	int err = 0;
189
190	INIT_LIST_HEAD(&misc->list);
191
192	mutex_lock(&misc_mtx);
193
194	if (misc->minor == MISC_DYNAMIC_MINOR) {
195		int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS);
196		if (i >= DYNAMIC_MINORS) {
197			err = -EBUSY;
198			goto out;
199		}
200		misc->minor = DYNAMIC_MINORS - i - 1;
201		set_bit(i, misc_minors);
202	} else {
203		struct miscdevice *c;
204
205		list_for_each_entry(c, &misc_list, list) {
206			if (c->minor == misc->minor) {
207				err = -EBUSY;
208				goto out;
209			}
210		}
211	}
212
213	dev = MKDEV(MISC_MAJOR, misc->minor);
214
215	misc->this_device =
216		device_create_with_groups(misc_class, misc->parent, dev,
217					  misc, misc->groups, "%s", misc->name);
218	if (IS_ERR(misc->this_device)) {
219		int i = DYNAMIC_MINORS - misc->minor - 1;
220		if (i < DYNAMIC_MINORS && i >= 0)
221			clear_bit(i, misc_minors);
222		err = PTR_ERR(misc->this_device);
223		goto out;
224	}
225
226	/*
227	 * Add it to the front, so that later devices can "override"
228	 * earlier defaults
229	 */
230	list_add(&misc->list, &misc_list);
231 out:
232	mutex_unlock(&misc_mtx);
233	return err;
234}
235
236/**
237 *	misc_deregister - unregister a miscellaneous device
238 *	@misc: device to unregister
239 *
240 *	Unregister a miscellaneous device that was previously
241 *	successfully registered with misc_register(). Success
242 *	is indicated by a zero return, a negative errno code
243 *	indicates an error.
244 */
245
246int misc_deregister(struct miscdevice *misc)
247{
248	int i = DYNAMIC_MINORS - misc->minor - 1;
249
250	if (WARN_ON(list_empty(&misc->list)))
251		return -EINVAL;
252
253	mutex_lock(&misc_mtx);
254	list_del(&misc->list);
255	device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
256	if (i < DYNAMIC_MINORS && i >= 0)
257		clear_bit(i, misc_minors);
258	mutex_unlock(&misc_mtx);
259	return 0;
260}
261
262EXPORT_SYMBOL(misc_register);
263EXPORT_SYMBOL(misc_deregister);
264
265static char *misc_devnode(struct device *dev, umode_t *mode)
266{
267	struct miscdevice *c = dev_get_drvdata(dev);
268
269	if (mode && c->mode)
270		*mode = c->mode;
271	if (c->nodename)
272		return kstrdup(c->nodename, GFP_KERNEL);
273	return NULL;
274}
275
276static int __init misc_init(void)
277{
278	int err;
279
280#ifdef CONFIG_PROC_FS
281	proc_create("misc", 0, NULL, &misc_proc_fops);
282#endif
283	misc_class = class_create(THIS_MODULE, "misc");
284	err = PTR_ERR(misc_class);
285	if (IS_ERR(misc_class))
286		goto fail_remove;
287
288	err = -EIO;
289	if (register_chrdev(MISC_MAJOR,"misc",&misc_fops))
290		goto fail_printk;
291	misc_class->devnode = misc_devnode;
292	return 0;
293
294fail_printk:
295	printk("unable to get major %d for misc devices\n", MISC_MAJOR);
296	class_destroy(misc_class);
297fail_remove:
298	remove_proc_entry("misc", NULL);
299	return err;
300}
301subsys_initcall(misc_init);
302