blob: 53cfe574d8d4b647f378e602c44e663e401b772e [file] [log] [blame]
Greg Kroah-Hartmanb2441312017-11-01 15:07:57 +01001// SPDX-License-Identifier: GPL-2.0
Linus Torvalds1da177e2005-04-16 15:20:36 -07002/*
3 * linux/drivers/char/misc.c
4 *
5 * Generic misc open routine by Johan Myreen
6 *
7 * Based on code from Linus
8 *
9 * Teemu Rantanen's Microsoft Busmouse support and Derrick Cole's
10 * changes incorporated into 0.97pl4
11 * by Peter Cervasio (pete%q106fm.uucp@wupost.wustl.edu) (08SEP92)
12 * See busmouse.c for particulars.
13 *
14 * Made things a lot mode modular - easy to compile in just one or two
15 * of the misc drivers, as they are now completely independent. Linus.
16 *
17 * Support for loadable modules. 8-Sep-95 Philip Blundell <pjb27@cam.ac.uk>
18 *
19 * Fixed a failing symbol register to free the device registration
20 * Alan Cox <alan@lxorguk.ukuu.org.uk> 21-Jan-96
21 *
22 * Dynamic minors and /proc/mice by Alessandro Rubini. 26-Mar-96
23 *
24 * Renamed to misc and miscdevice to be more accurate. Alan Cox 26-Mar-96
25 *
26 * Handling of mouse minor numbers for kerneld:
27 * Idea by Jacques Gelinas <jack@solucorp.qc.ca>,
28 * adapted by Bjorn Ekwall <bj0rn@blox.se>
29 * corrected by Alan Cox <alan@lxorguk.ukuu.org.uk>
30 *
31 * Changes for kmod (from kerneld):
32 * Cyrus Durgin <cider@speakeasy.org>
33 *
34 * Added devfs support. Richard Gooch <rgooch@atnf.csiro.au> 10-Jan-1998
35 */
36
37#include <linux/module.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070038
39#include <linux/fs.h>
40#include <linux/errno.h>
41#include <linux/miscdevice.h>
42#include <linux/kernel.h>
43#include <linux/major.h>
Matthias Kaehlcke0e82d5b2007-05-08 00:32:08 -070044#include <linux/mutex.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070045#include <linux/proc_fs.h>
46#include <linux/seq_file.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070047#include <linux/stat.h>
48#include <linux/init.h>
49#include <linux/device.h>
50#include <linux/tty.h>
51#include <linux/kmod.h>
Tejun Heo5a0e3ad2010-03-24 17:04:11 +090052#include <linux/gfp.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070053
54/*
55 * Head entry for the doubly linked miscdevice list
56 */
57static LIST_HEAD(misc_list);
Matthias Kaehlcke0e82d5b2007-05-08 00:32:08 -070058static DEFINE_MUTEX(misc_mtx);
Linus Torvalds1da177e2005-04-16 15:20:36 -070059
60/*
61 * Assigned numbers, used for dynamic minors
62 */
63#define DYNAMIC_MINORS 64 /* like dynamic majors */
Thadeu Lima de Souza Cascardo1f2f38d2009-12-14 18:00:31 -080064static DECLARE_BITMAP(misc_minors, DYNAMIC_MINORS);
Linus Torvalds1da177e2005-04-16 15:20:36 -070065
Linus Torvalds1da177e2005-04-16 15:20:36 -070066#ifdef CONFIG_PROC_FS
67static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
68{
Matthias Kaehlcke0e82d5b2007-05-08 00:32:08 -070069 mutex_lock(&misc_mtx);
Pavel Emelianov46c65b72007-07-15 23:39:53 -070070 return seq_list_start(&misc_list, *pos);
Linus Torvalds1da177e2005-04-16 15:20:36 -070071}
72
73static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
74{
Pavel Emelianov46c65b72007-07-15 23:39:53 -070075 return seq_list_next(v, &misc_list, pos);
Linus Torvalds1da177e2005-04-16 15:20:36 -070076}
77
78static void misc_seq_stop(struct seq_file *seq, void *v)
79{
Matthias Kaehlcke0e82d5b2007-05-08 00:32:08 -070080 mutex_unlock(&misc_mtx);
Linus Torvalds1da177e2005-04-16 15:20:36 -070081}
82
83static int misc_seq_show(struct seq_file *seq, void *v)
84{
Pavel Emelianov46c65b72007-07-15 23:39:53 -070085 const struct miscdevice *p = list_entry(v, struct miscdevice, list);
Linus Torvalds1da177e2005-04-16 15:20:36 -070086
87 seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
88 return 0;
89}
90
91
James Morris88e9d342009-09-22 16:43:43 -070092static const struct seq_operations misc_seq_ops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -070093 .start = misc_seq_start,
94 .next = misc_seq_next,
95 .stop = misc_seq_stop,
96 .show = misc_seq_show,
97};
Linus Torvalds1da177e2005-04-16 15:20:36 -070098#endif
99
Varsha Rao65ebd3d2017-04-07 16:58:54 +0530100static int misc_open(struct inode *inode, struct file *file)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700101{
102 int minor = iminor(inode);
103 struct miscdevice *c;
104 int err = -ENODEV;
Al Viroe84f9e52013-09-22 14:17:15 -0400105 const struct file_operations *new_fops = NULL;
Thomas Gleixner40b798e2009-10-10 15:35:43 +0000106
Matthias Kaehlcke0e82d5b2007-05-08 00:32:08 -0700107 mutex_lock(&misc_mtx);
Tal Shorer898bc282015-05-01 14:53:09 +0300108
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109 list_for_each_entry(c, &misc_list, list) {
110 if (c->minor == minor) {
Tal Shorer898bc282015-05-01 14:53:09 +0300111 new_fops = fops_get(c->fops);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700112 break;
113 }
114 }
Tal Shorer898bc282015-05-01 14:53:09 +0300115
Linus Torvalds1da177e2005-04-16 15:20:36 -0700116 if (!new_fops) {
Matthias Kaehlcke0e82d5b2007-05-08 00:32:08 -0700117 mutex_unlock(&misc_mtx);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118 request_module("char-major-%d-%d", MISC_MAJOR, minor);
Matthias Kaehlcke0e82d5b2007-05-08 00:32:08 -0700119 mutex_lock(&misc_mtx);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700120
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 if (!new_fops)
128 goto fail;
129 }
130
Tom Van Braeckel0b509d82015-03-31 16:39:21 +0200131 /*
132 * Place the miscdevice in the file's
133 * private_data so it can be used by the
134 * file operations, including f_op->open below
135 */
136 file->private_data = c;
137
Linus Torvalds1da177e2005-04-16 15:20:36 -0700138 err = 0;
Al Viroe84f9e52013-09-22 14:17:15 -0400139 replace_fops(file, new_fops);
Tom Van Braeckel0b509d82015-03-31 16:39:21 +0200140 if (file->f_op->open)
Varsha Rao50a5e3142017-04-07 17:01:31 +0530141 err = file->f_op->open(inode, file);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700142fail:
Matthias Kaehlcke0e82d5b2007-05-08 00:32:08 -0700143 mutex_unlock(&misc_mtx);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700144 return err;
145}
146
gregkh@suse.deca8eca62005-03-23 09:53:09 -0800147static struct class *misc_class;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700148
Arjan van de Ven62322d22006-07-03 00:24:21 -0700149static const struct file_operations misc_fops = {
Linus Torvalds1da177e2005-04-16 15:20:36 -0700150 .owner = THIS_MODULE,
151 .open = misc_open,
Arnd Bergmann6038f372010-08-15 18:52:59 +0200152 .llseek = noop_llseek,
Linus Torvalds1da177e2005-04-16 15:20:36 -0700153};
154
Linus Torvalds1da177e2005-04-16 15:20:36 -0700155/**
156 * misc_register - register a miscellaneous device
157 * @misc: device structure
Tal Shorer898bc282015-05-01 14:53:09 +0300158 *
Linus Torvalds1da177e2005-04-16 15:20:36 -0700159 * Register a miscellaneous device with the kernel. If the minor
160 * number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
161 * and placed in the minor field of the structure. For other cases
162 * the minor number requested is used.
163 *
164 * The structure passed is linked into the kernel and may not be
Martin Kepplinger03190c62015-03-23 13:59:46 +0100165 * destroyed until it has been unregistered. By default, an open()
166 * syscall to the device sets file->private_data to point to the
167 * structure. Drivers don't need open in fops for this.
Linus Torvalds1da177e2005-04-16 15:20:36 -0700168 *
169 * A zero is returned on success and a negative errno code for
170 * failure.
171 */
Tal Shorer898bc282015-05-01 14:53:09 +0300172
Varsha Rao65ebd3d2017-04-07 16:58:54 +0530173int misc_register(struct miscdevice *misc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700174{
Linus Torvalds1da177e2005-04-16 15:20:36 -0700175 dev_t dev;
Greg Kroah-Hartman7c69ef72005-06-20 21:15:16 -0700176 int err = 0;
Vladimir Zapolskiyb575f712015-05-18 20:11:46 +0300177 bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700178
Neil Horman5d469ec02006-12-06 20:37:08 -0800179 INIT_LIST_HEAD(&misc->list);
180
Matthias Kaehlcke0e82d5b2007-05-08 00:32:08 -0700181 mutex_lock(&misc_mtx);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700182
Vladimir Zapolskiyb575f712015-05-18 20:11:46 +0300183 if (is_dynamic) {
Thadeu Lima de Souza Cascardo1f2f38d2009-12-14 18:00:31 -0800184 int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS);
Varsha Rao5b884a92017-04-07 17:02:32 +0530185
Thadeu Lima de Souza Cascardo1f2f38d2009-12-14 18:00:31 -0800186 if (i >= DYNAMIC_MINORS) {
Elad Wexler684116c2013-09-14 18:02:11 +0300187 err = -EBUSY;
188 goto out;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700189 }
Thadeu Lima de Souza Cascardo1f2f38d2009-12-14 18:00:31 -0800190 misc->minor = DYNAMIC_MINORS - i - 1;
191 set_bit(i, misc_minors);
Dae S. Kim3c94ce62013-02-27 17:05:14 -0800192 } else {
193 struct miscdevice *c;
194
195 list_for_each_entry(c, &misc_list, list) {
196 if (c->minor == misc->minor) {
Elad Wexler684116c2013-09-14 18:02:11 +0300197 err = -EBUSY;
198 goto out;
Dae S. Kim3c94ce62013-02-27 17:05:14 -0800199 }
200 }
Linus Torvalds1da177e2005-04-16 15:20:36 -0700201 }
202
Linus Torvalds1da177e2005-04-16 15:20:36 -0700203 dev = MKDEV(MISC_MAJOR, misc->minor);
204
Takashi Iwaibd735992015-02-02 15:44:54 +0100205 misc->this_device =
206 device_create_with_groups(misc_class, misc->parent, dev,
207 misc, misc->groups, "%s", misc->name);
Greg Kroah-Hartman94fbcde2006-07-27 16:16:04 -0700208 if (IS_ERR(misc->this_device)) {
Vladimir Zapolskiyb575f712015-05-18 20:11:46 +0300209 if (is_dynamic) {
210 int i = DYNAMIC_MINORS - misc->minor - 1;
211
212 if (i < DYNAMIC_MINORS && i >= 0)
213 clear_bit(i, misc_minors);
214 misc->minor = MISC_DYNAMIC_MINOR;
215 }
Greg Kroah-Hartman94fbcde2006-07-27 16:16:04 -0700216 err = PTR_ERR(misc->this_device);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700217 goto out;
218 }
219
Linus Torvalds1da177e2005-04-16 15:20:36 -0700220 /*
221 * Add it to the front, so that later devices can "override"
222 * earlier defaults
223 */
224 list_add(&misc->list, &misc_list);
225 out:
Matthias Kaehlcke0e82d5b2007-05-08 00:32:08 -0700226 mutex_unlock(&misc_mtx);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700227 return err;
228}
229
230/**
Rafael J. Wysockib844eba2008-03-23 20:28:24 +0100231 * misc_deregister - unregister a miscellaneous device
Linus Torvalds1da177e2005-04-16 15:20:36 -0700232 * @misc: device to unregister
233 *
234 * Unregister a miscellaneous device that was previously
Greg Kroah-Hartmanf368ed62015-07-30 15:59:57 -0700235 * successfully registered with misc_register().
Linus Torvalds1da177e2005-04-16 15:20:36 -0700236 */
237
Greg Kroah-Hartmanf368ed62015-07-30 15:59:57 -0700238void misc_deregister(struct miscdevice *misc)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700239{
Thadeu Lima de Souza Cascardo1f2f38d2009-12-14 18:00:31 -0800240 int i = DYNAMIC_MINORS - misc->minor - 1;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700241
Akinobu Mitab329bec2010-08-09 17:20:35 -0700242 if (WARN_ON(list_empty(&misc->list)))
Greg Kroah-Hartmanf368ed62015-07-30 15:59:57 -0700243 return;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700244
Matthias Kaehlcke0e82d5b2007-05-08 00:32:08 -0700245 mutex_lock(&misc_mtx);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700246 list_del(&misc->list);
Rafael J. Wysockib844eba2008-03-23 20:28:24 +0100247 device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
Thadeu Lima de Souza Cascardo4ae717d2009-12-14 18:00:30 -0800248 if (i < DYNAMIC_MINORS && i >= 0)
Thadeu Lima de Souza Cascardo1f2f38d2009-12-14 18:00:31 -0800249 clear_bit(i, misc_minors);
Matthias Kaehlcke0e82d5b2007-05-08 00:32:08 -0700250 mutex_unlock(&misc_mtx);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700251}
252
253EXPORT_SYMBOL(misc_register);
Rafael J. Wysockib844eba2008-03-23 20:28:24 +0100254EXPORT_SYMBOL(misc_deregister);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700255
Al Viro2c9ede52011-07-23 20:24:48 -0400256static char *misc_devnode(struct device *dev, umode_t *mode)
Kay Sieversd4056402009-04-30 15:23:42 +0200257{
258 struct miscdevice *c = dev_get_drvdata(dev);
259
Kay Sieverse454cea2009-09-18 23:01:12 +0200260 if (mode && c->mode)
261 *mode = c->mode;
262 if (c->nodename)
263 return kstrdup(c->nodename, GFP_KERNEL);
Kay Sieversd4056402009-04-30 15:23:42 +0200264 return NULL;
265}
266
Linus Torvalds1da177e2005-04-16 15:20:36 -0700267static int __init misc_init(void)
268{
Denis V. Lunev1b502212008-04-29 01:02:34 -0700269 int err;
Sudip Mukherjee1037b2782015-07-13 17:32:28 +0530270 struct proc_dir_entry *ret;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700271
Christoph Hellwigfddda2b2018-04-13 19:44:18 +0200272 ret = proc_create_seq("misc", 0, NULL, &misc_seq_ops);
gregkh@suse.deca8eca62005-03-23 09:53:09 -0800273 misc_class = class_create(THIS_MODULE, "misc");
Denis V. Lunev1b502212008-04-29 01:02:34 -0700274 err = PTR_ERR(misc_class);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700275 if (IS_ERR(misc_class))
Denis V. Lunev1b502212008-04-29 01:02:34 -0700276 goto fail_remove;
Christoph Hellwig573fc112005-09-06 15:16:58 -0700277
Denis V. Lunev1b502212008-04-29 01:02:34 -0700278 err = -EIO;
Varsha Rao50a5e3142017-04-07 17:01:31 +0530279 if (register_chrdev(MISC_MAJOR, "misc", &misc_fops))
Denis V. Lunev1b502212008-04-29 01:02:34 -0700280 goto fail_printk;
Kay Sieverse454cea2009-09-18 23:01:12 +0200281 misc_class->devnode = misc_devnode;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700282 return 0;
Denis V. Lunev1b502212008-04-29 01:02:34 -0700283
284fail_printk:
Varsha Rao8ab44b42017-04-07 17:04:06 +0530285 pr_err("unable to get major %d for misc devices\n", MISC_MAJOR);
Denis V. Lunev1b502212008-04-29 01:02:34 -0700286 class_destroy(misc_class);
287fail_remove:
Sudip Mukherjee1037b2782015-07-13 17:32:28 +0530288 if (ret)
289 remove_proc_entry("misc", NULL);
Denis V. Lunev1b502212008-04-29 01:02:34 -0700290 return err;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700291}
292subsys_initcall(misc_init);