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1// SPDX-License-Identifier: GPL-2.0
2/*
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%[email protected]) (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 <[email protected]>
18 *
19 * Fixed a failing symbol register to free the device registration
20 * Alan Cox <[email protected]> 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 <[email protected]>,
28 * adapted by Bjorn Ekwall <[email protected]>
29 * corrected by Alan Cox <[email protected]>
30 *
31 * Changes for kmod (from kerneld):
32 * Cyrus Durgin <[email protected]>
33 *
34 * Added devfs support. Richard Gooch <[email protected]> 10-Jan-1998
35 */
36
37#include <linux/module.h>
38
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>
44#include <linux/mutex.h>
45#include <linux/proc_fs.h>
46#include <linux/seq_file.h>
47#include <linux/stat.h>
48#include <linux/init.h>
49#include <linux/device.h>
50#include <linux/tty.h>
51#include <linux/kmod.h>
52#include <linux/gfp.h>
53
54/*
55 * Head entry for the doubly linked miscdevice list
56 */
57static LIST_HEAD(misc_list);
58static DEFINE_MUTEX(misc_mtx);
59
60/*
61 * Assigned numbers.
62 */
63static DEFINE_IDA(misc_minors_ida);
64
65static int misc_minor_alloc(int minor)
66{
67 int ret = 0;
68
69 if (minor == MISC_DYNAMIC_MINOR) {
70 /* allocate free id */
71 ret = ida_alloc_range(&misc_minors_ida, MISC_DYNAMIC_MINOR + 1,
72 MINORMASK, GFP_KERNEL);
73 } else {
74 ret = ida_alloc_range(&misc_minors_ida, minor, minor, GFP_KERNEL);
75 }
76 return ret;
77}
78
79static void misc_minor_free(int minor)
80{
81 ida_free(&misc_minors_ida, minor);
82}
83
84#ifdef CONFIG_PROC_FS
85static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
86{
87 mutex_lock(&misc_mtx);
88 return seq_list_start(&misc_list, *pos);
89}
90
91static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
92{
93 return seq_list_next(v, &misc_list, pos);
94}
95
96static void misc_seq_stop(struct seq_file *seq, void *v)
97{
98 mutex_unlock(&misc_mtx);
99}
100
101static int misc_seq_show(struct seq_file *seq, void *v)
102{
103 const struct miscdevice *p = list_entry(v, struct miscdevice, list);
104
105 seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
106 return 0;
107}
108
109
110static const struct seq_operations misc_seq_ops = {
111 .start = misc_seq_start,
112 .next = misc_seq_next,
113 .stop = misc_seq_stop,
114 .show = misc_seq_show,
115};
116#endif
117
118static int misc_open(struct inode *inode, struct file *file)
119{
120 int minor = iminor(inode);
121 struct miscdevice *c = NULL, *iter;
122 int err = -ENODEV;
123 const struct file_operations *new_fops = NULL;
124
125 mutex_lock(&misc_mtx);
126
127 list_for_each_entry(iter, &misc_list, list) {
128 if (iter->minor != minor)
129 continue;
130 c = iter;
131 new_fops = fops_get(iter->fops);
132 break;
133 }
134
135 /* Only request module for fixed minor code */
136 if (!new_fops && minor < MISC_DYNAMIC_MINOR) {
137 mutex_unlock(&misc_mtx);
138 request_module("char-major-%d-%d", MISC_MAJOR, minor);
139 mutex_lock(&misc_mtx);
140
141 list_for_each_entry(iter, &misc_list, list) {
142 if (iter->minor != minor)
143 continue;
144 c = iter;
145 new_fops = fops_get(iter->fops);
146 break;
147 }
148 }
149
150 if (!new_fops)
151 goto fail;
152
153 /*
154 * Place the miscdevice in the file's
155 * private_data so it can be used by the
156 * file operations, including f_op->open below
157 */
158 file->private_data = c;
159
160 err = 0;
161 replace_fops(file, new_fops);
162 if (file->f_op->open)
163 err = file->f_op->open(inode, file);
164fail:
165 mutex_unlock(&misc_mtx);
166 return err;
167}
168
169static char *misc_devnode(const struct device *dev, umode_t *mode)
170{
171 const struct miscdevice *c = dev_get_drvdata(dev);
172
173 if (mode && c->mode)
174 *mode = c->mode;
175 if (c->nodename)
176 return kstrdup(c->nodename, GFP_KERNEL);
177 return NULL;
178}
179
180static const struct class misc_class = {
181 .name = "misc",
182 .devnode = misc_devnode,
183};
184
185static const struct file_operations misc_fops = {
186 .owner = THIS_MODULE,
187 .open = misc_open,
188 .llseek = noop_llseek,
189};
190
191/**
192 * misc_register - register a miscellaneous device
193 * @misc: device structure
194 *
195 * Register a miscellaneous device with the kernel. If the minor
196 * number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
197 * and placed in the minor field of the structure. For other cases
198 * the minor number requested is used.
199 *
200 * The structure passed is linked into the kernel and may not be
201 * destroyed until it has been unregistered. By default, an open()
202 * syscall to the device sets file->private_data to point to the
203 * structure. Drivers don't need open in fops for this.
204 *
205 * A zero is returned on success and a negative errno code for
206 * failure.
207 */
208
209int misc_register(struct miscdevice *misc)
210{
211 dev_t dev;
212 int err = 0;
213 bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR);
214
215 if (misc->minor > MISC_DYNAMIC_MINOR) {
216 pr_err("Invalid fixed minor %d for miscdevice '%s'\n",
217 misc->minor, misc->name);
218 return -EINVAL;
219 }
220
221 INIT_LIST_HEAD(&misc->list);
222
223 mutex_lock(&misc_mtx);
224
225 if (is_dynamic) {
226 int i = misc_minor_alloc(misc->minor);
227
228 if (i < 0) {
229 err = -EBUSY;
230 goto out;
231 }
232 misc->minor = i;
233 } else {
234 struct miscdevice *c;
235 int i;
236
237 list_for_each_entry(c, &misc_list, list) {
238 if (c->minor == misc->minor) {
239 err = -EBUSY;
240 goto out;
241 }
242 }
243
244 i = misc_minor_alloc(misc->minor);
245 if (i < 0) {
246 err = -EBUSY;
247 goto out;
248 }
249 }
250
251 dev = MKDEV(MISC_MAJOR, misc->minor);
252
253 misc->this_device =
254 device_create_with_groups(&misc_class, misc->parent, dev,
255 misc, misc->groups, "%s", misc->name);
256 if (IS_ERR(misc->this_device)) {
257 misc_minor_free(misc->minor);
258 if (is_dynamic) {
259 misc->minor = MISC_DYNAMIC_MINOR;
260 }
261 err = PTR_ERR(misc->this_device);
262 goto out;
263 }
264
265 /*
266 * Add it to the front, so that later devices can "override"
267 * earlier defaults
268 */
269 list_add(&misc->list, &misc_list);
270 out:
271 mutex_unlock(&misc_mtx);
272 return err;
273}
274EXPORT_SYMBOL(misc_register);
275
276/**
277 * misc_deregister - unregister a miscellaneous device
278 * @misc: device to unregister
279 *
280 * Unregister a miscellaneous device that was previously
281 * successfully registered with misc_register().
282 */
283
284void misc_deregister(struct miscdevice *misc)
285{
286 mutex_lock(&misc_mtx);
287 list_del_init(&misc->list);
288 device_destroy(&misc_class, MKDEV(MISC_MAJOR, misc->minor));
289 misc_minor_free(misc->minor);
290 if (misc->minor > MISC_DYNAMIC_MINOR)
291 misc->minor = MISC_DYNAMIC_MINOR;
292 mutex_unlock(&misc_mtx);
293}
294EXPORT_SYMBOL(misc_deregister);
295
296static int __init misc_init(void)
297{
298 int err;
299 struct proc_dir_entry *misc_proc_file;
300
301 misc_proc_file = proc_create_seq("misc", 0, NULL, &misc_seq_ops);
302 err = class_register(&misc_class);
303 if (err)
304 goto fail_remove;
305
306 err = __register_chrdev(MISC_MAJOR, 0, MINORMASK + 1, "misc", &misc_fops);
307 if (err < 0)
308 goto fail_printk;
309 return 0;
310
311fail_printk:
312 pr_err("unable to get major %d for misc devices\n", MISC_MAJOR);
313 class_unregister(&misc_class);
314fail_remove:
315 if (misc_proc_file)
316 remove_proc_entry("misc", NULL);
317 return err;
318}
319subsys_initcall(misc_init);