Line data Source code
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%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>
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 : */
57 : static LIST_HEAD(misc_list);
58 : static DEFINE_MUTEX(misc_mtx);
59 :
60 : /*
61 : * Assigned numbers, used for dynamic minors
62 : */
63 : #define DYNAMIC_MINORS 128 /* like dynamic majors */
64 : static DEFINE_IDA(misc_minors_ida);
65 :
66 1 : static int misc_minor_alloc(void)
67 : {
68 : int ret;
69 :
70 1 : ret = ida_alloc_max(&misc_minors_ida, DYNAMIC_MINORS - 1, GFP_KERNEL);
71 1 : if (ret >= 0) {
72 1 : ret = DYNAMIC_MINORS - ret - 1;
73 : } else {
74 0 : ret = ida_alloc_range(&misc_minors_ida, MISC_DYNAMIC_MINOR + 1,
75 : MINORMASK, GFP_KERNEL);
76 : }
77 1 : return ret;
78 : }
79 :
80 0 : static void misc_minor_free(int minor)
81 : {
82 0 : if (minor < DYNAMIC_MINORS)
83 0 : ida_free(&misc_minors_ida, DYNAMIC_MINORS - minor - 1);
84 0 : else if (minor > MISC_DYNAMIC_MINOR)
85 0 : ida_free(&misc_minors_ida, minor);
86 0 : }
87 :
88 : #ifdef CONFIG_PROC_FS
89 0 : static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
90 : {
91 0 : mutex_lock(&misc_mtx);
92 0 : return seq_list_start(&misc_list, *pos);
93 : }
94 :
95 0 : static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
96 : {
97 0 : return seq_list_next(v, &misc_list, pos);
98 : }
99 :
100 0 : static void misc_seq_stop(struct seq_file *seq, void *v)
101 : {
102 0 : mutex_unlock(&misc_mtx);
103 0 : }
104 :
105 0 : static int misc_seq_show(struct seq_file *seq, void *v)
106 : {
107 0 : const struct miscdevice *p = list_entry(v, struct miscdevice, list);
108 :
109 0 : seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
110 0 : return 0;
111 : }
112 :
113 :
114 : static const struct seq_operations misc_seq_ops = {
115 : .start = misc_seq_start,
116 : .next = misc_seq_next,
117 : .stop = misc_seq_stop,
118 : .show = misc_seq_show,
119 : };
120 : #endif
121 :
122 0 : static int misc_open(struct inode *inode, struct file *file)
123 : {
124 0 : int minor = iminor(inode);
125 0 : struct miscdevice *c = NULL, *iter;
126 0 : int err = -ENODEV;
127 0 : const struct file_operations *new_fops = NULL;
128 :
129 0 : mutex_lock(&misc_mtx);
130 :
131 0 : list_for_each_entry(iter, &misc_list, list) {
132 0 : if (iter->minor != minor)
133 0 : continue;
134 0 : c = iter;
135 0 : new_fops = fops_get(iter->fops);
136 : break;
137 : }
138 :
139 0 : if (!new_fops) {
140 0 : mutex_unlock(&misc_mtx);
141 0 : request_module("char-major-%d-%d", MISC_MAJOR, minor);
142 0 : mutex_lock(&misc_mtx);
143 :
144 0 : list_for_each_entry(iter, &misc_list, list) {
145 0 : if (iter->minor != minor)
146 0 : continue;
147 0 : c = iter;
148 0 : new_fops = fops_get(iter->fops);
149 : break;
150 : }
151 0 : if (!new_fops)
152 : goto fail;
153 : }
154 :
155 : /*
156 : * Place the miscdevice in the file's
157 : * private_data so it can be used by the
158 : * file operations, including f_op->open below
159 : */
160 0 : file->private_data = c;
161 :
162 0 : err = 0;
163 0 : replace_fops(file, new_fops);
164 0 : if (file->f_op->open)
165 0 : err = file->f_op->open(inode, file);
166 : fail:
167 0 : mutex_unlock(&misc_mtx);
168 0 : return err;
169 : }
170 :
171 : static struct class *misc_class;
172 :
173 : static const struct file_operations misc_fops = {
174 : .owner = THIS_MODULE,
175 : .open = misc_open,
176 : .llseek = noop_llseek,
177 : };
178 :
179 : /**
180 : * misc_register - register a miscellaneous device
181 : * @misc: device structure
182 : *
183 : * Register a miscellaneous device with the kernel. If the minor
184 : * number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
185 : * and placed in the minor field of the structure. For other cases
186 : * the minor number requested is used.
187 : *
188 : * The structure passed is linked into the kernel and may not be
189 : * destroyed until it has been unregistered. By default, an open()
190 : * syscall to the device sets file->private_data to point to the
191 : * structure. Drivers don't need open in fops for this.
192 : *
193 : * A zero is returned on success and a negative errno code for
194 : * failure.
195 : */
196 :
197 2 : int misc_register(struct miscdevice *misc)
198 : {
199 : dev_t dev;
200 2 : int err = 0;
201 2 : bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR);
202 :
203 4 : INIT_LIST_HEAD(&misc->list);
204 :
205 2 : mutex_lock(&misc_mtx);
206 :
207 2 : if (is_dynamic) {
208 1 : int i = misc_minor_alloc();
209 :
210 1 : if (i < 0) {
211 : err = -EBUSY;
212 : goto out;
213 : }
214 1 : misc->minor = i;
215 : } else {
216 : struct miscdevice *c;
217 :
218 2 : list_for_each_entry(c, &misc_list, list) {
219 1 : if (c->minor == misc->minor) {
220 : err = -EBUSY;
221 : goto out;
222 : }
223 : }
224 : }
225 :
226 2 : dev = MKDEV(MISC_MAJOR, misc->minor);
227 :
228 2 : misc->this_device =
229 2 : device_create_with_groups(misc_class, misc->parent, dev,
230 : misc, misc->groups, "%s", misc->name);
231 4 : if (IS_ERR(misc->this_device)) {
232 0 : if (is_dynamic) {
233 0 : misc_minor_free(misc->minor);
234 0 : misc->minor = MISC_DYNAMIC_MINOR;
235 : }
236 0 : err = PTR_ERR(misc->this_device);
237 0 : goto out;
238 : }
239 :
240 : /*
241 : * Add it to the front, so that later devices can "override"
242 : * earlier defaults
243 : */
244 2 : list_add(&misc->list, &misc_list);
245 : out:
246 2 : mutex_unlock(&misc_mtx);
247 2 : return err;
248 : }
249 : EXPORT_SYMBOL(misc_register);
250 :
251 : /**
252 : * misc_deregister - unregister a miscellaneous device
253 : * @misc: device to unregister
254 : *
255 : * Unregister a miscellaneous device that was previously
256 : * successfully registered with misc_register().
257 : */
258 :
259 0 : void misc_deregister(struct miscdevice *misc)
260 : {
261 0 : if (WARN_ON(list_empty(&misc->list)))
262 : return;
263 :
264 0 : mutex_lock(&misc_mtx);
265 0 : list_del(&misc->list);
266 0 : device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
267 0 : misc_minor_free(misc->minor);
268 0 : mutex_unlock(&misc_mtx);
269 : }
270 : EXPORT_SYMBOL(misc_deregister);
271 :
272 2 : static char *misc_devnode(const struct device *dev, umode_t *mode)
273 : {
274 2 : const struct miscdevice *c = dev_get_drvdata(dev);
275 :
276 2 : if (mode && c->mode)
277 0 : *mode = c->mode;
278 2 : if (c->nodename)
279 1 : return kstrdup(c->nodename, GFP_KERNEL);
280 : return NULL;
281 : }
282 :
283 1 : static int __init misc_init(void)
284 : {
285 : int err;
286 : struct proc_dir_entry *ret;
287 :
288 1 : ret = proc_create_seq("misc", 0, NULL, &misc_seq_ops);
289 1 : misc_class = class_create(THIS_MODULE, "misc");
290 2 : err = PTR_ERR(misc_class);
291 2 : if (IS_ERR(misc_class))
292 : goto fail_remove;
293 :
294 1 : err = -EIO;
295 1 : if (register_chrdev(MISC_MAJOR, "misc", &misc_fops))
296 : goto fail_printk;
297 1 : misc_class->devnode = misc_devnode;
298 1 : return 0;
299 :
300 : fail_printk:
301 0 : pr_err("unable to get major %d for misc devices\n", MISC_MAJOR);
302 0 : class_destroy(misc_class);
303 : fail_remove:
304 0 : if (ret)
305 0 : remove_proc_entry("misc", NULL);
306 : return err;
307 : }
308 : subsys_initcall(misc_init);
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