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 | static int misc_minor_alloc(void) |
67 | { |
68 | int ret; |
69 | |
70 | ret = ida_alloc_max(ida: &misc_minors_ida, DYNAMIC_MINORS - 1, GFP_KERNEL); |
71 | if (ret >= 0) { |
72 | ret = DYNAMIC_MINORS - ret - 1; |
73 | } else { |
74 | ret = ida_alloc_range(&misc_minors_ida, MISC_DYNAMIC_MINOR + 1, |
75 | MINORMASK, GFP_KERNEL); |
76 | } |
77 | return ret; |
78 | } |
79 | |
80 | static void misc_minor_free(int minor) |
81 | { |
82 | if (minor < DYNAMIC_MINORS) |
83 | ida_free(&misc_minors_ida, DYNAMIC_MINORS - minor - 1); |
84 | else if (minor > MISC_DYNAMIC_MINOR) |
85 | ida_free(&misc_minors_ida, id: minor); |
86 | } |
87 | |
88 | #ifdef CONFIG_PROC_FS |
89 | static void *misc_seq_start(struct seq_file *seq, loff_t *pos) |
90 | { |
91 | mutex_lock(&misc_mtx); |
92 | return seq_list_start(head: &misc_list, pos: *pos); |
93 | } |
94 | |
95 | static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos) |
96 | { |
97 | return seq_list_next(v, head: &misc_list, ppos: pos); |
98 | } |
99 | |
100 | static void misc_seq_stop(struct seq_file *seq, void *v) |
101 | { |
102 | mutex_unlock(lock: &misc_mtx); |
103 | } |
104 | |
105 | static int misc_seq_show(struct seq_file *seq, void *v) |
106 | { |
107 | const struct miscdevice *p = list_entry(v, struct miscdevice, list); |
108 | |
109 | seq_printf(m: seq, fmt: "%3i %s\n" , p->minor, p->name ? p->name : "" ); |
110 | 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 | static int misc_open(struct inode *inode, struct file *file) |
123 | { |
124 | int minor = iminor(inode); |
125 | struct miscdevice *c = NULL, *iter; |
126 | int err = -ENODEV; |
127 | const struct file_operations *new_fops = NULL; |
128 | |
129 | mutex_lock(&misc_mtx); |
130 | |
131 | list_for_each_entry(iter, &misc_list, list) { |
132 | if (iter->minor != minor) |
133 | continue; |
134 | c = iter; |
135 | new_fops = fops_get(iter->fops); |
136 | break; |
137 | } |
138 | |
139 | if (!new_fops) { |
140 | mutex_unlock(lock: &misc_mtx); |
141 | request_module("char-major-%d-%d" , MISC_MAJOR, minor); |
142 | mutex_lock(&misc_mtx); |
143 | |
144 | list_for_each_entry(iter, &misc_list, list) { |
145 | if (iter->minor != minor) |
146 | continue; |
147 | c = iter; |
148 | new_fops = fops_get(iter->fops); |
149 | break; |
150 | } |
151 | 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 | file->private_data = c; |
161 | |
162 | err = 0; |
163 | replace_fops(file, new_fops); |
164 | if (file->f_op->open) |
165 | err = file->f_op->open(inode, file); |
166 | fail: |
167 | mutex_unlock(lock: &misc_mtx); |
168 | return err; |
169 | } |
170 | |
171 | static char *misc_devnode(const struct device *dev, umode_t *mode) |
172 | { |
173 | const struct miscdevice *c = dev_get_drvdata(dev); |
174 | |
175 | if (mode && c->mode) |
176 | *mode = c->mode; |
177 | if (c->nodename) |
178 | return kstrdup(s: c->nodename, GFP_KERNEL); |
179 | return NULL; |
180 | } |
181 | |
182 | static const struct class misc_class = { |
183 | .name = "misc" , |
184 | .devnode = misc_devnode, |
185 | }; |
186 | |
187 | static const struct file_operations misc_fops = { |
188 | .owner = THIS_MODULE, |
189 | .open = misc_open, |
190 | .llseek = noop_llseek, |
191 | }; |
192 | |
193 | /** |
194 | * misc_register - register a miscellaneous device |
195 | * @misc: device structure |
196 | * |
197 | * Register a miscellaneous device with the kernel. If the minor |
198 | * number is set to %MISC_DYNAMIC_MINOR a minor number is assigned |
199 | * and placed in the minor field of the structure. For other cases |
200 | * the minor number requested is used. |
201 | * |
202 | * The structure passed is linked into the kernel and may not be |
203 | * destroyed until it has been unregistered. By default, an open() |
204 | * syscall to the device sets file->private_data to point to the |
205 | * structure. Drivers don't need open in fops for this. |
206 | * |
207 | * A zero is returned on success and a negative errno code for |
208 | * failure. |
209 | */ |
210 | |
211 | int misc_register(struct miscdevice *misc) |
212 | { |
213 | dev_t dev; |
214 | int err = 0; |
215 | bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR); |
216 | |
217 | INIT_LIST_HEAD(list: &misc->list); |
218 | |
219 | mutex_lock(&misc_mtx); |
220 | |
221 | if (is_dynamic) { |
222 | int i = misc_minor_alloc(); |
223 | |
224 | if (i < 0) { |
225 | err = -EBUSY; |
226 | goto out; |
227 | } |
228 | misc->minor = i; |
229 | } else { |
230 | struct miscdevice *c; |
231 | |
232 | list_for_each_entry(c, &misc_list, list) { |
233 | if (c->minor == misc->minor) { |
234 | err = -EBUSY; |
235 | goto out; |
236 | } |
237 | } |
238 | } |
239 | |
240 | dev = MKDEV(MISC_MAJOR, misc->minor); |
241 | |
242 | misc->this_device = |
243 | device_create_with_groups(cls: &misc_class, parent: misc->parent, devt: dev, |
244 | drvdata: misc, groups: misc->groups, fmt: "%s" , misc->name); |
245 | if (IS_ERR(ptr: misc->this_device)) { |
246 | if (is_dynamic) { |
247 | misc_minor_free(minor: misc->minor); |
248 | misc->minor = MISC_DYNAMIC_MINOR; |
249 | } |
250 | err = PTR_ERR(ptr: misc->this_device); |
251 | goto out; |
252 | } |
253 | |
254 | /* |
255 | * Add it to the front, so that later devices can "override" |
256 | * earlier defaults |
257 | */ |
258 | list_add(new: &misc->list, head: &misc_list); |
259 | out: |
260 | mutex_unlock(lock: &misc_mtx); |
261 | return err; |
262 | } |
263 | EXPORT_SYMBOL(misc_register); |
264 | |
265 | /** |
266 | * misc_deregister - unregister a miscellaneous device |
267 | * @misc: device to unregister |
268 | * |
269 | * Unregister a miscellaneous device that was previously |
270 | * successfully registered with misc_register(). |
271 | */ |
272 | |
273 | void misc_deregister(struct miscdevice *misc) |
274 | { |
275 | if (WARN_ON(list_empty(&misc->list))) |
276 | return; |
277 | |
278 | mutex_lock(&misc_mtx); |
279 | list_del(entry: &misc->list); |
280 | device_destroy(cls: &misc_class, MKDEV(MISC_MAJOR, misc->minor)); |
281 | misc_minor_free(minor: misc->minor); |
282 | mutex_unlock(lock: &misc_mtx); |
283 | } |
284 | EXPORT_SYMBOL(misc_deregister); |
285 | |
286 | static int __init misc_init(void) |
287 | { |
288 | int err; |
289 | struct proc_dir_entry *ret; |
290 | |
291 | ret = proc_create_seq("misc" , 0, NULL, &misc_seq_ops); |
292 | err = class_register(class: &misc_class); |
293 | if (err) |
294 | goto fail_remove; |
295 | |
296 | err = -EIO; |
297 | if (register_chrdev(MISC_MAJOR, name: "misc" , fops: &misc_fops)) |
298 | goto fail_printk; |
299 | return 0; |
300 | |
301 | fail_printk: |
302 | pr_err("unable to get major %d for misc devices\n" , MISC_MAJOR); |
303 | class_unregister(class: &misc_class); |
304 | fail_remove: |
305 | if (ret) |
306 | remove_proc_entry("misc" , NULL); |
307 | return err; |
308 | } |
309 | subsys_initcall(misc_init); |
310 | |