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 */
56 static LIST_HEAD(misc_list);
57 static DEFINE_MUTEX(misc_mtx);
58
59 /*
60 * Assigned numbers, used for dynamic minors
61 */
62 #define DYNAMIC_MINORS 64 /* like dynamic majors */
63 static DECLARE_BITMAP(misc_minors, DYNAMIC_MINORS);
64
65 #ifdef CONFIG_PROC_FS
misc_seq_start(struct seq_file * seq,loff_t * pos)66 static 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
misc_seq_next(struct seq_file * seq,void * v,loff_t * pos)72 static 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
misc_seq_stop(struct seq_file * seq,void * v)77 static void misc_seq_stop(struct seq_file *seq, void *v)
78 {
79 mutex_unlock(&misc_mtx);
80 }
81
misc_seq_show(struct seq_file * seq,void * v)82 static 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
91 static 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
misc_seq_open(struct inode * inode,struct file * file)98 static int misc_seq_open(struct inode *inode, struct file *file)
99 {
100 return seq_open(file, &misc_seq_ops);
101 }
102
103 static 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
misc_open(struct inode * inode,struct file * file)112 static 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 *old_fops, *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 err = 0;
144 old_fops = file->f_op;
145 file->f_op = new_fops;
146 if (file->f_op->open) {
147 file->private_data = c;
148 err=file->f_op->open(inode,file);
149 if (err) {
150 fops_put(file->f_op);
151 file->f_op = fops_get(old_fops);
152 }
153 }
154 fops_put(old_fops);
155 fail:
156 mutex_unlock(&misc_mtx);
157 return err;
158 }
159
160 static struct class *misc_class;
161
162 static const struct file_operations misc_fops = {
163 .owner = THIS_MODULE,
164 .open = misc_open,
165 .llseek = noop_llseek,
166 };
167
168 /**
169 * misc_register - register a miscellaneous device
170 * @misc: device structure
171 *
172 * Register a miscellaneous device with the kernel. If the minor
173 * number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
174 * and placed in the minor field of the structure. For other cases
175 * the minor number requested is used.
176 *
177 * The structure passed is linked into the kernel and may not be
178 * destroyed until it has been unregistered.
179 *
180 * A zero is returned on success and a negative errno code for
181 * failure.
182 */
183
misc_register(struct miscdevice * misc)184 int misc_register(struct miscdevice * misc)
185 {
186 struct miscdevice *c;
187 dev_t dev;
188 int err = 0;
189
190 INIT_LIST_HEAD(&misc->list);
191
192 mutex_lock(&misc_mtx);
193 list_for_each_entry(c, &misc_list, list) {
194 if (c->minor == misc->minor) {
195 mutex_unlock(&misc_mtx);
196 return -EBUSY;
197 }
198 }
199
200 if (misc->minor == MISC_DYNAMIC_MINOR) {
201 int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS);
202 if (i >= DYNAMIC_MINORS) {
203 mutex_unlock(&misc_mtx);
204 return -EBUSY;
205 }
206 misc->minor = DYNAMIC_MINORS - i - 1;
207 set_bit(i, misc_minors);
208 }
209
210 dev = MKDEV(MISC_MAJOR, misc->minor);
211
212 misc->this_device = device_create(misc_class, misc->parent, dev,
213 misc, "%s", misc->name);
214 if (IS_ERR(misc->this_device)) {
215 int i = DYNAMIC_MINORS - misc->minor - 1;
216 if (i < DYNAMIC_MINORS && i >= 0)
217 clear_bit(i, misc_minors);
218 err = PTR_ERR(misc->this_device);
219 goto out;
220 }
221
222 /*
223 * Add it to the front, so that later devices can "override"
224 * earlier defaults
225 */
226 list_add(&misc->list, &misc_list);
227 out:
228 mutex_unlock(&misc_mtx);
229 return err;
230 }
231
232 /**
233 * misc_deregister - unregister a miscellaneous device
234 * @misc: device to unregister
235 *
236 * Unregister a miscellaneous device that was previously
237 * successfully registered with misc_register(). Success
238 * is indicated by a zero return, a negative errno code
239 * indicates an error.
240 */
241
misc_deregister(struct miscdevice * misc)242 int misc_deregister(struct miscdevice *misc)
243 {
244 int i = DYNAMIC_MINORS - misc->minor - 1;
245
246 if (WARN_ON(list_empty(&misc->list)))
247 return -EINVAL;
248
249 mutex_lock(&misc_mtx);
250 list_del(&misc->list);
251 device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
252 if (i < DYNAMIC_MINORS && i >= 0)
253 clear_bit(i, misc_minors);
254 mutex_unlock(&misc_mtx);
255 return 0;
256 }
257
258 EXPORT_SYMBOL(misc_register);
259 EXPORT_SYMBOL(misc_deregister);
260
misc_devnode(struct device * dev,umode_t * mode)261 static char *misc_devnode(struct device *dev, umode_t *mode)
262 {
263 struct miscdevice *c = dev_get_drvdata(dev);
264
265 if (mode && c->mode)
266 *mode = c->mode;
267 if (c->nodename)
268 return kstrdup(c->nodename, GFP_KERNEL);
269 return NULL;
270 }
271
misc_init(void)272 static int __init misc_init(void)
273 {
274 int err;
275
276 #ifdef CONFIG_PROC_FS
277 proc_create("misc", 0, NULL, &misc_proc_fops);
278 #endif
279 misc_class = class_create(THIS_MODULE, "misc");
280 err = PTR_ERR(misc_class);
281 if (IS_ERR(misc_class))
282 goto fail_remove;
283
284 err = -EIO;
285 if (register_chrdev(MISC_MAJOR,"misc",&misc_fops))
286 goto fail_printk;
287 misc_class->devnode = misc_devnode;
288 return 0;
289
290 fail_printk:
291 printk("unable to get major %d for misc devices\n", MISC_MAJOR);
292 class_destroy(misc_class);
293 fail_remove:
294 remove_proc_entry("misc", NULL);
295 return err;
296 }
297 subsys_initcall(misc_init);
298