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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
56
57static LIST_HEAD(misc_list);
58static DEFINE_MUTEX(misc_mtx);
59
60
61
62
63#define DYNAMIC_MINORS 64
64static DECLARE_BITMAP(misc_minors, DYNAMIC_MINORS);
65
66#ifdef CONFIG_PROC_FS
67static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
68{
69 mutex_lock(&misc_mtx);
70 return seq_list_start(&misc_list, *pos);
71}
72
73static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
74{
75 return seq_list_next(v, &misc_list, pos);
76}
77
78static void misc_seq_stop(struct seq_file *seq, void *v)
79{
80 mutex_unlock(&misc_mtx);
81}
82
83static int misc_seq_show(struct seq_file *seq, void *v)
84{
85 const struct miscdevice *p = list_entry(v, struct miscdevice, list);
86
87 seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
88 return 0;
89}
90
91
92static const struct seq_operations misc_seq_ops = {
93 .start = misc_seq_start,
94 .next = misc_seq_next,
95 .stop = misc_seq_stop,
96 .show = misc_seq_show,
97};
98
99static int misc_seq_open(struct inode *inode, struct file *file)
100{
101 return seq_open(file, &misc_seq_ops);
102}
103
104static const struct file_operations misc_proc_fops = {
105 .owner = THIS_MODULE,
106 .open = misc_seq_open,
107 .read = seq_read,
108 .llseek = seq_lseek,
109 .release = seq_release,
110};
111#endif
112
113static int misc_open(struct inode *inode, struct file *file)
114{
115 int minor = iminor(inode);
116 struct miscdevice *c;
117 int err = -ENODEV;
118 const struct file_operations *new_fops = NULL;
119
120 mutex_lock(&misc_mtx);
121
122 list_for_each_entry(c, &misc_list, list) {
123 if (c->minor == minor) {
124 new_fops = fops_get(c->fops);
125 break;
126 }
127 }
128
129 if (!new_fops) {
130 mutex_unlock(&misc_mtx);
131 request_module("char-major-%d-%d", MISC_MAJOR, minor);
132 mutex_lock(&misc_mtx);
133
134 list_for_each_entry(c, &misc_list, list) {
135 if (c->minor == minor) {
136 new_fops = fops_get(c->fops);
137 break;
138 }
139 }
140 if (!new_fops)
141 goto fail;
142 }
143
144
145
146
147
148
149 file->private_data = c;
150
151 err = 0;
152 replace_fops(file, new_fops);
153 if (file->f_op->open)
154 err = file->f_op->open(inode, file);
155fail:
156 mutex_unlock(&misc_mtx);
157 return err;
158}
159
160static struct class *misc_class;
161
162static const struct file_operations misc_fops = {
163 .owner = THIS_MODULE,
164 .open = misc_open,
165 .llseek = noop_llseek,
166};
167
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185
186int misc_register(struct miscdevice *misc)
187{
188 dev_t dev;
189 int err = 0;
190 bool is_dynamic = (misc->minor == MISC_DYNAMIC_MINOR);
191
192 INIT_LIST_HEAD(&misc->list);
193
194 mutex_lock(&misc_mtx);
195
196 if (is_dynamic) {
197 int i = find_first_zero_bit(misc_minors, DYNAMIC_MINORS);
198
199 if (i >= DYNAMIC_MINORS) {
200 err = -EBUSY;
201 goto out;
202 }
203 misc->minor = DYNAMIC_MINORS - i - 1;
204 set_bit(i, misc_minors);
205 } else {
206 struct miscdevice *c;
207
208 list_for_each_entry(c, &misc_list, list) {
209 if (c->minor == misc->minor) {
210 err = -EBUSY;
211 goto out;
212 }
213 }
214 }
215
216 dev = MKDEV(MISC_MAJOR, misc->minor);
217
218 misc->this_device =
219 device_create_with_groups(misc_class, misc->parent, dev,
220 misc, misc->groups, "%s", misc->name);
221 if (IS_ERR(misc->this_device)) {
222 if (is_dynamic) {
223 int i = DYNAMIC_MINORS - misc->minor - 1;
224
225 if (i < DYNAMIC_MINORS && i >= 0)
226 clear_bit(i, misc_minors);
227 misc->minor = MISC_DYNAMIC_MINOR;
228 }
229 err = PTR_ERR(misc->this_device);
230 goto out;
231 }
232
233
234
235
236
237 list_add(&misc->list, &misc_list);
238 out:
239 mutex_unlock(&misc_mtx);
240 return err;
241}
242
243
244
245
246
247
248
249
250
251void misc_deregister(struct miscdevice *misc)
252{
253 int i = DYNAMIC_MINORS - misc->minor - 1;
254
255 if (WARN_ON(list_empty(&misc->list)))
256 return;
257
258 mutex_lock(&misc_mtx);
259 list_del(&misc->list);
260 device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
261 if (i < DYNAMIC_MINORS && i >= 0)
262 clear_bit(i, misc_minors);
263 mutex_unlock(&misc_mtx);
264}
265
266EXPORT_SYMBOL(misc_register);
267EXPORT_SYMBOL(misc_deregister);
268
269static char *misc_devnode(struct device *dev, umode_t *mode)
270{
271 struct miscdevice *c = dev_get_drvdata(dev);
272
273 if (mode && c->mode)
274 *mode = c->mode;
275 if (c->nodename)
276 return kstrdup(c->nodename, GFP_KERNEL);
277 return NULL;
278}
279
280static int __init misc_init(void)
281{
282 int err;
283 struct proc_dir_entry *ret;
284
285 ret = proc_create("misc", 0, NULL, &misc_proc_fops);
286 misc_class = class_create(THIS_MODULE, "misc");
287 err = PTR_ERR(misc_class);
288 if (IS_ERR(misc_class))
289 goto fail_remove;
290
291 err = -EIO;
292 if (register_chrdev(MISC_MAJOR, "misc", &misc_fops))
293 goto fail_printk;
294 misc_class->devnode = misc_devnode;
295 return 0;
296
297fail_printk:
298 pr_err("unable to get major %d for misc devices\n", MISC_MAJOR);
299 class_destroy(misc_class);
300fail_remove:
301 if (ret)
302 remove_proc_entry("misc", NULL);
303 return err;
304}
305subsys_initcall(misc_init);
306