xref: /openbmc/linux/drivers/char/misc.c (revision e868d61272caa648214046a096e5a6bfc068dc8c)
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/slab.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 
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 unsigned char misc_minors[DYNAMIC_MINORS / 8];
64 
65 extern int pmu_device_init(void);
66 
67 #ifdef CONFIG_PROC_FS
68 static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
69 {
70 	struct miscdevice *p;
71 	loff_t off = 0;
72 
73 	mutex_lock(&misc_mtx);
74 	list_for_each_entry(p, &misc_list, list) {
75 		if (*pos == off++)
76 			return p;
77 	}
78 	return NULL;
79 }
80 
81 static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
82 {
83 	struct list_head *n = ((struct miscdevice *)v)->list.next;
84 
85 	++*pos;
86 
87 	return (n != &misc_list) ? list_entry(n, struct miscdevice, list)
88 		 : NULL;
89 }
90 
91 static void misc_seq_stop(struct seq_file *seq, void *v)
92 {
93 	mutex_unlock(&misc_mtx);
94 }
95 
96 static int misc_seq_show(struct seq_file *seq, void *v)
97 {
98 	const struct miscdevice *p = v;
99 
100 	seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
101 	return 0;
102 }
103 
104 
105 static struct seq_operations misc_seq_ops = {
106 	.start = misc_seq_start,
107 	.next  = misc_seq_next,
108 	.stop  = misc_seq_stop,
109 	.show  = misc_seq_show,
110 };
111 
112 static int misc_seq_open(struct inode *inode, struct file *file)
113 {
114 	return seq_open(file, &misc_seq_ops);
115 }
116 
117 static const struct file_operations misc_proc_fops = {
118 	.owner	 = THIS_MODULE,
119 	.open    = misc_seq_open,
120 	.read    = seq_read,
121 	.llseek  = seq_lseek,
122 	.release = seq_release,
123 };
124 #endif
125 
126 static int misc_open(struct inode * inode, struct file * file)
127 {
128 	int minor = iminor(inode);
129 	struct miscdevice *c;
130 	int err = -ENODEV;
131 	const struct file_operations *old_fops, *new_fops = NULL;
132 
133 	mutex_lock(&misc_mtx);
134 
135 	list_for_each_entry(c, &misc_list, list) {
136 		if (c->minor == minor) {
137 			new_fops = fops_get(c->fops);
138 			break;
139 		}
140 	}
141 
142 	if (!new_fops) {
143 		mutex_unlock(&misc_mtx);
144 		request_module("char-major-%d-%d", MISC_MAJOR, minor);
145 		mutex_lock(&misc_mtx);
146 
147 		list_for_each_entry(c, &misc_list, list) {
148 			if (c->minor == minor) {
149 				new_fops = fops_get(c->fops);
150 				break;
151 			}
152 		}
153 		if (!new_fops)
154 			goto fail;
155 	}
156 
157 	err = 0;
158 	old_fops = file->f_op;
159 	file->f_op = new_fops;
160 	if (file->f_op->open) {
161 		err=file->f_op->open(inode,file);
162 		if (err) {
163 			fops_put(file->f_op);
164 			file->f_op = fops_get(old_fops);
165 		}
166 	}
167 	fops_put(old_fops);
168 fail:
169 	mutex_unlock(&misc_mtx);
170 	return err;
171 }
172 
173 static struct class *misc_class;
174 
175 static const struct file_operations misc_fops = {
176 	.owner		= THIS_MODULE,
177 	.open		= misc_open,
178 };
179 
180 
181 /**
182  *	misc_register	-	register a miscellaneous device
183  *	@misc: device structure
184  *
185  *	Register a miscellaneous device with the kernel. If the minor
186  *	number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
187  *	and placed in the minor field of the structure. For other cases
188  *	the minor number requested is used.
189  *
190  *	The structure passed is linked into the kernel and may not be
191  *	destroyed until it has been unregistered.
192  *
193  *	A zero is returned on success and a negative errno code for
194  *	failure.
195  */
196 
197 int misc_register(struct miscdevice * misc)
198 {
199 	struct miscdevice *c;
200 	dev_t dev;
201 	int err = 0;
202 
203 	INIT_LIST_HEAD(&misc->list);
204 
205 	mutex_lock(&misc_mtx);
206 	list_for_each_entry(c, &misc_list, list) {
207 		if (c->minor == misc->minor) {
208 			mutex_unlock(&misc_mtx);
209 			return -EBUSY;
210 		}
211 	}
212 
213 	if (misc->minor == MISC_DYNAMIC_MINOR) {
214 		int i = DYNAMIC_MINORS;
215 		while (--i >= 0)
216 			if ( (misc_minors[i>>3] & (1 << (i&7))) == 0)
217 				break;
218 		if (i<0) {
219 			mutex_unlock(&misc_mtx);
220 			return -EBUSY;
221 		}
222 		misc->minor = i;
223 	}
224 
225 	if (misc->minor < DYNAMIC_MINORS)
226 		misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7);
227 	dev = MKDEV(MISC_MAJOR, misc->minor);
228 
229 	misc->this_device = device_create(misc_class, misc->parent, dev,
230 					  "%s", misc->name);
231 	if (IS_ERR(misc->this_device)) {
232 		err = PTR_ERR(misc->this_device);
233 		goto out;
234 	}
235 
236 	/*
237 	 * Add it to the front, so that later devices can "override"
238 	 * earlier defaults
239 	 */
240 	list_add(&misc->list, &misc_list);
241  out:
242 	mutex_unlock(&misc_mtx);
243 	return err;
244 }
245 
246 /**
247  *	misc_deregister - unregister a miscellaneous device
248  *	@misc: device to unregister
249  *
250  *	Unregister a miscellaneous device that was previously
251  *	successfully registered with misc_register(). Success
252  *	is indicated by a zero return, a negative errno code
253  *	indicates an error.
254  */
255 
256 int misc_deregister(struct miscdevice * misc)
257 {
258 	int i = misc->minor;
259 
260 	if (list_empty(&misc->list))
261 		return -EINVAL;
262 
263 	mutex_lock(&misc_mtx);
264 	list_del(&misc->list);
265 	device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
266 	if (i < DYNAMIC_MINORS && i>0) {
267 		misc_minors[i>>3] &= ~(1 << (misc->minor & 7));
268 	}
269 	mutex_unlock(&misc_mtx);
270 	return 0;
271 }
272 
273 EXPORT_SYMBOL(misc_register);
274 EXPORT_SYMBOL(misc_deregister);
275 
276 static int __init misc_init(void)
277 {
278 #ifdef CONFIG_PROC_FS
279 	struct proc_dir_entry *ent;
280 
281 	ent = create_proc_entry("misc", 0, NULL);
282 	if (ent)
283 		ent->proc_fops = &misc_proc_fops;
284 #endif
285 	misc_class = class_create(THIS_MODULE, "misc");
286 	if (IS_ERR(misc_class))
287 		return PTR_ERR(misc_class);
288 
289 	if (register_chrdev(MISC_MAJOR,"misc",&misc_fops)) {
290 		printk("unable to get major %d for misc devices\n",
291 		       MISC_MAJOR);
292 		class_destroy(misc_class);
293 		return -EIO;
294 	}
295 	return 0;
296 }
297 subsys_initcall(misc_init);
298