2 * linux/drivers/char/misc.c
4 * Generic misc open routine by Johan Myreen
6 * Based on code from Linus
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.
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.
16 * Support for loadable modules. 8-Sep-95 Philip Blundell <pjb27@cam.ac.uk>
18 * Fixed a failing symbol register to free the device registration
19 * Alan Cox <alan@lxorguk.ukuu.org.uk> 21-Jan-96
21 * Dynamic minors and /proc/mice by Alessandro Rubini. 26-Mar-96
23 * Renamed to misc and miscdevice to be more accurate. Alan Cox 26-Mar-96
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>
30 * Changes for kmod (from kerneld):
31 * Cyrus Durgin <cider@speakeasy.org>
33 * Added devfs support. Richard Gooch <rgooch@atnf.csiro.au> 10-Jan-1998
36 #include <linux/module.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>
54 * Head entry for the doubly linked miscdevice list
56 static LIST_HEAD(misc_list);
57 static DEFINE_MUTEX(misc_mtx);
60 * Assigned numbers, used for dynamic minors
62 #define DYNAMIC_MINORS 64 /* like dynamic majors */
63 static unsigned char misc_minors[DYNAMIC_MINORS / 8];
65 extern int pmu_device_init(void);
68 static void *misc_seq_start(struct seq_file *seq, loff_t *pos)
70 mutex_lock(&misc_mtx);
71 return seq_list_start(&misc_list, *pos);
74 static void *misc_seq_next(struct seq_file *seq, void *v, loff_t *pos)
76 return seq_list_next(v, &misc_list, pos);
79 static void misc_seq_stop(struct seq_file *seq, void *v)
81 mutex_unlock(&misc_mtx);
84 static int misc_seq_show(struct seq_file *seq, void *v)
86 const struct miscdevice *p = list_entry(v, struct miscdevice, list);
88 seq_printf(seq, "%3i %s\n", p->minor, p->name ? p->name : "");
93 static struct seq_operations misc_seq_ops = {
94 .start = misc_seq_start,
95 .next = misc_seq_next,
96 .stop = misc_seq_stop,
97 .show = misc_seq_show,
100 static int misc_seq_open(struct inode *inode, struct file *file)
102 return seq_open(file, &misc_seq_ops);
105 static const struct file_operations misc_proc_fops = {
106 .owner = THIS_MODULE,
107 .open = misc_seq_open,
110 .release = seq_release,
114 static int misc_open(struct inode * inode, struct file * file)
116 int minor = iminor(inode);
117 struct miscdevice *c;
119 const struct file_operations *old_fops, *new_fops = NULL;
121 mutex_lock(&misc_mtx);
123 list_for_each_entry(c, &misc_list, list) {
124 if (c->minor == minor) {
125 new_fops = fops_get(c->fops);
131 mutex_unlock(&misc_mtx);
132 request_module("char-major-%d-%d", MISC_MAJOR, minor);
133 mutex_lock(&misc_mtx);
135 list_for_each_entry(c, &misc_list, list) {
136 if (c->minor == minor) {
137 new_fops = fops_get(c->fops);
146 old_fops = file->f_op;
147 file->f_op = new_fops;
148 if (file->f_op->open) {
149 err=file->f_op->open(inode,file);
151 fops_put(file->f_op);
152 file->f_op = fops_get(old_fops);
157 mutex_unlock(&misc_mtx);
161 static struct class *misc_class;
163 static const struct file_operations misc_fops = {
164 .owner = THIS_MODULE,
170 * misc_register - register a miscellaneous device
171 * @misc: device structure
173 * Register a miscellaneous device with the kernel. If the minor
174 * number is set to %MISC_DYNAMIC_MINOR a minor number is assigned
175 * and placed in the minor field of the structure. For other cases
176 * the minor number requested is used.
178 * The structure passed is linked into the kernel and may not be
179 * destroyed until it has been unregistered.
181 * A zero is returned on success and a negative errno code for
185 int misc_register(struct miscdevice * misc)
187 struct miscdevice *c;
191 INIT_LIST_HEAD(&misc->list);
193 mutex_lock(&misc_mtx);
194 list_for_each_entry(c, &misc_list, list) {
195 if (c->minor == misc->minor) {
196 mutex_unlock(&misc_mtx);
201 if (misc->minor == MISC_DYNAMIC_MINOR) {
202 int i = DYNAMIC_MINORS;
204 if ( (misc_minors[i>>3] & (1 << (i&7))) == 0)
207 mutex_unlock(&misc_mtx);
213 if (misc->minor < DYNAMIC_MINORS)
214 misc_minors[misc->minor >> 3] |= 1 << (misc->minor & 7);
215 dev = MKDEV(MISC_MAJOR, misc->minor);
217 misc->this_device = device_create(misc_class, misc->parent, dev,
219 if (IS_ERR(misc->this_device)) {
220 err = PTR_ERR(misc->this_device);
225 * Add it to the front, so that later devices can "override"
228 list_add(&misc->list, &misc_list);
230 mutex_unlock(&misc_mtx);
235 * misc_deregister - unregister a miscellaneous device
236 * @misc: device to unregister
238 * Unregister a miscellaneous device that was previously
239 * successfully registered with misc_register(). Success
240 * is indicated by a zero return, a negative errno code
241 * indicates an error.
244 int misc_deregister(struct miscdevice *misc)
248 if (list_empty(&misc->list))
251 mutex_lock(&misc_mtx);
252 list_del(&misc->list);
253 device_destroy(misc_class, MKDEV(MISC_MAJOR, misc->minor));
254 if (i < DYNAMIC_MINORS && i>0) {
255 misc_minors[i>>3] &= ~(1 << (misc->minor & 7));
257 mutex_unlock(&misc_mtx);
261 EXPORT_SYMBOL(misc_register);
262 EXPORT_SYMBOL(misc_deregister);
264 static int __init misc_init(void)
268 #ifdef CONFIG_PROC_FS
269 proc_create("misc", 0, NULL, &misc_proc_fops);
271 misc_class = class_create(THIS_MODULE, "misc");
272 err = PTR_ERR(misc_class);
273 if (IS_ERR(misc_class))
277 if (register_chrdev(MISC_MAJOR,"misc",&misc_fops))
282 printk("unable to get major %d for misc devices\n", MISC_MAJOR);
283 class_destroy(misc_class);
285 remove_proc_entry("misc", NULL);
288 subsys_initcall(misc_init);