Root/drivers/char/misc.c

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 */
56static LIST_HEAD(misc_list);
57static DEFINE_MUTEX(misc_mtx);
58
59/*
60 * Assigned numbers, used for dynamic minors
61 */
62#define DYNAMIC_MINORS 64 /* like dynamic majors */
63static DECLARE_BITMAP(misc_minors, DYNAMIC_MINORS);
64
65#ifdef CONFIG_PROC_FS
66static 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
72static 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
77static void misc_seq_stop(struct seq_file *seq, void *v)
78{
79    mutex_unlock(&misc_mtx);
80}
81
82static 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
91static 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
98static int misc_seq_open(struct inode *inode, struct file *file)
99{
100    return seq_open(file, &misc_seq_ops);
101}
102
103static 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
112static 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);
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
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 
184int 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
242int 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
258EXPORT_SYMBOL(misc_register);
259EXPORT_SYMBOL(misc_deregister);
260
261static 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
272static 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
290fail_printk:
291    printk("unable to get major %d for misc devices\n", MISC_MAJOR);
292    class_destroy(misc_class);
293fail_remove:
294    remove_proc_entry("misc", NULL);
295    return err;
296}
297subsys_initcall(misc_init);
298

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