1 /*
2 * Telephony registration for Linux
3 *
4 * (c) Copyright 1999 Red Hat Software Inc.
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public License
8 * as published by the Free Software Foundation; either version
9 * 2 of the License, or (at your option) any later version.
10 *
11 * Author: Alan Cox, <alan@lxorguk.ukuu.org.uk>
12 *
13 * Fixes: Mar 01 2000 Thomas Sparr, <thomas.l.sparr@telia.com>
14 * phone_register_device now works with unit!=PHONE_UNIT_ANY
15 */
16
17 #include <linux/module.h>
18 #include <linux/types.h>
19 #include <linux/kernel.h>
20 #include <linux/fs.h>
21 #include <linux/mm.h>
22 #include <linux/string.h>
23 #include <linux/errno.h>
24 #include <linux/phonedev.h>
25 #include <linux/init.h>
26 #include <asm/uaccess.h>
27 #include <asm/system.h>
28
29 #include <linux/kmod.h>
30 #include <linux/sem.h>
31 #include <linux/mutex.h>
32
33 #define PHONE_NUM_DEVICES 256
34
35 /*
36 * Active devices
37 */
38
39 static struct phone_device *phone_device[PHONE_NUM_DEVICES];
40 static DEFINE_MUTEX(phone_lock);
41
42 /*
43 * Open a phone device.
44 */
45
46 static int phone_open(struct inode *inode, struct file *file)
47 {
48 unsigned int minor = iminor(inode);
49 int err = 0;
50 struct phone_device *p;
51 const struct file_operations *old_fops, *new_fops = NULL;
52
53 if (minor >= PHONE_NUM_DEVICES)
54 return -ENODEV;
55
56 mutex_lock(&phone_lock);
57 p = phone_device[minor];
58 if (p)
59 new_fops = fops_get(p->f_op);
60 if (!new_fops) {
61 mutex_unlock(&phone_lock);
62 request_module("char-major-%d-%d", PHONE_MAJOR, minor);
63 mutex_lock(&phone_lock);
64 p = phone_device[minor];
65 if (p == NULL || (new_fops = fops_get(p->f_op)) == NULL)
66 {
67 err=-ENODEV;
68 goto end;
69 }
70 }
71 old_fops = file->f_op;
72 file->f_op = new_fops;
73 if (p->open)
74 err = p->open(p, file); /* Tell the device it is open */
75 if (err) {
76 fops_put(file->f_op);
77 file->f_op = fops_get(old_fops);
78 }
79 fops_put(old_fops);
80 end:
81 mutex_unlock(&phone_lock);
82 return err;
83 }
84
85 /*
86 * Telephony For Linux device drivers request registration here.
87 */
88
89 int phone_register_device(struct phone_device *p, int unit)
90 {
91 int base;
92 int end;
93 int i;
94
95 base = 0;
96 end = PHONE_NUM_DEVICES - 1;
97
98 if (unit != PHONE_UNIT_ANY) {
99 base = unit;
100 end = unit + 1; /* enter the loop at least one time */
101 }
102
103 mutex_lock(&phone_lock);
104 for (i = base; i < end; i++) {
105 if (phone_device[i] == NULL) {
106 phone_device[i] = p;
107 p->minor = i;
108 mutex_unlock(&phone_lock);
109 return 0;
110 }
111 }
112 mutex_unlock(&phone_lock);
113 return -ENFILE;
114 }
115
116 /*
117 * Unregister an unused Telephony for linux device
118 */
119
120 void phone_unregister_device(struct phone_device *pfd)
121 {
122 mutex_lock(&phone_lock);
123 if (likely(phone_device[pfd->minor] == pfd))
124 phone_device[pfd->minor] = NULL;
125 mutex_unlock(&phone_lock);
126 }
127
128
129 static const struct file_operations phone_fops =
130 {
131 .owner = THIS_MODULE,
132 .open = phone_open,
133 };
134
135 /*
136 * Board init functions
137 */
138
139
140 /*
141 * Initialise Telephony for linux
142 */
143
144 static int __init telephony_init(void)
145 {
146 printk(KERN_INFO "Linux telephony interface: v1.00\n");
147 if (register_chrdev(PHONE_MAJOR, "telephony", &phone_fops)) {
148 printk("phonedev: unable to get major %d\n", PHONE_MAJOR);
149 return -EIO;
150 }
151
152 return 0;
153 }
154
155 static void __exit telephony_exit(void)
156 {
157 unregister_chrdev(PHONE_MAJOR, "telephony");
158 }
159
160 module_init(telephony_init);
161 module_exit(telephony_exit);
162
163 MODULE_LICENSE("GPL");
164
165 EXPORT_SYMBOL(phone_register_device);
166 EXPORT_SYMBOL(phone_unregister_device);
167
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