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 <linux/smp_lock.h>
27 #include <asm/uaccess.h>
28 #include <asm/system.h>
29
30 #include <linux/kmod.h>
31 #include <linux/sem.h>
32 #include <linux/mutex.h>
33
34 #define PHONE_NUM_DEVICES 256
35
36 /*
37 * Active devices
38 */
39
40 static struct phone_device *phone_device[PHONE_NUM_DEVICES];
41 static DEFINE_MUTEX(phone_lock);
42
43 /*
44 * Open a phone device.
45 */
46
phone_open(struct inode * inode,struct file * file)47 static int phone_open(struct inode *inode, struct file *file)
48 {
49 unsigned int minor = iminor(inode);
50 int err = 0;
51 struct phone_device *p;
52 const struct file_operations *old_fops, *new_fops = NULL;
53
54 if (minor >= PHONE_NUM_DEVICES)
55 return -ENODEV;
56
57 mutex_lock(&phone_lock);
58 p = phone_device[minor];
59 if (p)
60 new_fops = fops_get(p->f_op);
61 if (!new_fops) {
62 mutex_unlock(&phone_lock);
63 request_module("char-major-%d-%d", PHONE_MAJOR, minor);
64 mutex_lock(&phone_lock);
65 p = phone_device[minor];
66 if (p == NULL || (new_fops = fops_get(p->f_op)) == NULL)
67 {
68 err=-ENODEV;
69 goto end;
70 }
71 }
72 old_fops = file->f_op;
73 file->f_op = new_fops;
74 if (p->open)
75 err = p->open(p, file); /* Tell the device it is open */
76 if (err) {
77 fops_put(file->f_op);
78 file->f_op = fops_get(old_fops);
79 }
80 fops_put(old_fops);
81 end:
82 mutex_unlock(&phone_lock);
83 return err;
84 }
85
86 /*
87 * Telephony For Linux device drivers request registration here.
88 */
89
phone_register_device(struct phone_device * p,int unit)90 int phone_register_device(struct phone_device *p, int unit)
91 {
92 int base;
93 int end;
94 int i;
95
96 base = 0;
97 end = PHONE_NUM_DEVICES - 1;
98
99 if (unit != PHONE_UNIT_ANY) {
100 base = unit;
101 end = unit + 1; /* enter the loop at least one time */
102 }
103
104 mutex_lock(&phone_lock);
105 for (i = base; i < end; i++) {
106 if (phone_device[i] == NULL) {
107 phone_device[i] = p;
108 p->minor = i;
109 mutex_unlock(&phone_lock);
110 return 0;
111 }
112 }
113 mutex_unlock(&phone_lock);
114 return -ENFILE;
115 }
116
117 /*
118 * Unregister an unused Telephony for linux device
119 */
120
phone_unregister_device(struct phone_device * pfd)121 void phone_unregister_device(struct phone_device *pfd)
122 {
123 mutex_lock(&phone_lock);
124 if (likely(phone_device[pfd->minor] == pfd))
125 phone_device[pfd->minor] = NULL;
126 mutex_unlock(&phone_lock);
127 }
128
129
130 static const struct file_operations phone_fops =
131 {
132 .owner = THIS_MODULE,
133 .open = phone_open,
134 };
135
136 /*
137 * Board init functions
138 */
139
140
141 /*
142 * Initialise Telephony for linux
143 */
144
telephony_init(void)145 static int __init telephony_init(void)
146 {
147 printk(KERN_INFO "Linux telephony interface: v1.00\n");
148 if (register_chrdev(PHONE_MAJOR, "telephony", &phone_fops)) {
149 printk("phonedev: unable to get major %d\n", PHONE_MAJOR);
150 return -EIO;
151 }
152
153 return 0;
154 }
155
telephony_exit(void)156 static void __exit telephony_exit(void)
157 {
158 unregister_chrdev(PHONE_MAJOR, "telephony");
159 }
160
161 module_init(telephony_init);
162 module_exit(telephony_exit);
163
164 MODULE_LICENSE("GPL");
165
166 EXPORT_SYMBOL(phone_register_device);
167 EXPORT_SYMBOL(phone_unregister_device);
168