drivers/telephony/phonedev.c

   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         .llseek         = noop_llseek,
 134 };
 135
 136 /*
 137  *      Board init functions
 138  */
 139
 140
 141 /*
 142  *    Initialise Telephony for linux
 143  */
 144
 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
 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);