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@redhat.com>
  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/version.h>
  18 #include <linux/module.h>
  19 #include <linux/types.h>
  20 #include <linux/kernel.h>
  21 #include <linux/fs.h>
  22 #include <linux/mm.h>
  23 #include <linux/string.h>
  24 #include <linux/errno.h>
  25 #include <linux/phonedev.h>
  26 #include <linux/init.h>
  27 #include <asm/uaccess.h>
  28 #include <asm/system.h>
  29
  30 #include <linux/kmod.h>
  31 #include <linux/sem.h>
  32
  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 DECLARE_MUTEX(phone_lock);
  42
  43 /*
  44  *    Open a phone device.
  45  */
  46
  47 static int phone_open(struct inode *inode, struct file *file)
  48 {
  49         unsigned int minor = minor(inode->i_rdev);
  50         int err = 0;
  51         struct phone_device *p;
  52         struct file_operations *old_fops, *new_fops = NULL;
  53
  54         if (minor >= PHONE_NUM_DEVICES)
  55                 return -ENODEV;
  56
  57         down(&phone_lock);
  58         p = phone_device[minor];
  59         if (p)
  60                 new_fops = fops_get(p->f_op);
  61         if (!new_fops) {
  62                 up(&phone_lock);
  63                 request_module("char-major-%d-%d", PHONE_MAJOR, minor);
  64                 down(&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         up(&phone_lock);
  83         return err;
  84 }
  85
  86 /*
  87  *    Telephony For Linux device drivers request registration here.
  88  */
  89
  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         down(&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                         up(&phone_lock);
 110                         return 0;
 111                 }
 112         }
 113         up(&phone_lock);
 114         return -ENFILE;
 115 }
 116
 117 /*
 118  *    Unregister an unused Telephony for linux device
 119  */
 120
 121 void phone_unregister_device(struct phone_device *pfd)
 122 {
 123         down(&phone_lock);
 124         if (phone_device[pfd->minor] != pfd)
 125                 panic("phone: bad unregister");
 126         phone_device[pfd->minor] = NULL;
 127         up(&phone_lock);
 128 }
 129
 130
 131 static struct file_operations phone_fops =
 132 {
 133         .owner          = THIS_MODULE,
 134         .open           = phone_open,
 135 };
 136
 137 /*
 138  *      Board init functions
 139  */
 140
 141
 142 /*
 143  *    Initialise Telephony for linux
 144  */
 145
 146 static int __init telephony_init(void)
 147 {
 148         printk(KERN_INFO "Linux telephony interface: v1.00\n");
 149         if (register_chrdev(PHONE_MAJOR, "telephony", &phone_fops)) {
 150                 printk("phonedev: unable to get major %d\n", PHONE_MAJOR);
 151                 return -EIO;
 152         }
 153
 154         return 0;
 155 }
 156
 157 static void __exit telephony_exit(void)
 158 {
 159         unregister_chrdev(PHONE_MAJOR, "telephony");
 160 }
 161
 162 module_init(telephony_init);
 163 module_exit(telephony_exit);
 164
 165 MODULE_LICENSE("GPL");
 166
 167 EXPORT_SYMBOL(phone_register_device);
 168 EXPORT_SYMBOL(phone_unregister_device);