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/sched.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                 char modname[32];
  63
  64                 up(&phone_lock);
  65                 sprintf(modname, "char-major-%d-%d", PHONE_MAJOR, minor);
  66                 request_module(modname);
  67                 down(&phone_lock);
  68                 p = phone_device[minor];
  69                 if (p == NULL || (new_fops = fops_get(p->f_op)) == NULL)
  70                 {
  71                         err=-ENODEV;
  72                         goto end;
  73                 }
  74         }
  75         old_fops = file->f_op;
  76         file->f_op = new_fops;
  77         if (p->open)
  78                 err = p->open(p, file); /* Tell the device it is open */
  79         if (err) {
  80                 fops_put(file->f_op);
  81                 file->f_op = fops_get(old_fops);
  82         }
  83         fops_put(old_fops);
  84 end:
  85         up(&phone_lock);
  86         return err;
  87 }
  88
  89 /*
  90  *    Telephony For Linux device drivers request registration here.
  91  */
  92
  93 int phone_register_device(struct phone_device *p, int unit)
  94 {
  95         int base;
  96         int end;
  97         int i;
  98
  99         base = 0;
 100         end = PHONE_NUM_DEVICES - 1;
 101
 102         if (unit != PHONE_UNIT_ANY) {
 103                 base = unit;
 104                 end = unit + 1;  /* enter the loop at least one time */
 105         }
 106
 107         down(&phone_lock);
 108         for (i = base; i < end; i++) {
 109                 if (phone_device[i] == NULL) {
 110                         phone_device[i] = p;
 111                         p->minor = i;
 112                         MOD_INC_USE_COUNT;
 113                         up(&phone_lock);
 114                         return 0;
 115                 }
 116         }
 117         up(&phone_lock);
 118         return -ENFILE;
 119 }
 120
 121 /*
 122  *    Unregister an unused Telephony for linux device
 123  */
 124
 125 void phone_unregister_device(struct phone_device *pfd)
 126 {
 127         down(&phone_lock);
 128         if (phone_device[pfd->minor] != pfd)
 129                 panic("phone: bad unregister");
 130         phone_device[pfd->minor] = NULL;
 131         up(&phone_lock);
 132         MOD_DEC_USE_COUNT;
 133 }
 134
 135
 136 static struct file_operations phone_fops =
 137 {
 138         owner:          THIS_MODULE,
 139         open:           phone_open,
 140 };
 141
 142 /*
 143  *      Board init functions
 144  */
 145
 146
 147 /*
 148  *    Initialise Telephony for linux
 149  */
 150
 151 static int __init telephony_init(void)
 152 {
 153         printk(KERN_INFO "Linux telephony interface: v1.00\n");
 154         if (register_chrdev(PHONE_MAJOR, "telephony", &phone_fops)) {
 155                 printk("phonedev: unable to get major %d\n", PHONE_MAJOR);
 156                 return -EIO;
 157         }
 158
 159         return 0;
 160 }
 161
 162 static void __exit telephony_exit(void)
 163 {
 164         unregister_chrdev(PHONE_MAJOR, "telephony");
 165 }
 166
 167 module_init(telephony_init);
 168 module_exit(telephony_exit);
 169
 170 MODULE_LICENSE("GPL");
 171
 172 EXPORT_SYMBOL(phone_register_device);
 173 EXPORT_SYMBOL(phone_unregister_device);