/*
   *            Telephony registration for Linux
   *
   *              (c) Copyright 1999 Red Hat Software Inc.
   *
   *              This program is free software; you can redistribute it and/or
   *              modify it under the terms of the GNU General Public License
   *              as published by the Free Software Foundation; either version
   *              2 of the License, or (at your option) any later version.
   *

   * Author:      Alan Cox, <alan@lxorguk.ukuu.org.uk>

   *
   * Fixes:       Mar 01 2000 Thomas Sparr, <thomas.l.sparr@telia.com>
   *              phone_register_device now works with unit!=PHONE_UNIT_ANY
   */
  
  #include <linux/module.h>
  #include <linux/types.h>
  #include <linux/kernel.h>
  #include <linux/fs.h>
  #include <linux/mm.h>
  #include <linux/string.h>
  #include <linux/errno.h>
  #include <linux/phonedev.h>
  #include <linux/init.h>
  #include <asm/uaccess.h>
  #include <asm/system.h>
  
  #include <linux/kmod.h>
  #include <linux/sem.h>

  #include <linux/mutex.h>

  
  #define PHONE_NUM_DEVICES	256
  
  /*
   *    Active devices 
   */
  
  static struct phone_device *phone_device[PHONE_NUM_DEVICES];

  static DEFINE_MUTEX(phone_lock);

  
  /*
   *    Open a phone device.
   */
  
  static int phone_open(struct inode *inode, struct file *file)
  {
  	unsigned int minor = iminor(inode);
  	int err = 0;
  	struct phone_device *p;

  	const struct file_operations *old_fops, *new_fops = NULL;

  
  	if (minor >= PHONE_NUM_DEVICES)
  		return -ENODEV;

  	mutex_lock(&phone_lock);

  	p = phone_device[minor];
  	if (p)
  		new_fops = fops_get(p->f_op);
  	if (!new_fops) {

  		mutex_unlock(&phone_lock);

  		request_module("char-major-%d-%d", PHONE_MAJOR, minor);

  		mutex_lock(&phone_lock);

  		p = phone_device[minor];
  		if (p == NULL || (new_fops = fops_get(p->f_op)) == NULL)
  		{
  			err=-ENODEV;
  			goto end;
  		}
  	}
  	old_fops = file->f_op;
  	file->f_op = new_fops;
  	if (p->open)
  		err = p->open(p, file);	/* Tell the device it is open */
  	if (err) {
  		fops_put(file->f_op);
  		file->f_op = fops_get(old_fops);
  	}
  	fops_put(old_fops);
  end:

  	mutex_unlock(&phone_lock);

  	return err;
  }
  
  /*
   *    Telephony For Linux device drivers request registration here.
   */
  
  int phone_register_device(struct phone_device *p, int unit)
  {
  	int base;
  	int end;
  	int i;
  
  	base = 0;
  	end = PHONE_NUM_DEVICES - 1;
  
  	if (unit != PHONE_UNIT_ANY) {
  		base = unit;
  		end = unit + 1;  /* enter the loop at least one time */
  	}
  	

  	mutex_lock(&phone_lock);

  	for (i = base; i < end; i++) {
  		if (phone_device[i] == NULL) {
  			phone_device[i] = p;
  			p->minor = i;

  			mutex_unlock(&phone_lock);

  			return 0;
  		}
  	}

  	mutex_unlock(&phone_lock);

  	return -ENFILE;
  }
  
  /*
   *    Unregister an unused Telephony for linux device
   */
  
  void phone_unregister_device(struct phone_device *pfd)
  {

  	mutex_lock(&phone_lock);

  	if (likely(phone_device[pfd->minor] == pfd))
  		phone_device[pfd->minor] = NULL;

  	mutex_unlock(&phone_lock);

  }

  static const struct file_operations phone_fops =

  {
  	.owner		= THIS_MODULE,
  	.open		= phone_open,

  	.llseek		= noop_llseek,

  };
  
  /*
   *	Board init functions
   */
   
  
  /*
   *    Initialise Telephony for linux
   */
  
  static int __init telephony_init(void)
  {
  	printk(KERN_INFO "Linux telephony interface: v1.00
  ");
  	if (register_chrdev(PHONE_MAJOR, "telephony", &phone_fops)) {
  		printk("phonedev: unable to get major %d
  ", PHONE_MAJOR);
  		return -EIO;
  	}
  
  	return 0;
  }
  
  static void __exit telephony_exit(void)
  {
  	unregister_chrdev(PHONE_MAJOR, "telephony");
  }
  
  module_init(telephony_init);
  module_exit(telephony_exit);
  
  MODULE_LICENSE("GPL");
  
  EXPORT_SYMBOL(phone_register_device);
  EXPORT_SYMBOL(phone_unregister_device);