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