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/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 <linux/smp_lock.h>
  27 #include <asm/uaccess.h>
  28 #include <asm/system.h>
  29
  30 #include <linux/kmod.h>
  31 #include <linux/sem.h>
  32 #include <linux/mutex.h>
  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 DEFINE_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 = iminor(inode);
  50         int err = 0;
  51         struct phone_device *p;
  52         const struct file_operations *old_fops, *new_fops = NULL;
  53
  54         if (minor >= PHONE_NUM_DEVICES)
  55                 return -ENODEV;
  56
  57         lock_kernel();
  58         mutex_lock(&phone_lock);
  59         p = phone_device[minor];
  60         if (p)
  61                 new_fops = fops_get(p->f_op);
  62         if (!new_fops) {
  63                 mutex_unlock(&phone_lock);
  64                 request_module("char-major-%d-%d", PHONE_MAJOR, minor);
  65                 mutex_lock(&phone_lock);
  66                 p = phone_device[minor];
  67                 if (p == NULL || (new_fops = fops_get(p->f_op)) == NULL)
  68                 {
  69                         err=-ENODEV;
  70                         goto end;
  71                 }
  72         }
  73         old_fops = file->f_op;
  74         file->f_op = new_fops;
  75         if (p->open)
  76                 err = p->open(p, file); /* Tell the device it is open */
  77         if (err) {
  78                 fops_put(file->f_op);
  79                 file->f_op = fops_get(old_fops);
  80         }
  81         fops_put(old_fops);
  82 end:
  83         mutex_unlock(&phone_lock);
  84         unlock_kernel();
  85         return err;
  86 }
  87
  88 /*
  89  *    Telephony For Linux device drivers request registration here.
  90  */
  91
  92 int phone_register_device(struct phone_device *p, int unit)
  93 {
  94         int base;
  95         int end;
  96         int i;
  97
  98         base = 0;
  99         end = PHONE_NUM_DEVICES - 1;
 100
 101         if (unit != PHONE_UNIT_ANY) {
 102                 base = unit;
 103                 end = unit + 1;  /* enter the loop at least one time */
 104         }
 105
 106         mutex_lock(&phone_lock);
 107         for (i = base; i < end; i++) {
 108                 if (phone_device[i] == NULL) {
 109                         phone_device[i] = p;
 110                         p->minor = i;
 111                         mutex_unlock(&phone_lock);
 112                         return 0;
 113                 }
 114         }
 115         mutex_unlock(&phone_lock);
 116         return -ENFILE;
 117 }
 118
 119 /*
 120  *    Unregister an unused Telephony for linux device
 121  */
 122
 123 void phone_unregister_device(struct phone_device *pfd)
 124 {
 125         mutex_lock(&phone_lock);
 126         if (likely(phone_device[pfd->minor] == pfd))
 127                 phone_device[pfd->minor] = NULL;
 128         mutex_unlock(&phone_lock);
 129 }
 130
 131
 132 static const struct file_operations phone_fops =
 133 {
 134         .owner          = THIS_MODULE,
 135         .open           = phone_open,
 136 };
 137
 138 /*
 139  *      Board init functions
 140  */
 141
 142
 143 /*
 144  *    Initialise Telephony for linux
 145  */
 146
 147 static int __init telephony_init(void)
 148 {
 149         printk(KERN_INFO "Linux telephony interface: v1.00\n");
 150         if (register_chrdev(PHONE_MAJOR, "telephony", &phone_fops)) {
 151                 printk("phonedev: unable to get major %d\n", PHONE_MAJOR);
 152                 return -EIO;
 153         }
 154
 155         return 0;
 156 }
 157
 158 static void __exit telephony_exit(void)
 159 {
 160         unregister_chrdev(PHONE_MAJOR, "telephony");
 161 }
 162
 163 module_init(telephony_init);
 164 module_exit(telephony_exit);
 165
 166 MODULE_LICENSE("GPL");
 167
 168 EXPORT_SYMBOL(phone_register_device);
 169 EXPORT_SYMBOL(phone_unregister_device);