phonedev.c

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/*
 *            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, <[email protected]>
 *
 * Fixes:       Mar 01 2000 Thomas Sparr, <[email protected]>
 *              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 <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\n");
    if (register_chrdev(PHONE_MAJOR, "telephony", &phone_fops)) {
        printk("phonedev: unable to get major %d\n", 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);