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// SPDX-License-Identifier: GPL-2.0
#include <linux/types.h>
#include <linux/errno.h>
#include <linux/tty.h>
#include <linux/module.h>
/*
* n_null.c - Null line discipline used in the failure path
*
* Copyright (C) Intel 2017
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
*/
static int n_null_open(struct tty_struct *tty)
{
return 0;
}
static void n_null_close(struct tty_struct *tty)
{
}
static ssize_t n_null_read(struct tty_struct *tty, struct file *file,
unsigned char __user * buf, size_t nr)
{
return -EOPNOTSUPP;
}
static ssize_t n_null_write(struct tty_struct *tty, struct file *file,
const unsigned char *buf, size_t nr)
{
return -EOPNOTSUPP;
}
static void n_null_receivebuf(struct tty_struct *tty,
const unsigned char *cp, char *fp,
int cnt)
{
}
static struct tty_ldisc_ops null_ldisc = {
.owner = THIS_MODULE,
.magic = TTY_LDISC_MAGIC,
.name = "n_null",
.open = n_null_open,
.close = n_null_close,
.read = n_null_read,
.write = n_null_write,
.receive_buf = n_null_receivebuf
};
static int __init n_null_init(void)
{
BUG_ON(tty_register_ldisc(N_NULL, &null_ldisc));
return 0;
}
static void __exit n_null_exit(void)
{
tty_unregister_ldisc(N_NULL);
}
module_init(n_null_init);
module_exit(n_null_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("Alan Cox");
MODULE_ALIAS_LDISC(N_NULL);
MODULE_DESCRIPTION("Null ldisc driver");
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