1// SPDX-License-Identifier: GPL-2.0 2#include <linux/types.h> 3#include <linux/errno.h> 4#include <linux/tty.h> 5#include <linux/module.h> 6 7/* 8 * n_null.c - Null line discipline used in the failure path 9 * 10 * Copyright (C) Intel 2017 11 */ 12 13static ssize_t n_null_read(struct tty_struct *tty, struct file *file, u8 *buf, 14 size_t nr, void **cookie, unsigned long offset) 15{ 16 return -EOPNOTSUPP; 17} 18 19static ssize_t n_null_write(struct tty_struct *tty, struct file *file, 20 const u8 *buf, size_t nr) 21{ 22 return -EOPNOTSUPP; 23} 24 25static struct tty_ldisc_ops null_ldisc = { 26 .owner = THIS_MODULE, 27 .num = N_NULL, 28 .name = "n_null", 29 .read = n_null_read, 30 .write = n_null_write, 31}; 32 33static int __init n_null_init(void) 34{ 35 BUG_ON(tty_register_ldisc(&null_ldisc)); 36 return 0; 37} 38 39static void __exit n_null_exit(void) 40{ 41 tty_unregister_ldisc(&null_ldisc); 42} 43 44module_init(n_null_init); 45module_exit(n_null_exit); 46 47MODULE_LICENSE("GPL"); 48MODULE_AUTHOR("Alan Cox"); 49MODULE_ALIAS_LDISC(N_NULL); 50MODULE_DESCRIPTION("Null ldisc driver"); 51