// 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 */ 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 *buf, size_t nr, void **cookie, unsigned long offset) { 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, const char *fp, int cnt) { } static struct tty_ldisc_ops null_ldisc = { .owner = THIS_MODULE, .num = N_NULL, .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(&null_ldisc)); return 0; } static void __exit n_null_exit(void) { tty_unregister_ldisc(&null_ldisc); } 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");