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 13 static 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 19 static 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 25 static 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 33 static int __init n_null_init(void) 34 { 35 BUG_ON(tty_register_ldisc(&null_ldisc)); 36 return 0; 37 } 38 39 static void __exit n_null_exit(void) 40 { 41 tty_unregister_ldisc(&null_ldisc); 42 } 43 44 module_init(n_null_init); 45 module_exit(n_null_exit); 46 47 MODULE_LICENSE("GPL"); 48 MODULE_AUTHOR("Alan Cox"); 49 MODULE_ALIAS_LDISC(N_NULL); 50 MODULE_DESCRIPTION("Null ldisc driver"); 51