Alan Cox | 8a8dabf | 2017-06-02 13:49:30 +0100 | [diff] [blame] | 1 | #include <linux/types.h> |
| 2 | #include <linux/errno.h> |
| 3 | #include <linux/tty.h> |
| 4 | #include <linux/module.h> |
| 5 | |
| 6 | /* |
| 7 | * n_null.c - Null line discipline used in the failure path |
| 8 | * |
| 9 | * Copyright (C) Intel 2017 |
| 10 | * |
| 11 | * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
| 12 | * |
| 13 | * This program is free software; you can redistribute it and/or modify |
| 14 | * it under the terms of the GNU General Public License version 2 |
| 15 | * as published by the Free Software Foundation. |
| 16 | * |
| 17 | * This program is distributed in the hope that it will be useful, |
| 18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | * GNU General Public License for more details. |
| 21 | * |
| 22 | * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ |
| 23 | */ |
| 24 | |
| 25 | static int n_null_open(struct tty_struct *tty) |
| 26 | { |
| 27 | return 0; |
| 28 | } |
| 29 | |
| 30 | static void n_null_close(struct tty_struct *tty) |
| 31 | { |
| 32 | } |
| 33 | |
| 34 | static ssize_t n_null_read(struct tty_struct *tty, struct file *file, |
| 35 | unsigned char __user * buf, size_t nr) |
| 36 | { |
| 37 | return -EOPNOTSUPP; |
| 38 | } |
| 39 | |
| 40 | static ssize_t n_null_write(struct tty_struct *tty, struct file *file, |
| 41 | const unsigned char *buf, size_t nr) |
| 42 | { |
| 43 | return -EOPNOTSUPP; |
| 44 | } |
| 45 | |
| 46 | static void n_null_receivebuf(struct tty_struct *tty, |
| 47 | const unsigned char *cp, char *fp, |
| 48 | int cnt) |
| 49 | { |
| 50 | } |
| 51 | |
| 52 | static struct tty_ldisc_ops null_ldisc = { |
| 53 | .owner = THIS_MODULE, |
| 54 | .magic = TTY_LDISC_MAGIC, |
| 55 | .name = "n_null", |
| 56 | .open = n_null_open, |
| 57 | .close = n_null_close, |
| 58 | .read = n_null_read, |
| 59 | .write = n_null_write, |
| 60 | .receive_buf = n_null_receivebuf |
| 61 | }; |
| 62 | |
| 63 | static int __init n_null_init(void) |
| 64 | { |
| 65 | BUG_ON(tty_register_ldisc(N_NULL, &null_ldisc)); |
| 66 | return 0; |
| 67 | } |
| 68 | |
| 69 | static void __exit n_null_exit(void) |
| 70 | { |
| 71 | tty_unregister_ldisc(N_NULL); |
| 72 | } |
| 73 | |
| 74 | module_init(n_null_init); |
| 75 | module_exit(n_null_exit); |
| 76 | |
| 77 | MODULE_LICENSE("GPL"); |
| 78 | MODULE_AUTHOR("Alan Cox"); |
| 79 | MODULE_ALIAS_LDISC(N_NULL); |
| 80 | MODULE_DESCRIPTION("Null ldisc driver"); |