drivers/tty/n_null.c

   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");