LXR linux/drivers/tty/n

   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 int n_null_open(struct tty_struct *tty)
  14{
  15        return 0;
  16}
  17
  18static void n_null_close(struct tty_struct *tty)
  19{
  20}
  21
  22static ssize_t n_null_read(struct tty_struct *tty, struct file *file,
  23                           unsigned char __user * buf, size_t nr)
  24{
  25        return -EOPNOTSUPP;
  26}
  27
  28static ssize_t n_null_write(struct tty_struct *tty, struct file *file,
  29                            const unsigned char *buf, size_t nr)
  30{
  31        return -EOPNOTSUPP;
  32}
  33
  34static void n_null_receivebuf(struct tty_struct *tty,
  35                                 const unsigned char *cp, char *fp,
  36                                 int cnt)
  37{
  38}
  39
  40static struct tty_ldisc_ops null_ldisc = {
  41        .owner          =       THIS_MODULE,
  42        .magic          =       TTY_LDISC_MAGIC,
  43        .name           =       "n_null",
  44        .open           =       n_null_open,
  45        .close          =       n_null_close,
  46        .read           =       n_null_read,
  47        .write          =       n_null_write,
  48        .receive_buf    =       n_null_receivebuf
  49};
  50
  51static int __init n_null_init(void)
  52{
  53        BUG_ON(tty_register_ldisc(N_NULL, &null_ldisc));
  54        return 0;
  55}
  56
  57static void __exit n_null_exit(void)
  58{
  59        tty_unregister_ldisc(N_NULL);
  60}
  61
  62module_init(n_null_init);
  63module_exit(n_null_exit);
  64
  65MODULE_LICENSE("GPL");
  66MODULE_AUTHOR("Alan Cox");
  67MODULE_ALIAS_LDISC(N_NULL);
  68MODULE_DESCRIPTION("Null ldisc driver");
  69