arch/um/drivers/null.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Copyright (C) 2002 - 2007 Jeff Dike (jdike@{linux.intel,addtoit}.com)
   4  */
   5
   6 #include <stddef.h>
   7 #include <errno.h>
   8 #include <fcntl.h>
   9 #include "chan_user.h"
  10 #include <os.h>
  11
  12 /* This address is used only as a unique identifier */
  13 static int null_chan;
  14
  15 static void *null_init(char *str, int device, const struct chan_opts *opts)
  16 {
  17         return &null_chan;
  18 }
  19
  20 static int null_open(int input, int output, int primary, void *d,
  21                      char **dev_out)
  22 {
  23         int fd;
  24
  25         *dev_out = NULL;
  26
  27         fd = open(DEV_NULL, O_RDWR);
  28         return (fd < 0) ? -errno : fd;
  29 }
  30
  31 static int null_read(int fd, char *c_out, void *unused)
  32 {
  33         return -ENODEV;
  34 }
  35
  36 static void null_free(void *data)
  37 {
  38 }
  39
  40 const struct chan_ops null_ops = {
  41         .type           = "null",
  42         .init           = null_init,
  43         .open           = null_open,
  44         .close          = generic_close,
  45         .read           = null_read,
  46         .write          = generic_write,
  47         .console_write  = generic_console_write,
  48         .window_size    = generic_window_size,
  49         .free           = null_free,
  50         .winch          = 0,
  51 };