Prex Home / Browse Source - Prex Version: 0.9.0

root/bsp/drv/dev/misc/null.c

DEFINITIONS

1. null_read
2. null_write
3. null_init

   1 /*-
   2  * Copyright (c) 2005-2006, Kohsuke Ohtani
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. Neither the name of the author nor the names of any co-contributors
  14  *    may be used to endorse or promote products derived from this software
  15  *    without specific prior written permission.
  16  *
  17  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
  18  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  19  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  20  * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
  21  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  22  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  23  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  24  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  25  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  26  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  27  * SUCH DAMAGE.
  28  */
  30 /*
  31  * null.c - null device
  32  */
  34 #include <driver.h>
  36 static int null_read(device_t, char *, size_t *, int);
  37 static int null_write(device_t, char *, size_t *, int);
  38 static int null_init(struct driver *);
  40 static struct devops null_devops = {
  41         /* open */      no_open,
  42         /* close */     no_close,
  43         /* read */      null_read,
  44         /* write */     null_write,
  45         /* ioctl */     no_ioctl,
  46         /* devctl */    no_devctl,
  47 };
  49 struct driver null_driver = {
  50         /* name */      "null",
  51         /* devops */    &null_devops,
  52         /* devsz */     0,
  53         /* flags */     0,
  54         /* probe */     NULL,
  55         /* init */      null_init,
  56         /* shutdown */  NULL,
  57 };
  59 /*
  60  * Always returns 0 bytes as the read size.
  61  */
  62 static int
null_read(device_t dev, char *buf, size_t *nbyte, int blkno)
  64 {
  66         *nbyte = 0;
  67         return 0;
  68 }
  70 /*
  71  * Data written to this device is discarded.
  72  */
  73 static int
null_write(device_t dev, char *buf, size_t *nbyte, int blkno)
  75 {
  77         return 0;
  78 }
  80 static int
null_init(struct driver *self)
  82 {
device_create(self, "null", D_CHR);
  85         return 0;
  86 }