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

DEFINITIONS

1. zero_read
2. zero_write
3. zero_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  * zero.c - zero device
  32  */
  34 #include <driver.h>
  36 static int zero_read(device_t, char *, size_t *, int);
  37 static int zero_write(device_t, char *, size_t *, int);
  38 static int zero_init(struct driver *);
  40 static struct devops zero_devops = {
  41         /* open */      no_open,
  42         /* close */     no_close,
  43         /* read */      zero_read,
  44         /* write */     zero_write,
  45         /* ioctl */     no_ioctl,
  46         /* devctl */    no_devctl,
  47 };
  49 struct driver zero_driver = {
  50         /* name */      "zero",
  51         /* devops */    &zero_devops,
  52         /* devsz */     0,
  53         /* flags */     0,
  54         /* probe */     NULL,
  55         /* init */      zero_init,
  56         /* shutdown */  NULL,
  57 };
  59 /*
  60  * Reading from this device will just fill the buffer with zero.
  61  */
  62 static int
zero_read(device_t dev, char *buf, size_t *nbyte, int blkno)
  64 {
  65         void *p;
  67         /* Translate buffer address to kernel address. */
  68         if ((p = kmem_map(buf, *nbyte)) == NULL)
  69                 return EFAULT;
memset(p, 0, *nbyte);
  72         return 0;
  73 }
  75 /*
  76  * Writing data to this device is ignored.
  77  */
  78 static int
zero_write(device_t dev, char *buf, size_t *nbyte, int blkno)
  80 {
  82         return 0;
  83 }
  85 static int
zero_init(struct driver *self)
  87 {
device_create(self, "zero", D_CHR);
  90         return 0;
  91 }