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Initial revision

/*-
 * Copyright (c) 2005-2006, Kohsuke Ohtani
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the author nor the names of any co-contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

/*
 * zero.c - zero device
 */

#include <driver.h>

static int zero_read(device_t, char *, size_t *, int);
static int zero_write(device_t, char *, size_t *, int);
static int zero_init(void);

/*
 * Driver structure
 */
struct driver zero_drv = {
	/* name */	"Zero device",
	/* order */	2,
	/* init */	zero_init,
};

/*
 * Device I/O table
 */
static struct devio zero_io = {
	/* open */	NULL,
	/* close */	NULL,
	/* read */	zero_read,
	/* write */	zero_write,
	/* ioctl */	NULL,
	/* event */	NULL,
};

static device_t zero_dev;	/* Device object */

/*
 * Read
 */
static int
zero_read(device_t dev, char *buf, size_t *nbyte, int blkno)
{
	void *kbuf;

	/* Translate buffer address to kernel address */
	kbuf = kmem_map(buf, *nbyte);
	if (kbuf == NULL)
		return EFAULT;
	memset(kbuf, 0, *nbyte);
	return 0;
}

/*
 * Writing data to this device is ignored.
 */
static int
zero_write(device_t dev, char *buf, size_t *nbyte, int blkno)
{

	return 0;
}


/*
 * Initialize
 */
static int
zero_init(void)
{

	/* Create device object */
	zero_dev = device_create(&zero_io, "zero", DF_CHR);
	ASSERT(zero_dev);
	return 0;
}