xref: /src/sys/dev/nullcons_subr.c

/*	$NetBSD: nullcons_subr.c,v 1.13 2014/07/25 08:10:35 dholland Exp $	*/

/*-
 * Copyright (c) 2003 The NetBSD Foundation, Inc.
 * 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.
 *
 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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.
 */

#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: nullcons_subr.c,v 1.13 2014/07/25 08:10:35 dholland Exp $");

#include <sys/param.h>
#include <sys/proc.h>
#include <sys/systm.h>
#include <sys/buf.h>
#include <sys/ioctl.h>
#include <sys/tty.h>
#include <sys/file.h>
#include <sys/conf.h>
#include <sys/vnode.h>

#include <dev/cons.h>

static struct tty *nulltty;		/* null console tty */

cons_decl(null);

dev_type_read(nullcndev_read);
dev_type_ioctl(nullcndev_ioctl);
dev_type_tty(nullcndev_tty);

static int	nullcons_newdev(struct consdev *);

const struct cdevsw nullcn_devsw = {
	.d_open = nullopen,
	.d_close = nullclose,
	.d_read = nullcndev_read,
	.d_write = nullwrite,
	.d_ioctl = nullcndev_ioctl,
	.d_stop = nullstop,
	.d_tty = nullcndev_tty,
	.d_poll = nopoll,
	.d_mmap = nommap,
	.d_kqfilter = ttykqfilter,
	.d_discard = nodiscard,
	.d_flag = D_TTY
};

/*
 * null console device. We need it because of the ioctl() it handles,
 * which in particular allows control terminal allocation through
 * TIOCSCTTY ioctl. Without the latter, system won't even boot past init(8)
 * invocation.
 */
int
nullcndev_read(dev_t dev, struct uio *uio, int flag)
{

	return EIO;
}

int
nullcndev_ioctl(dev_t dev, u_long cmd, void *data, int flag, struct lwp *l)
{
	int error;

	error = (*nulltty->t_linesw->l_ioctl)(nulltty, cmd, data, flag, l);
	if (error != EPASSTHROUGH)
		return error;

	error = ttioctl(nulltty, cmd, data, flag, l);
	if (error != EPASSTHROUGH)
		return error;

	return 0;
}

struct tty*
nullcndev_tty(dev_t dev)
{

	return nulltty;
}

/*
 * Mark console as no-op (null) console. Proper initialization is deferred
 * to nullconsattach().
 */
void
nullcnprobe(struct consdev *cn)
{

	cn->cn_pri = CN_NULL;
	cn->cn_dev = NODEV;
}

/*
 * null console initialization. This includes allocation of a new device and
 * a new tty.
 */
void
nullcninit(struct consdev *cn)
{
	static struct consdev nullcn = cons_init(null);

	nullcnprobe(&nullcn);
	cn_tab = &nullcn;
}

/*
 * Dumb getc() implementation. Simply blocks on call.
 */
int
nullcngetc(dev_t dev)
{

	for (;;)
		;
	return 0;
}

/*
 * Dumb putc() implementation.
 */
void
nullcnputc(dev_t dev, int c)
{

}

/*
 * Allocate a new console device and a tty to handle console ioctls.
 */
int
nullcons_newdev(struct consdev *cn)
{
	int error;
	int bmajor = -1, cmajor = -1;

	if ((cn == NULL) || (cn->cn_pri != CN_NULL) || (cn->cn_dev != NODEV))
		return 0;

	/*
	 * Attach no-op device to the device list.
	 */
	error = devsw_attach("nullcn", NULL, &bmajor, &nullcn_devsw, &cmajor);
	if (error != 0)
		return error;

	/*
	 * Allocate tty (mostly to have sane ioctl()).
	 */
	nulltty = tty_alloc();
	nulltty->t_dev = makedev(cmajor, 0);
	tty_attach(nulltty);
	cn->cn_dev = nulltty->t_dev;

	return 0;
}

/*
 * Pseudo-device attach function -- it's the right time to do the rest of
 * initialization.
 */
void
nullconsattach(int pdev_count)
{

	nullcons_newdev(cn_tab);
}