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Introduce null console. This pseudo device acts as a normal console with the

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exception that it discards any output, and is useful for booting the kernel
on headless boxes.
This commit is contained in:
cdi 2003-10-17 20:27:38 +00:00
parent c8c91c50dd
commit 61da4642b8
1 changed files with 207 additions and 0 deletions
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sys/dev/nullcons_subr.c Normal file
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/* $NetBSD: nullcons_subr.c,v 1.1 2003/10/17 20:27:38 cdi 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.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the NetBSD
* Foundation, Inc. and its contributors.
* 4. Neither the name of The NetBSD Foundation nor the names of its
* contributors may be used to endorse or promote products derived
* from this software without specific prior written permission.
*
* 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 1.1 2003/10/17 20:27:38 cdi Exp $");
#include <sys/param.h>
#include <sys/proc.h>
#include <sys/user.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>
extern struct consdev *cn_tab; /* physical console device info */
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 __P((struct consdev *));
const struct cdevsw nullcn_devsw = {
nullopen, nullclose, nullcndev_read, nullwrite, nullcndev_ioctl,
nullstop, nullcndev_tty, nopoll, nommap, ttykqfilter, 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, uio, flag)
dev_t dev;
struct uio *uio;
int flag;
{
for(;;);
return (0);
}
int
nullcndev_ioctl(dev, cmd, data, flag, p)
dev_t dev;
u_long cmd;
caddr_t data;
int flag;
struct proc *p;
{
int error;
error = (*nulltty->t_linesw->l_ioctl)(nulltty, cmd, data, flag, p);
if (error != EPASSTHROUGH)
return (error);
error = ttioctl(nulltty, cmd, data, flag, p);
if (error != EPASSTHROUGH)
return (error);
return (0);
}
struct tty*
nullcndev_tty(dev)
dev_t dev;
{
return nulltty;
}
/*
* Mark console as no-op (null) console. Proper initialization is deferred
* to nullconsattach().
*/
void
nullcnprobe(cn)
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(cn)
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)
dev_t dev;
{
for(;;);
return (0);
}
/*
* Dumb putc() implementation.
*/
void
nullcnputc(dev, c)
dev_t dev;
int c;
{
}
/*
* Allocate a new console device and a tty to handle console ioctls.
*/
int
nullcons_newdev(cn)
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 = ttymalloc();
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(pdev_count)
int pdev_count;
{
nullcons_newdev(cn_tab);
}