xref: /xnu-8792.61.2/bsd/dev/i386/cons.c (revision 42e220869062b56f8d7d0726fd4c88954f87902c)

/*
 * Copyright (c) 2000-2006 Apple Computer, Inc. All rights reserved.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
 *
 * This file contains Original Code and/or Modifications of Original Code
 * as defined in and that are subject to the Apple Public Source License
 * Version 2.0 (the 'License'). You may not use this file except in
 * compliance with the License. The rights granted to you under the License
 * may not be used to create, or enable the creation or redistribution of,
 * unlawful or unlicensed copies of an Apple operating system, or to
 * circumvent, violate, or enable the circumvention or violation of, any
 * terms of an Apple operating system software license agreement.
 *
 * Please obtain a copy of the License at
 * http://www.opensource.apple.com/apsl/ and read it before using this file.
 *
 * The Original Code and all software distributed under the License are
 * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
 * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
 * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
 * Please see the License for the specific language governing rights and
 * limitations under the License.
 *
 * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
 */

/*
 * Indirect driver for console
 *
 * The purpose of this driver is to provide a device node indirection for
 * the console device, which can be any tty class device.  It does this by
 * externalizing a global pointer "constty", which is then pointed at the
 * console tty device.
 *
 * The default for this pointer is uninitialized; when it is NULL, we fall
 * back to the "km" device, which is a tty BSD wrapper device for the
 * Platform Expert console device.  When it is non-NULL, we call through
 * to the tty device device instead.
 *
 * The registration for this device node is static, and the devfs init
 * code does not externalize a named device for it, to avoid software
 * seeing the device and trying to open it.
 *
 * The upshot of this is that the console driver should not be set as your
 * controlling tty, since you will get a reference to a device which does
 * not have an actual device node in /dev, so its name cannot be looked up.
 */
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/conf.h>
#include <sys/ioctl.h>
#include <sys/tty.h>
#include <sys/proc.h>
#include <sys/uio.h>

struct tty      *constty;               /* current console device */

/*
 * The km driver supplied the default console device for the systems
 * (usually a raw frame buffer driver, but potentially a serial driver).
 */
extern struct tty *km_tty[1];

/*
 * cdevsw[] entries for the console device driver
 */
int cnopen(__unused dev_t dev, int flag, int devtype, proc_t pp);
int cnclose(__unused dev_t dev, int flag, int mode, proc_t pp);
int cnread(__unused dev_t dev, struct uio *uio, int ioflag);
int cnwrite(__unused dev_t dev, struct uio *uio, int ioflag);
int cnioctl(__unused dev_t dev, u_long cmd, caddr_t addr, int flg, proc_t p);
int cnselect(__unused dev_t dev, int flag, void * wql, proc_t p);

static dev_t
cndev(void)
{
	if (constty) {
		return constty->t_dev;
	} else {
		return km_tty[0]->t_dev;
	}
}

int
cnopen(__unused dev_t dev, int flag, int devtype, struct proc *pp)
{
	dev = cndev();
	return (*cdevsw[major(dev)].d_open)(dev, flag, devtype, pp);
}


int
cnclose(__unused dev_t dev, int flag, int mode, struct proc *pp)
{
	dev = cndev();
	return (*cdevsw[major(dev)].d_close)(dev, flag, mode, pp);
}


int
cnread(__unused dev_t dev, struct uio *uio, int ioflag)
{
	dev = cndev();
	return (*cdevsw[major(dev)].d_read)(dev, uio, ioflag);
}


int
cnwrite(__unused dev_t dev, struct uio *uio, int ioflag)
{
	dev = cndev();
	return (*cdevsw[major(dev)].d_write)(dev, uio, ioflag);
}


int
cnioctl(__unused dev_t dev, u_long cmd, caddr_t addr, int flag, struct proc *p)
{
	dev = cndev();
#if 0
	/*
	 * Superuser can always use this to wrest control of console
	 * output from the "virtual" console.
	 *
	 * XXX Unfortunately, this code doesn't do what the author thougt
	 * XXX it did; use of the console device, a TIOCCONS would always
	 * XXX disassociate the console from a virtual terminal and send
	 * XXX it back to the fake tty.
	 */
	if ((unsigned) cmd == TIOCCONS && constty) {
		int error = proc_suser(p);
		if (!error) {
			constty = NULL;
		}
		return error;
	}
#endif  /* 0 */

	return (*cdevsw[major(dev)].d_ioctl)(dev, cmd, addr, flag, p);
}


int
cnselect(__unused dev_t dev, int flag, void *wql, struct proc *p)
{
	dev = cndev();
	return (*cdevsw[major(dev)].d_select)(dev, flag, wql, p);
}