xref: /illumos-gate/usr/src/uts/common/sys/open.h (revision b4203d75)

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*	Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T	*/
/*	  All Rights Reserved	*/


#ifndef _SYS_OPEN_H
#define	_SYS_OPEN_H

#ifdef	__cplusplus
extern "C" {
#endif

/*
 * Some drivers need to be able to keep accurate records of open/close
 * calls to determine whether a device is still in use.  To allow this
 * open/close calls have been typed and the type is passed as a third
 * argument in open/close calls, as in:
 *	(*cdevsw[getmajor(dev)].d_open)(getminor(dev), flag, OTYP_CHR);
 * or
 *	(*cdevsw[getmajor(dev)].d_close)(getminor(dev), flag, OTYP_CHR);
 * Five types of open/close calls have been defined:
 * OTYP_BLK:	open/close of a block special file
 * OTYP_MNT:	open/close for mounting/unmounting a file system
 * OTYP_CHR:	open/close of a character special file
 * OTYP_SWP:	open/close of a swapping device.
 * OTYP_LYR:	open/close calls from a driver to another driver,
 *		without a file being open for the dev of the lower driver.
 *
 * The first four types of open/close calls obey the protocol rule
 * that many more opens may occur for a given minor(dev) for that type of open,
 * but a close call happens only on the last close of that dev.
 * This protocol allows a flag to be used (set by opens, cleared by closes)
 * to keep track of the state for a given minor device value.
 *
 * Calls of the fifth type (OTYP_LYR) must obey the protocol rule
 * that open and close call calls are always paired.  This protocol
 * permits several drivers to be layers above the same device driver.
 * A counter can be used for this protocol.
 *
 * The value OTYPCNT is defined for the purpose of declaring arrays
 * in drivers and for performing range checks (0 <= otyp < OTYPCNT)
 * on values passed.
 */

#define	OTYPCNT		5
#define	OTYP_BLK	0
#define	OTYP_MNT	1
#define	OTYP_CHR	2
#define	OTYP_SWP	3
#define	OTYP_LYR	4

#ifdef	__cplusplus
}
#endif

#endif	/* _SYS_OPEN_H */