include/sys/open.h

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License, Version 1.0 only
   6  * (the "License").  You may not use this file except in compliance
   7  * with the License.
   8  *
   9  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
  10  * or http://www.opensolaris.org/os/licensing.
  11  * See the License for the specific language governing permissions
  12  * and limitations under the License.
  13  *
  14  * When distributing Covered Code, include this CDDL HEADER in each
  15  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  16  * If applicable, add the following below this CDDL HEADER, with the
  17  * fields enclosed by brackets "[]" replaced with your own identifying
  18  * information: Portions Copyright [yyyy] [name of copyright owner]
  19  *
  20  * CDDL HEADER END
  21  */
  22 /*      Copyright (c) 1984, 1986, 1987, 1988, 1989 AT&T */
  23 /*        All Rights Reserved   */
  24
  25
  26 #ifndef _SYS_OPEN_H
  27 #define _SYS_OPEN_H
  28
  29 #ifdef  __cplusplus
  30 extern "C" {
  31 #endif
  32
  33 /*
  34  * Some drivers need to be able to keep accurate records of open/close
  35  * calls to determine whether a device is still in use.  To allow this
  36  * open/close calls have been typed and the type is passed as a third
  37  * argument in open/close calls, as in:
  38  *      (*cdevsw[getmajor(dev)].d_open)(getminor(dev), flag, OTYP_CHR);
  39  * or
  40  *      (*cdevsw[getmajor(dev)].d_close)(getminor(dev), flag, OTYP_CHR);
  41  * Five types of open/close calls have been defined:
  42  * OTYP_BLK:    open/close of a block special file
  43  * OTYP_MNT:    open/close for mounting/unmounting a file system
  44  * OTYP_CHR:    open/close of a character special file
  45  * OTYP_SWP:    open/close of a swapping device.
  46  * OTYP_LYR:    open/close calls from a driver to another driver,
  47  *              without a file being open for the dev of the lower driver.
  48  *
  49  * The first four types of open/close calls obey the protocol rule
  50  * that many more opens may occur for a given minor(dev) for that type of open,
  51  * but a close call happens only on the last close of that dev.
  52  * This protocol allows a flag to be used (set by opens, cleared by closes)
  53  * to keep track of the state for a given minor device value.
  54  *
  55  * Calls of the fifth type (OTYP_LYR) must obey the protocol rule
  56  * that open and close call calls are always paired.  This protocol
  57  * permits several drivers to be layers above the same device driver.
  58  * A counter can be used for this protocol.
  59  *
  60  * The value OTYPCNT is defined for the purpose of declaring arrays
  61  * in drivers and for performing range checks (0 <= otyp < OTYPCNT)
  62  * on values passed.
  63  */
  64
  65 #define OTYPCNT         5
  66 #define OTYP_BLK        0
  67 #define OTYP_MNT        1
  68 #define OTYP_CHR        2
  69 #define OTYP_SWP        3
  70 #define OTYP_LYR        4
  71
  72 #ifdef  __cplusplus
  73 }
  74 #endif
  75
  76 #endif  /* _SYS_OPEN_H */