52 lines
2.1 KiB
C
52 lines
2.1 KiB
C
/* Copyright (c) 1984 AT&T */
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/* All Rights Reserved */
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/* THIS IS UNPUBLISHED PROPRIETARY SOURCE CODE OF AT&T */
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/* The copyright notice above does not evidence any */
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/* actual or intended publication of such source code. */
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/*#ident "@(#)kern-port:sys/open.h 10.2"*/
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#ident "$Revision: 3.5 $"
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/* Some drivers need to be able to keep accurate records of open/close
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* calls to determine whether a device is still in use. To allow this
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* open/close calls have been typed and the type is passed as a third
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* argument in open/close calls, as in:
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* (*cdevsw[major(dev)].d_open)(minor(dev), flag, OTYP_CHR);
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* or
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* (*cdevsw[major(dev)].d_close)(minor(dev), flag, OTYP_CHR);
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* Five types of open/close calls have been defined:
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* OTYP_BLK: open/close of a block special file
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* OTYP_MNT: open/close for mounting/unmounting a file system
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* OTYP_CHR: open/close of a character special file
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* OTYP_SWP: open/close of a swapping device.
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* OTYP_LYR: open/close calls from a driver to another driver,
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* without a file being open for the dev of the lower driver.
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*
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* The first four types of open/close calls obey the protocol rule
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* that many more opens may occur for a given minor(dev) for that type of open,
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* but a close call happens only on the last close of that dev.
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* This protocol allows a flag to be used (set by opens, cleared by closes)
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* to keep track of the state for a given minor device value.
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*
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* Calls of the fifth type (OTYP_LYR) must obey the protocol rule
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* that open and close call calls are always paired. This protocol
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* permits several drivers to be layers above the same device driver.
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* A counter can be used for this protocol.
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*
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* OTYP_CLONE is used by the cln2 driver, to let the device open routine
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* know that the open is through the cln2 device (the same way that the
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* streams clone driver uses CLONEOPEN.)
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*
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* The value OTYPCNT is defined for the purpose of declaring arrays
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* in drivers and for performing range checks (0 <= otyp < OTYPCNT)
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* on values passed.
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*/
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#define OTYPCNT 6
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#define OTYP_BLK 0
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#define OTYP_MNT 1
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#define OTYP_CHR 2
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#define OTYP_SWP 3
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#define OTYP_LYR 4
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#define OTYP_CLONE 5
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