close(D2) close(D2)
NAME
close - relinquish access to a device
SYNOPSIS
Block and Character Synopsis
#include <sys/types.h>
#include <sys/file.h>
#include <sys/errno.h>
#include <sys/open.h>
#include <sys/cred.h>
#include <sys/ddi.h>
int prefixclose(dev_t dev, int flag, int otyp, cred_t *crp);
Block and Character Arguments
dev Device number.
flag File status flags.
otyp Parameter supplied so that the driver can determine
how many times a device was opened and for what
reasons.
crp Pointer to the user credential structure.
STREAMS Synopsis
#include <sys/types.h>
#include <sys/stream.h>
#include <sys/file.h>
#include <sys/errno.h>
#include <sys/cred.h>
#include <sys/ddi.h>
int prefixclose(queue_t *q, int flag, cred_t *crp);
STREAMS Arguments
q Pointer to queue used to reference the read side of
the driver.
flag File status flag.
crp Pointer to the user credential structure.
DESCRIPTION
Block and Character Description
The close routine ends the connection between the user process
and the device, and prepares the device (hardware and
software) so that it is ready to be opened again.
Copyright 1994 Novell, Inc. Page 1
close(D2) close(D2)
Valid values for flag and their definitions can be found in
open(D2).
The values for otyp are mutually exclusive:
OTYP_BLK Close was through the block interface for
the device.
OTYP_CHR Close was through the raw/character
interface for the device.
OTYP_LYR Close a layered device. This flag is used
when one driver calls another driver's close
routine.
For OTYP_BLK and OTYP_CHR, a device may be opened
simultaneously by multiple processes and the driver open
routine is called for each open, but the kernel will only call
the close routine when the last process using the device
issues a close(2) system call or exits.
There is one exception to this rule. If a device is opened
through both its character and its block interfaces, then
there will be one close per interface. For example, if the
same device is opened twice through its block interface and
three times through its character interface, then there will
be two calls to the driver's close routine; one when the block
interface is finished being used, and one when the character
interface is finished being used.
For OTYP_LYR, there will be one such close for every
corresponding open. Here, the driver should count each open
and close based on the otyp parameter to determine when the
device should really be closed.
STREAMS Description
The close routines of STREAMS drivers and modules are called
when a stream is dismantled or a module popped. The steps for
dismantling a stream are performed in the following order.
First, any non-persistent multiplexor links present are
unlinked and the lower streams are closed. Next, the
following steps are performed for each module or driver on the
stream, starting at the head and working toward the tail:
Copyright 1994 Novell, Inc. Page 2
close(D2) close(D2)
1. The write queue is given a chance to drain.
2. Interrupts from STREAMS devices are blocked.
3. The close routine is called.
4. The module or driver is removed from the stream.
5. Any remaining messages on the queues are freed.
Return Values
The close routine should return 0 for success, or the
appropriate error number. Refer to errnos(D5) for a list of
DDI/DKI error numbers. Return errors rarely occur, but if a
failure is detected, the driver should still close the device
and then decide whether the severity of the problem warrants
displaying a message on the console.
USAGE
This entry point is required in all drivers and STREAMS
modules.
A close routine could perform any of the following general
functions, depending on the type of device and the service
provided:
disable device interrupts
hang up phone lines
rewind a tape
deallocate buffers from a private buffering scheme
unlock an unsharable device (that was locked in the open
routine)
flush buffers
notify a device of the close
cancel any pending timeout or bufcall routines that
access data that are deinitialized or deallocated during
close
Copyright 1994 Novell, Inc. Page 3
close(D2) close(D2)
deallocate any resources allocated on open
Multithreaded STREAMS drivers and modules must call
qprocsoff(D3) to disable their put(D2) and service [srv(D2)]
routines before returning from the close routine.
Synchronization Constraints
The close routine has user context and can sleep. However,
STREAMS drivers and modules must sleep such that signals do
not cause the sleep to longjump [see sleep(D3)]. Also, if a
close routine does sleep, it is important that the driver
writer synchronize the driver's open and close routines, since
a driver can be reopened while being closed.
If the FNDELAY or FNONBLOCK flags are specified in the flag
argument, the driver should try to avoid sleeping, if
possible, during close processing.
REFERENCES
drv_priv(D3), errnos(D5), qprocsoff(D3), open(D2), queue(D4),
unbufcall(D3), untimeout(D3), sleep(D3)
NOTICES
Portability
All processors
Applicability
ddi: 1, 2, 3, 4, 5, 5mp, 6, 6mp, 7, 7mp
Copyright 1994 Novell, Inc. Page 4