SVR5 and SCO OpenServer

close(D2str)

close -- relinquish access to a STREAMS device

Syntax

See close(D2) for DDI syntax, arguments, return values, and basic usage information.

See close(D2oddi) for ODDI syntax, arguments, return values, and basic usage information.

Usage

This entry point is required in all drivers and STREAMS modules.

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:

Any non-persistent multiplexor links present are unlinked and the lower streams are closed.
The following steps are performed for each module or driver on the stream, starting at the head and working toward the tail:
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.

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
deallocate any resources allocated on open

Multithreaded STREAMS drivers and modules must call qprocsoff(D3str) to disable their put(D2str) and service (srv(D2str)) 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 as discussed on the sleep(D3) manual page. 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

close(D2), close(D2mdi), close(D2oddi)

drv_priv(D3), errnos(D5), open(D2str), qprocsoff(D3str), queue(D4str), sleep(D3), unbufcall(D3str), untimeout(D3),