freebsd man page for wr

WR(9F)							   Kernel Functions for Drivers 						    WR(9F)

NAME

       WR, wr - get pointer to the write queue for this module or driver

SYNOPSIS

       #include <sys/stream.h>
       #include <sys/ddi.h>

       queue_t *WR(queue_t *q);

INTERFACE LEVEL

       Architecture independent level 1 (DDI/DKI).

PARAMETERS

       q	Pointer to the read queue whose  write queue is to be returned.

DESCRIPTION

       The WR() function accepts a read queue pointer as an argument and returns a pointer to the write queue of the same module.

       CAUTION: Make sure the argument to this function is a pointer to a read queue. WR() will not check for queue type, and a system panic could
       result if the pointer is not to a read queue.

RETURN VALUES

       The pointer to the write queue.

CONTEXT

       WR() can be called from user or interrupt context.

EXAMPLES

       Example 1: Using WR()

       In a STREAMS close(9E) routine, the driver or module is passed a pointer to the read queue.  These usually are set to the  address  of  the
       module-specific data structure for the minor device.

       1   xxxclose(q, flag)
       2       queue_t *q;
       3       int flag;
       4   {
       5	     q->q_ptr = NULL;
       6	 WR(q)->q_ptr = NULL;
		     . . .
       7   }

SEE ALSO

       close(9E), OTHERQ(9F), RD(9F)

       Writing Device Drivers

       STREAMS Programming Guide

SunOS 5.10							    15 Nov 1991 							    WR(9F)