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

NAME

       freeb - free a message block

SYNOPSIS

       #include <sys/stream.h>

       void  freeb(mblk_t *bp);

PARAMETERS

       bp	Pointer to the message block to be deallocated. mblk_t is an instance of the  msgb(9S) structure.

INTERFACE LEVEL

       Architecture independent level 1 (DDI/DKI).

DESCRIPTION

       freeb()	deallocates  a message block. If the reference count of the  db_ref member of the  datab(9S) structure is greater than	1, freeb()
       decrements the count. If  db_ref equals	1, it deallocates the message block and the corresponding data block and buffer.

       If the data buffer to be freed was allocated with the  esballoc(9F), the buffer may be a non-STREAMS resource. In  that	case,  the  driver
       must  be notified that the attached data buffer needs to be freed, and run its own freeing routine. To make this process independent of the
       driver used in the stream, freeb() finds the  free_rtn(9S) structure associated with the buffer. The  free_rtn structure contains a pointer
       to  the	driver-dependent  routine, which releases the buffer. Once this is accomplished, freeb() releases the STREAMS resources associated
       with the buffer.

CONTEXT

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

EXAMPLES

       Example 1: Using freeb()

       See copyb(9F) for an example of using freeb().

SEE ALSO

       allocb(9F), copyb(9F), dupb(9F), esballoc(9F), free_rtn(9S)

       Writing Device Drivers

       STREAMS Programming Guide

SunOS 5.10							    13 Nov 2000 							 freeb(9F)