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


The freeb() function 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


The freeb() function can be called from user, interrupt, or kernel
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

illumos January 16, 2006 FREEB(9F)