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

January 16, 2006 FREEB(9F)