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)