freeb(9F) Kernel Functions for Drivers freeb(9F)NAMEfreeb - 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 con‐
text.
EXAMPLES
Example 1: Using freeb()
See copyb(9F) for an example of using freeb().
SEE ALSOallocb(9F), copyb(9F), dupb(9F), esballoc(9F), free_rtn(9S)
Writing Device Drivers
STREAMS Programming Guide
SunOS 5.10 16 Jan 2006 freeb(9F)
