QBUFCALL(9F) Kernel Functions for Drivers QBUFCALL(9F)
NAME
qbufcall - call a function when a buffer becomes available
SYNOPSIS
#include <sys/stream.h>
#include <sys/ddi.h>
bufcall_id_t qbufcall(
queue_t *q,
size_t size,
uint_t pri,
void(
*func)(
void *arg),
void *arg);
INTERFACE LEVEL
illumos DDI specific (illumos DDI).
PARAMETERS
q Pointer to
STREAMS queue structure.
size Number of bytes required for the buffer.
pri Priority of the
allocb(9F) allocation request (not used).
func Function or driver routine to be called when a buffer becomes
available.
arg Argument to the function to be called when a buffer becomes
available.
DESCRIPTION
The
qbufcall() function serves as a
qtimeout(9F) call of
indeterminate length. When a buffer allocation request fails,
qbufcall() can be used to schedule the routine
func to be called with
the argument
arg when a buffer becomes available.
func may call
allocb() or it may do something else.
The
qbufcall() function is tailored to be used with the enhanced
STREAMS framework interface, which is based on the concept of
perimeters. (See
mt-streams(9F).)
qbufcall() schedules the specified
function to execute after entering the perimeters associated with the
queue passed in as the first parameter to
qbufcall(). All outstanding
timeouts and bufcalls must be cancelled (using, respectively,
quntimeout(9F) and
qunbufcall(9F)) before a driver close routine can
block and before the close routine calls
qprocsoff(9F).
qprocson(9F) must be called before calling either
qbufcall() or
qtimeout(9F).
RETURN VALUES
If successful, the
qbufcall() function returns a
qbufcall ID that can
be used in a call to
qunbufcall(9F) to cancel the request. If the
qbufcall() scheduling fails,
func is never called and
0 is returned.
CONTEXT
The
qbufcall() function can be called from user, interrupt, or kernel
context.
SEE ALSO
allocb(9F),
mt-streams(9F),
qprocson(9F),
qtimeout(9F),
qunbufcall(9F),
quntimeout(9F) Writing Device Drivers STREAMS Programming GuideWARNINGS
Even when
func is called by
qbufcall(),
allocb(9F) can fail if
another module or driver had allocated the memory before
func was
able to call
allocb(9F).
January 16, 2006 QBUFCALL(9F)
