QBUFCALL(9F) Kernel Functions for Drivers QBUFCALL(9F)
qbufcall - call a function when a buffer becomes available
#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);
illumos DDI specific (illumos DDI).
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.
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).
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.
The qbufcall() function can be called from user, interrupt, or kernel
context.
allocb(9F), mt-streams(9F), qprocson(9F), qtimeout(9F),
qunbufcall(9F), quntimeout(9F)
Writing Device Drivers
STREAMS Programming Guide
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)
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 Guide
WARNINGS
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)