qbufcall - call a function when a buffer becomes available
bufcall_id_t qbufcall(queue_t *q, size_t size, uint_t pri,
void(*func)(void *arg), void *arg);
illumos DDI specific (illumos DDI).
Pointer to STREAMS queue structure.
Number of bytes required for the buffer.
Priority of the allocb(9F)
allocation request (not
Function or driver routine to be called when a buffer
Argument to the function to be called when a buffer
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
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
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).