Kernel Functions for Drivers                         qbufcall(9F)



NAME
     qbufcall - call a function when a buffer becomes available

SYNOPSIS
     #include 
     #include 



     bufcallidt qbufcall(queuet *q, sizet size, uintt pri,
          void(*func)(void *arg), void *arg);


INTERFACE LEVEL
     Solaris DI specific (Solaris DI).

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



SunOS 5.11          Last change: 16 Jan 2006                    1






Kernel Functions for Drivers                         qbufcall(9F)



     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).
























SunOS 5.11          Last change: 16 Jan 2006                    2