Kernel Functions for Drivers                   ddidmamovwin(9F)



NAME
     ddidmamovwin - shift current DMA window

SYNOPSIS
     #include 
     #include 



     int ddidmamovwin(ddidmahandlet handle, offt *offp,
          uintt *lenp, ddidmacookiet *cookiep);


INTERFACE LEVEL
     This interface is  obsolete.  ddidmagetwin(9F)  should  be
     used instead.

PARAMETERS
     handle     The  DMA  handle  filled  in   by   a   call   to
                ddidmasetup(9F).


     offp       A pointer to an offset to set the DMA window  to.
                Upon  a  successful  return, it will be filled in
                with the new offset from  the  beginning  of  the
                object resources are allocated for.


     lenp       A pointer to a value which  must  either  be  the
                current  size  of the DMA window (as known from a
                call to ddidmacurwin(9F)  or  from  a  previous
                call  to  ddidmamovwin()).  Upon  a  successful
                return, it will be filled in with  the  size,  in
                bytes, of the current window.


     cookiep    A    pointer    to    a    DMA    cookie     (see
                ddidmacookie(9S)).  Upon  a  successful return,
                cookiep is filled  in  just  as  if  an  implicit
                ddidmahtoc(9F) had been made.


DESCRIPTION
     The ddidmamovwin() function shifts the current DMA window.
     If a DMA request allows the system to allocate resources for
     less than the entire object by setting  the  DIDMAPARTIAL
     flag  in the ddidmareq(9S) structure, the current DMA win-
     dow can be shifted by a call to ddidmamovwin().


     The caller must first determine the current DMA window  size
     by  a  call  to ddidmacurwin(9F). Using the current offset



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Kernel Functions for Drivers                   ddidmamovwin(9F)



     and size  of  the  window  thus  retrieved,  the  caller  of
     ddidmamovwin()  may  change  the window onto the object by
     changing the offset by a value which is some multiple of the
     size of the DMA window.


     The  ddidmamovwin()  function  takes  care  of  underlying
     resource synchronizations required to shift the window. How-
     ever, if you want to access the data prior to or after  mov-
     ing    the    window,    further    synchronizations   using
     ddidmasync(9F) are required.


     This function is normally called from an interrupt  routine.
     The  first  invocation  of  the  DMA engine is done from the
     driver. All subsequent invocations of  the  DMA  engine  are
     done  from  the  interrupt  routine.  The  interrupt routine
     checks to see if the request has been completed. If it  has,
     it  returns without invoking another DMA transfer. Otherwise
     it calls ddidmamovwin() to shift the  current  window  and
     starts another DMA transfer.

RETURN VALUES
     The ddidmamovwin() function returns:

     DISUCES    The current length and offset are  legal  and
                    have been set.


     DIFAILURE    Otherwise.


CONTEXT
     The ddidmamovwin()  function  can  be  called  from  user,
     interrupt, or kernel context.

ATRIBUTES
     See attributes(5) for a description of the following  attri-
     butes:



     
           ATRIBUTE TYPE               ATRIBUTE VALUE       
    
     Stability Level              Obsolete                    
    


SEE ALSO
     attributes(5),    ddidmacurwin(9F),    ddidmagetwin(9F),
     ddidmahtoc(9F),    ddidmasetup(9F),    ddidmasync(9F),



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Kernel Functions for Drivers                   ddidmamovwin(9F)



     ddidmacookie(9S), ddidmareq(9S)


     Writing Device Drivers

WARNINGS
     The caller must guarantee that the  resources  used  by  the
     object are inactive prior to calling this function.















































SunOS 5.11          Last change: 16 Jan 2006                    3