ddi_dma_nextseg(9F)

NAME

     ddi_dma_nextseg - get next DMA segment

SYNOPSIS

     #include <sys/ddi.h>
     #include <sys/sunddi.h>

     int ddi_dma_nextseg(ddi_dma_win_t  win,  ddi_dma_seg_t  seg,
     ddi_dma_seg_t *nseg);

INTERFACE LEVEL

     This interface is obsolete. ddi_dma_nextcookie(9F) should be
     used instead.

PARAMETERS

     win   A DMA window.

     seg   The current  DMA segment or NULL.

     nseg  A pointer to the next DMA segment to be filled in.  If
           seg is NULL, a pointer to the first segment within the
           specified window is returned.

DESCRIPTION

     ddi_dma_nextseg() gets  the  next  DMA  segment  within  the
     specified  window  win.  If the current segment is NULL, the
     first DMA segment within the window is returned.

     A DMA segment is always required for a DMA  window.   A  DMA
     segment  is  a  contiguous  portion  of  a  DMA  window (see
     ddi_dma_nextwin(9F)) which is entirely  addressable  by  the
     device for a data transfer operation.

     An example where multiple  DMA  segments  are  allocated  is
     where  the system does not contain DVMA capabilities and the
     object may be non-contiguous. In  this  example  the  object
     will be broken into smaller contiguous DMA segments. Another
     example is where the device  has   an  upper  limit  on  its
     transfer  size  (for  example an 8-bit address register) and
     has  expressed  this  in  the  DMA  limit   structure   (see
     ddi_dma_lim_sparc(9S) or ddi_dma_lim_x86(9S)). In this exam-
     ple the object will be broken into smaller  addressable  DMA
     segments.

RETURN VALUES

     ddi_dma_nextseg() returns:

     DDI_SUCCESS
           Successfully filled in the next segment pointer.

     DDI_DMA_DONE
           There is no next segment. The current segment  is  the
           final segment within the specified window.

     DDI_DMA_STALE
           win does not refer to the currently active window.

CONTEXT

     ddi_dma_nextseg() can be called from user or interrupt  con-
     text.

EXAMPLES

     For an example, see ddi_dma_segtocookie(9F).

ATTRIBUTES

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

     ____________________________________________________________
    |       ATTRIBUTE TYPE        |       ATTRIBUTE VALUE       |
    |_____________________________|_____________________________|
    | Stability Level             | Obsolete                    |
    |_____________________________|_____________________________|

SEE ALSO

     attributes(5),                       ddi_dma_addr_setup(9F),
     ddi_dma_buf_setup(9F),               ddi_dma_nextcookie(9F),
     ddi_dma_nextwin(9F),                ddi_dma_segtocookie(9F),
     ddi_dma_sync(9F),                     ddi_dma_lim_sparc(9S),
     ddi_dma_lim_x86(9S), ddi_dma_req(9S)

     Writing Device Drivers