ddi_dma_nextseg(9f)

1ddi_dma_nextseg(9F)      Kernel Functions for Drivers      ddi_dma_nextseg(9F)
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NAME

6       ddi_dma_nextseg - get next DMA segment
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SYNOPSIS

9       #include <sys/ddi.h>
10       #include <sys/sunddi.h>
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14       int ddi_dma_nextseg(ddi_dma_win_t win, ddi_dma_seg_t seg,
15            ddi_dma_seg_t *nseg);
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INTERFACE LEVEL

19       This  interface  is  obsolete.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

23       win     A DMA window.
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26       seg     The current DMA segment or NULL.
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29       nseg    A pointer to the next DMA segment to be filled in.  If  seg  is
30               NULL,  a pointer to the first segment within the specified win‐
31               dow is returned.
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DESCRIPTION

35       The ddi_dma_nextseg() function gets the next  DMA  segment  within  the
36       specified  window  win.  If  the current segment is NULL, the first DMA
37       segment within the window is returned.
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40       A DMA segment is always required for a DMA window.  A DMA segment is  a
41       contiguous  portion of a DMA window (see  ddi_dma_nextwin(9F)) which is
42       entirely addressable by the device for a data transfer operation.
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45       An example where multiple DMA segments are allocated is where the  sys‐
46       tem  does  not contain DVMA capabilities and the object may be non-con‐
47       tiguous. In this example the object will be broken  into  smaller  con‐
48       tiguous DMA segments. Another example is where the device has  an upper
49       limit on its transfer size (for example an 8-bit address register)  and
50       has    expressed    this    in    the    DMA   limit   structure   (see
51       ddi_dma_lim_sparc(9S) or  ddi_dma_lim_x86(9S)).  In  this  example  the
52       object will be broken into smaller addressable DMA segments.
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RETURN VALUES

55       The ddi_dma_nextseg() function returns:
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57       DDI_SUCCESS      Successfully filled in the next segment pointer.
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60       DDI_DMA_DONE     There  is  no next segment. The current segment is the
61                        final segment within the specified window.
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64       DDI_DMA_STALE    win does not refer to the currently active window.
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CONTEXT

68       The ddi_dma_nextseg() function can be called from user,  interrupt,  or
69       kernel context.
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EXAMPLES

72       For an example, see ddi_dma_segtocookie(9F).
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ATTRIBUTES

75       See attributes(5) for a description of the following attributes:
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80       ┌─────────────────────────────┬─────────────────────────────┐
81       │      ATTRIBUTE TYPE         │      ATTRIBUTE VALUE        │
82       ├─────────────────────────────┼─────────────────────────────┤
83       │Stability Level              │Obsolete                     │
84       └─────────────────────────────┴─────────────────────────────┘
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