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

Solaris DDI specific (Solaris DDI).

ARGUMENTS

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 example 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 context.

EXAMPLES

For an example see ddi_dma_segtocookie(9F).

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