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dma_get_next_sgentry(9r)
NAME
  dma_get_next_sgentry - General: Returns a pointer to the current sg_entry
  and increments an index to point to the next

SYNOPSIS
  #include <io/common/devdriver.h>


  sg_entry_t dma_get_next_sgentry(
	  dma_handle_t dma_handle );

ARGUMENTS
  dma_handle
      Specifies a handle to DMA resources associated with the mapping of an
      in-memory I/O buffer onto a controller's I/O bus. This handle provides
      the information to access bus address/byte count pairs. (A bus
      address/byte count pair is represented by the ba and bc members of an
      sg_entry structure pointer.) Device driver writers can view the DMA
      handle as the tag to the allocated system resources needed to perform a
      DMA operation.

DESCRIPTION
  The dma_get_next_sgentry interface returns a pointer to a bus address/byte
  count pair from the in-kernel DMA mapping data structures.  After each call
  to dma_get_next_sgentry, the interface increments an internal index
  variable. This increment operation ensures that the next call to
  dma_get_next_sgentry gets the next sg_entry pointer and thus the next bus
  address/byte count pair for this DMA handle.	This contrasts with the
  dma_get_curr_sgentry interface, which does not perform an increment
  operation.

NOTES
  Use of the dma_get_next_sgentry interface makes device drivers more
  portable between DMA hardware-mapping implementations across different
  hardware platforms because it masks out any future changes in the kernel-
  and system-level DMA mapping data structures.

RETURN VALUES
  On successful completion, dma_get_next_sgentry returns a pointer to the
  sg_entry structure associated with a mapped region of an I/O buffer on the
  controller's I/O bus. The dma_get_next_sgentry interface returns the value
  0 (zero) to indicate that it has reached the end of the bus address/byte
  count pairs for this DMA handle.





SEE ALSO
  Data Structures: sg_entry(9s)


  Kernel Interfaces: dma_get_curr_sgentry(9r)

Index for Section 9

Alphabetical listing for D

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