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dma_get_private(9r)
NAME
  dma_get_private - General: Gets a data element from the DMA private storage
  space

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


  int dma_get_private(
	  dma_handle_t dma_handle,
	  int index,
	  u_long *data );

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.

  index
      Specifies an index to the DMA private storage area for an internal
      kernel data structure associated with this DMA handle. Currently, you
      can pass only the value zero (0) as the index.

  data
      Specifies the address of the location to retrieve the 64-bit data
      element from the DMA private storage area. You put this 64-bit data
      element in the DMA private storage area in a previous call to
      dma_put_private.

DESCRIPTION
  The dma_get_private interface retrieves a 64-bit data element from the DMA
  private storage area of the internal kernel data structure associated with
  the specified DMA handle. Device drivers can put a 64-bit data element in
  the DMA private storage area of this internal kernel data structure by
  calling dma_put_private. Currently, the internal kernel data structure
  provides only one member to store a 64-bit data element.

  DMA engines that make multiple calls to dma_map_alloc and dma_map_load can
  use the dma_get_private and dma_put_private pair of interfaces. Each call
  to dma_map_alloc and dma_map_load returns the address of the allocated DMA
  handle. The device driver calls dma_put_private to store each returned
  address as the 64-bit data element in each internal kernel data structure's
  DMA private storage area. By storing each address as the 64-bit data
  element in each internal kernel data structure's DMA private storage area,
  the device driver creates a linked list of DMA handles that it can pass to
  some lower software layer. This lower software layer then calls
  dma_get_private to retrieve the resources contained in the linked list of
  DMA handles.



NOTES
  Use of the dma_get_private 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
  Upon successful completion, dma_get_private returns the value zero (0). If
  the index to the private storage area is greater than zero (0),
  dma_get_private returns the value 1, indicating a failure status.

SEE ALSO
  Kernel Interfaces: dma_put_private(9r)

  Data Structures: sg_entry(9s)

Index for Section 9

Alphabetical listing for D

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