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dma_map_unload(9r)
NAME
  dma_map_unload - General: Unloads the system DMA resources

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


  int dma_map_unload(
	  int flags,
	  dma_handle_t dma_handle );

ARGUMENTS
  flags
      To cause a deallocation of DMA mapping resources, you set the first
      argument to the special condition bit DMA_DEALLOC.  This bit setting is
      analogous to setting the dma_handle_p argument to the value zero (0)
      for dma_map_load to allocate the DMA mapping resources.

  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_map_unload interface unloads (invalidates) the resources that were
  loaded and set up in a previous call to dma_map_load. A call to
  dma_map_unload does not release or deallocate the resources that were
  allocated in a previous call to dma_map_alloc unless the driver sets the
  flags argument to the DMA_DEALLOC bit.

NOTES
  Use of the dma_map_unload 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.

EXAMPLE
  See Writing Device Drivers: Tutorial for a code example of the
  dma_map_unload interface.





RETURN VALUES
  Upon successful completion, dma_map_unload returns the value 1. Otherwise,
  it returns the value zero (0).


SEE ALSO
  Kernel Interfaces: dma_map_alloc(9r), dma_map_dealloc(9r), dma_map_load(9r)

  Data Structures: sg_entry(9s)

Index for Section 9

Alphabetical listing for D

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