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vba_dma(9r)
NAME
  vba_dma - VMEbus: Performs Master Block Transfers with local DMA

SYNOPSIS
  #include <io/dec/vme/vbareg.h>


  u_long vba_dma(
	  struct controller *ctlr_p,
	  dma_handle_t dma_handle );

ARGUMENTS
  ctlr_p
      Specifies a pointer to the VMEbus device's controller data structure.
      The routine uses this pointer to obtain bus-specific routines and data
      structures that it needs to perform the Master Block Transfer (MBLT)
      data transfer.

  dma_handle
      Specifies a handle to DMA resources associated with the mapping of an
      in-memory I/O buffer onto the VMEbus.

DESCRIPTION
  If the VMEbus adapter provides a master block transfer local DMA engine,
  the vba_dma() routine performs the transfer through DMA.  If the hardware
  does not support a local DMA engine, vba_dma() either performs the transfer
  through programmed I/O or returns an error indication.

  The VMEbus adapter support code may segment the transfer depending on the
  block-mode DMA hardware limitations. Further segmentation may occur
  depending on the amount of physically contiguous memory pages found in the
  virtual buffer supplied to dma_map_load().

NOTES
  You must invoke the following routines with the appropriate specification
  of flags:

    ·  vba_set_dma_addr()

       Specify the VMEbus and DMA flags along with the VMEbus address. You
       must uniquely specify the flags DMA_IN (read from VMEbus to memory) or
       DMA_OUT (write from memory to VMEbus). These flag bits indicate to
       dma_map_alloc() and dma_map_load() that a local DMA engine will be
       used.

    ·  dma_map_alloc()

       Allocates resources for DMA data transfers.

    ·  dma_map_load()

       Loads and sets allocated DMA resources and sets up a DMA data path for
       DMA data transfers.

    ·  vba_dma()

       Performs the actual DMA or I/O copy transfer.

    ·  dma_map_unload()

       Unloads the system DMA resources.

    ·  dma_map_dealloc()

       Releases and deallocates the DMA resources previously allocated for
       DMA data transfers.

RETURN VALUES
  Upon successful completion, vba_dma() returns the number of bytes
  transferred. This value should agree with the byte count value specified in
  the call to dma_map_load(). If it does not, then an error occurred during
  the transfer.

  If you specify DMA_SLEEP in the flags argument of either dma_map_alloc() or
  dma_map_load(), then vba_dma() will wait for the DMA resource if it is
  currently active. Access to the DMA hardware is single threaded at this
  point. If you do not specify DMA_SLEEP and vba_dma() is active, the value
  -1 is returned to indicate that vba_dma() is active. The value -1 is also
  returned if the VMEbus adapter does not supply support code for this
  function.

EXAMPLE
  See the description of master block transfers with local DMA in the System
  Configuration Supplement: OEM Platforms for an example of the use of
  vba_dma().  Also, the driver example chapter of Writing VMEbus Device
  Drivers shows how the dmaex example device driver calls vba_dma() to
  initiate block DMA transfers.

SEE ALSO
  Data Structures: controller(9s)

  Kernel Routines: dma_map_alloc(9r), dma_map_dealloc(9r), dma_map_load(9r),
  dma_map_unload(9r), vba_set_dma_addr(9r)

Index for Section 9

Alphabetical listing for V

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