Index for Section 9r

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svatophys(9r)
NAME
  svatophys - General: Converts a system virtual address to a physical
  address

SYNOPSIS
  kern_return_t svatophys(
	  vm_offset_t kern_addr,
	  vm_offset_t *phys_addr );

ARGUMENTS
  kern_addr
      Specifies the kernel virtual address.

  phys_addr
      Specifies a pointer to the physical address to be filled in.

DESCRIPTION
  The svatophys routine converts a system virtual address to the
  corresponding physical address. All address and data structure manipulation
  done within the kernel is performed using system virtual addresses.
  Typically, system virtual addresses are a means of mapping physical memory
  and I/O space, which often consists of device registers and DMA buffers. In
  contrast to this, devices are usually unaware of any virtual addressing and
  for this reason use physical addresses. You use the svatophys routine to
  perform this address translation.

  As an example of where you can use this address translation, a disk device
  driver can use DMA buffers to transfer blocks of data to the disk (for the
  case of a write operation). The data to be written to disk is present in
  system memory at a system virtual address known to the driver. To initiate
  the DMA operation, the disk driver can set up a command packet to specify a
  write operation to the underlying disk controller hardware. This write
  command packet contains (among other things) the location of the DMA buffer
  as a physical address and the length of the buffer. Here, the driver calls
  the svatophys routine to translate the system virtual address of the DMA
  buffer to a physical address in the command packet issued to the disk
  driver.

RETURN VALUES
  The svatophys routine returns the following:

  KERN_SUCCESS
      The address translation has been completed successfully.

  KERN_INVALID_ADDRESS
      Unable to perform address translation. This value indicates that the
      address specified by the kern_addr argument is not a valid kernel or
      system virtual address.

Index for Section 9r

Alphabetical listing for S

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