Index for Section 9r

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KSEG_TO_PHYS(9r)
NAME
  KSEG_TO_PHYS - General: Converts a kernel-unmapped virtual address to a
  physical address

SYNOPSIS
  vm_offset_t KSEG_TO_PHYS(
	  vm_offset_t addr );

ARGUMENTS
  addr
      Specifies the buffer virtual address to convert to a physical address.

DESCRIPTION
  The KSEG_TO_PHYS routine converts a kernel-unmapped virtual address to a
  kernel physical address. Device drivers can use this physical address in
  DMA operations. Prior to calling KSEG_TO_PHYS, device driver writers often
  call one of the following routines to determine whether the address passed
  is a virtual address in the addressed kernel segment:

    ·  IS_KSEG_VA

       Determines if the specified address is located in the kernel-unmapped
       address space.

    ·  IS_SEG0_VA

       Determines if the specified address is located in the user-mapped
       address space.

    ·  IS_SEG1_VA

       Determines if the specified address is located in the kernel-mapped
       address space.

RETURN VALUES
  Upon successful completion, KSEG_TO_PHYS returns the physical address.

EXAMPLE
  The following code fragment shows a call to KSEG_TO_PHYS:

       .
       .
       .

       caddr_t virt_addr;  [1]
       unsigned phys_addr; [2]

       .
       .
       .

	   if(IS_KSEG_VA(virt_addr)) { [3]
	       phys_addr = KSEG_TO_PHYS(virt_addr); [4]

       .
       .
       .

   1.  Declares a variable to store the user buffer's virtual address.

   2.  Declares a variable to store the physical address returned by
       KSEG_TO_PHYS.

   3.  Before calling KSEG_TO_PHYS, calls IS_KSEG_VA to determine if the
       virtual address is from the kernel-unmapped address space.

   4.  If the virtual address is from the kernel-unmapped address space, then
       calls KSEG_TO_PHYS to convert the address to a corresponding physical
       address.

SEE ALSO
  Routines: IS_KSEG_VA(9r), PHYS_TO_KSEG(9r)

Index for Section 9r

Alphabetical listing for K

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