KSEG_TO_PHYS man page on DigitalUNIX

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KSEG_TO_PHYS(9r)					      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
       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]

       .  .  .

       Declares a  variable  to	 store	the  user  buffer's  virtual  address.
       Declares	  a  variable  to  store  the  physical	 address  returned  by
       KSEG_TO_PHYS.  Before calling KSEG_TO_PHYS, calls IS_KSEG_VA to	deterÔÇÉ
       mine  if the virtual address is from the kernel-unmapped address space.
       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)

							      KSEG_TO_PHYS(9r)
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