kseg_to_phys(9r) osf1 man page | unix.com

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 determine 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 physi-
       cal address.

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

																  KSEG_TO_PHYS(9r)