opensolaris man page for ddi_btop

ddi_btop(9F)						   Kernel Functions for Drivers 					      ddi_btop(9F)

NAME
       ddi_btop, ddi_btopr, ddi_ptob - page size conversions

SYNOPSIS
       #include <sys/ddi.h>
       #include <sys/sunddi.h>

       unsigned long ddi_btop(dev_info_t *dip, unsigned long bytes);

       unsigned long ddi_btopr(dev_info_t *dip, unsigned long bytes);

       unsigned long ddi_ptob(dev_info_t *dip, unsigned long pages);

INTERFACE LEVEL
       Solaris DDI specific (Solaris DDI).

DESCRIPTION
       This set of routines use the parent nexus driver to perform conversions in page size units.

       The  ddi_btop() function converts the given number of bytes to the number of memory pages that it corresponds to, rounding down in the case
       that the byte count is not a page multiple.

       The ddi_btopr() function converts the given number of bytes to the number of memory pages that it corresponds to, rounding up in  the  case
       that the byte count is not a page multiple.

       The ddi_ptob() function converts the given number of pages to the number of bytes that it corresponds to.

       Because	bus nexus may possess their own hardware address translation facilities, these routines should be used in preference to the corre-
       sponding DDI/DKI routines btop(9F), btopr(9F), and ptob(9F), which only deal in terms of the pagesize of the main system MMU.

RETURN VALUES
       The ddi_btop() and ddi_btopr() functions return the number of corresponding pages. ddi_ptob() returns the corresponding	number	of  bytes.
       There are no error return values.

CONTEXT
       This function can be called from user, interrupt, or kernel context.

EXAMPLES
       Example 1 Find the size (in bytes) of one page

	 pagesize = ddi_ptob(dip, 1L);

SEE ALSO
       btop(9F), btopr(9F), ptob(9F)

       Writing Device Drivers

SunOS 5.11							    16 Jan 2006 						      ddi_btop(9F)