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.

       ddi_btop() 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.

       ddi_btopr() 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.

       ddi_ptob() 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

       ddi_btop() and ddi_btopr() 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 or interrupt 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 5.10							    11 Sep 1991 						      ddi_btop(9F)