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

illumos DDI specific (illumos 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
corresponding 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

January 16, 2006 DDI_BTOP(9F)