man/man9f/ddi_btop.9f

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 DDI_BTOP 9F "Jan 16, 2006"
 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