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

NAME

ddi_ffs, ddi_fls - find first (last) bit set in a long integer

SYNOPSIS

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


int ddi_ffs(long mask);


int ddi_fls(long mask);

INTERFACE LEVEL

illumos DDI specific (illumos DDI).

PARAMETERS

mask
A 64-bit argument value to search through.

DESCRIPTION

The function ddi_ffs() takes its argument and returns the shift count
that the first (least significant) bit set in the argument
corresponds to. The function ddi_fls() does the same, only it returns
the shift count for the last (most significant) bit set in the
argument.

RETURN VALUES

0
No bits are set in mask.


N
Bit N is the least significant (ddi_ffs) or most significant
(ddi_fls) bit set in mask. Bits are numbered from 1 to 64, with
bit 1 being the least significant bit position and bit 64 the
most significant position.

CONTEXT

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

SEE ALSO

Writing Device Drivers

January 16, 2021 DDI_FFS(9F)