ddi_ffs(9f) [opensolaris man page]

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>

       intddi_ffs(long mask);

       int ddi_fls(long mask);

INTERFACE LEVEL

       Solaris DDI specific (Solaris DDI).

PARAMETERS

       mask    A 32-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 corre-
       sponds 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  32, with bit 1
	    being the least significant bit position and bit 32 the most significant position.

CONTEXT

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

SEE ALSO

       Writing Device Drivers

SunOS 5.11							    16 Jan 2006 						       ddi_ffs(9F)

BITS(3) 						   BSD Library Functions Manual 						   BITS(3)

NAME

     __BIT, __BITS, __SHIFTIN, __SHIFTOUT, __SHIFTOUT_MASK -- macros for preparing bitmasks and operating on bit fields

SYNOPSIS

     #include <sys/param.h>
     #include <sys/cdefs.h>

     uintmax_t
     __BIT(n);

     uintmax_t
     __BITS(m, n);

     __SHIFTIN(v, mask);

     __SHIFTOUT(v, mask);

     __SHIFTOUT_MASK(mask);

DESCRIPTION

     These macros prepare bitmasks, extract bitfields from words, and insert bitfields into words.  A ``bitfield'' is a span of consecutive bits
     defined by a bitmask, where 1s select the bits in the bitfield.

     Use __BIT() and __BITS() to define bitmasks:

	   __BIT(n)
		   Return a bitmask with bit n set, where the least significant bit is bit 0.

	   __BITS(m, n)
		   Return a bitmask with bits m through n, inclusive, set.  It does not matter whether m > n or m <= n.  The least significant bit
		   is bit 0.

     __SHIFTIN(), __SHIFTOUT(), and __SHIFTOUT_MASK() help read and write bitfields from words:

	   __SHIFTIN(v, mask)
			    Left-shift bits v into the bitfield defined by mask, and return them.  No side-effects.

	   __SHIFTOUT(v, mask)
			    Extract and return the bitfield selected by mask from v, right-shifting the bits so that the rightmost selected bit is
			    at bit 0.  No side-effects.

	   __SHIFTOUT_MASK(mask)
			    Right-shift the bits in mask so that the rightmost non-zero bit is at bit 0.  This is useful for finding the greatest
			    unsigned value that a bitfield can hold.  No side-effects.	Note that __SHIFTOUT_MASK(m) = __SHIFTOUT(m, m).

EXAMPLES

     The following example demonstrates basic usage of the bits macros:

	   uint32_t bits, mask, val;

	   bits = __BITS(2, 3); 		   /* 00001100 */
	   mask = __BIT(2) | __BIT(3);		   /* 00001100 */

	   val = __SHIFTIN(0x03, mask); 	   /* 00001100 */
	   val = __SHIFTOUT(0xf, mask); 	   /* 00000011 */

SEE ALSO

     bitops(3), cdefs(3)

HISTORY

     The bits macros first appeared in atw(4), with different names and implementation.  In their current form these macros appeared in
     NetBSD 4.0.

AUTHORS

     The bits macros were written by David Young <dyoung@NetBSD.org>.
     Matt Thomas <matt@NetBSD.org> suggested important improvements to the implementation, and contributed the macro names SHIFTIN() and
     SHIFTOUT().

BUGS

     __BIT() and __BITS() can only express 32-bit bitmasks.

BSD
								 October 17, 2012							       BSD