Name
ffs — 
     find first set bit in word
 
Description
   This is defined the same way as the libc and compiler builtin ffs
   routines, therefore differs in spirit from the other bitops.
   
   ffs(value) returns 0 if value is 0 or the position of the first
   set bit if value is nonzero. The first (least significant) bit
   is at position 1.