> A brief description of each macro is below.
> 
>         BIT(n): Return a bitmask with bit m 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.

seem like too generic names to me.

YAMAMOTO Takashi