rounddown_pow_of_2 inclusion into log2.h

Quoted 5 lines · vignesh babu

rday,

Any plans on including what Andrew Morton suggested in the near
future? Think you have had enough time to convince yourself ;)

if there's value in it, the following seems to work fine in terms of
rounding down to the nearest power of two.

static inline unsigned long
rounddown_pow_of_two(unsigned long n)

{
	return (n = 1) ? 0 : (1UL << ilog2(n));
}

args that are already a power of two will be unchanged, 1 will
clearly return 0, but an arg of zero should also be caught since that's undefined -- perhaps it should also return zero?

in any event, that routine seems to work fine. are there enough
places in the source tree to make this cleanup worth it?

rday