ns_to_ktime
timeout = ktime_sub(ns_to_ktime(timeout_ns), ktime_get());
abs_timeout = ns_to_ktime(timeout_nsec);
ns_to_ktime(POLL_PERIOD),
hrtimer_forward_now(hrtimer, ns_to_ktime(POLL_PERIOD));
ns_to_ktime(PERIOD), 0,
hrtimer_forward(hrtimer, now, ns_to_ktime(PERIOD));