Why do we need to specify hrtimer_mode twice while using hrtimers.

1. Timer Initialization:

   void hrtimer_init(struct hrtimer *timer, clockid_t which_clock, enum hrtimer_mode mode);

2. Starting a timer:

   void hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode);

What will happen if i specify different modes in both functions.