Add leap function to servo.

Introduce a new function to inform the servo about upcoming leap second.
This is used when the kernel leap is disabled to allow the servo to
handle better the sudden 1 second step in the offset when the leap
second is inserted or deleted.

Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>

clock.c

@@ -697,6 +697,8 @@ static int clock_utc_correct(struct clock *c, tmv_t ingress)
 		if (c->leap_set != clock_leap) {
 			if (c->kernel_leap)
 				sysclk_set_leap(clock_leap);
+			else
+				servo_leap(c->servo, clock_leap);
 			c->leap_set = clock_leap;
 		}
 	}

phc2sys.c

@@ -1114,6 +1114,8 @@ static int clock_handle_leap(struct node *node, struct clock *clock,
 			if (clock->clkid == CLOCK_REALTIME &&
 			    node->kernel_leap)
 				sysclk_set_leap(clock_leap);
+			else
+				servo_leap(clock->servo, clock_leap);
 			clock->leap_set = clock_leap;
 		}
 	}

servo.c

@@ -107,3 +107,9 @@ double servo_rate_ratio(struct servo *servo)
 
 	return 1.0;
 }
+
+void servo_leap(struct servo *servo, int leap)
+{
+	if (servo->leap)
+		servo->leap(servo, leap);
+}

servo.h

@@ -132,4 +132,12 @@ void servo_reset(struct servo *servo);
  */
 double servo_rate_ratio(struct servo *servo);
 
+/**
+ * Inform a clock servo about upcoming leap second.
+ * @param servo   Pointer to a servo obtained via @ref servo_create().
+ * @param leap    +1 when leap second will be inserted, -1 when leap second
+ *                will be deleted, 0 when it passed.
+ */
+void servo_leap(struct servo *servo, int leap);
+
 #endif

servo_private.h

@@ -38,6 +38,8 @@ struct servo {
 	void (*reset)(struct servo *servo);
 
 	double (*rate_ratio)(struct servo *servo);
+
+	void (*leap)(struct servo *servo, int leap);
 };
 
 #endif