Refactor the data set comparison function variable.

There is no need to keep two copies of the data set comparison
function.  This patch adds a method that allows the port code to
obtain the function from the clock code.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>

clock.c

@@ -758,6 +758,11 @@ struct config *clock_config(struct clock *c)
 	return c->config;
 }
 
+int (*clock_dscmp(struct clock *c))(struct dataset *a, struct dataset *b)
+{
+	return c->dscmp;
+}
+
 struct currentDS *clock_current_dataset(struct clock *c)
 {
 	return &c->cur;

clock.h

@@ -79,6 +79,13 @@ struct config *clock_config(struct clock *c);
  */
 struct currentDS *clock_current_dataset(struct clock *c);
 
+/**
+ * Obtains the clock's data set comparison function.
+ * @param c  The clock instance.
+ * @return   A pointer to the data set comparison function, without fail.
+ */
+int (*clock_dscmp(struct clock *c))(struct dataset *a, struct dataset *b);
+
 /**
  * Obtains the required time stamping mode.
  * @param c  The clock instance.

port.c

@@ -2191,9 +2191,11 @@ void port_close(struct port *p)
 
 struct foreign_clock *port_compute_best(struct port *p)
 {
+	int (*dscmp)(struct dataset *a, struct dataset *b);
 	struct foreign_clock *fc;
 	struct ptp_message *tmp;
 
+	dscmp = clock_dscmp(p->clock);
 	p->best = NULL;
 
 	LIST_FOREACH(fc, &p->foreign_masters, list) {
@@ -2210,7 +2212,7 @@ struct foreign_clock *port_compute_best(struct port *p)
 
 		if (!p->best)
 			p->best = fc;
-		else if (p->dscmp(&fc->dataset, &p->best->dataset) > 0)
+		else if (dscmp(&fc->dataset, &p->best->dataset) > 0)
 			p->best = fc;
 		else
 			fc_clear(fc);
@@ -2784,7 +2786,6 @@ struct port *port_open(int phc_index,
 	}
 
 	p->state_machine = clock_slave_only(clock) ? ptp_slave_fsm : ptp_fsm;
-	p->dscmp = dscmp;
 	p->phc_index = phc_index;
 	p->jbod = config_get_int(cfg, interface->name, "boundary_clock_jbod");
 	transport = config_get_int(cfg, interface->name, "network_transport");

port_private.h

@@ -88,7 +88,6 @@ struct port {
 	unsigned int multiple_pdr_detected;
 	enum port_state (*state_machine)(enum port_state state,
 					 enum fsm_event event, int mdiff);
-	int (*dscmp)(struct dataset *a, struct dataset *b);
 	/* portDS */
 	struct PortIdentity portIdentity;
 	enum port_state     state; /*portState*/