ptp: remember the adjusted frequency

This patch adds a field to the representation of a PTP hardware clock in
order to remember the frequency adjustment value dialed by the user.

Adding this field will let us answer queries in the manner of adjtimex
in a follow on patch.
Signed-off-by: Richard Cochran <richardcochran@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/ptp/ptp_clock.c

@@ -147,6 +147,7 @@ static int ptp_clock_adjtime(struct posix_clock *pc, struct timex *tx)
 	} else if (tx->modes & ADJ_FREQUENCY) {
 
 		err = ops->adjfreq(ops, scaled_ppm_to_ppb(tx->freq));
+		ptp->dialed_frequency = tx->freq;
 	}
 
 	return err;

drivers/ptp/ptp_private.h

@@ -45,6 +45,7 @@ struct ptp_clock {
 	dev_t devid;
 	int index; /* index into clocks.map */
 	struct pps_device *pps_source;
+	long dialed_frequency; /* remembers the frequency adjustment */
 	struct timestamp_event_queue tsevq; /* simple fifo for time stamps */
 	struct mutex tsevq_mux; /* one process at a time reading the fifo */
 	wait_queue_head_t tsev_wq;