phc2sys: enable PPS output from PHC

PPS output from a PHC has to be enabled by PTP_ENABLE_PPS ioctl. Call
the ioctl when both PHC device and PPS device are specified and PPS is
supported by the PHC.

Signed-off-by: Jiri Benc <jbenc@redhat.com>

phc.c

@@ -51,15 +51,23 @@ void phc_close(clockid_t clkid)
 	close(CLOCKID_TO_FD(clkid));
 }
 
+static int phc_get_caps(clockid_t clkid, struct ptp_clock_caps *caps)
+{
+	int fd = CLOCKID_TO_FD(clkid), err;
+
+	err = ioctl(fd, PTP_CLOCK_GETCAPS, caps);
+	if (err)
+		perror("PTP_CLOCK_GETCAPS");
+	return err;
+}
+
 int phc_max_adj(clockid_t clkid)
 {
-	int fd = CLOCKID_TO_FD(clkid), max;
+	int max;
 	struct ptp_clock_caps caps;
 
-	if (ioctl(fd, PTP_CLOCK_GETCAPS, &caps)) {
+	if (phc_get_caps(clkid, &caps))
-		perror("PTP_CLOCK_GETCAPS");
 		return 0;
-	}
 
 	max = caps.max_adj;
 
@@ -68,3 +76,12 @@ int phc_max_adj(clockid_t clkid)
 
 	return max;
 }
+
+int phc_has_pps(clockid_t clkid)
+{
+	struct ptp_clock_caps caps;
+
+	if (phc_get_caps(clkid, &caps))
+		return 0;
+	return caps.pps;
+}

phc.h

@@ -46,4 +46,14 @@ void phc_close(clockid_t clkid);
  */
 int phc_max_adj(clockid_t clkid);
 
+/**
+ * Checks whether the given PTP hardware clock device supports PPS output.
+ *
+ * @param clkid A clock ID obtained using phc_open().
+ *
+ * @return Zero if PPS output is not supported by the clock, non-zero
+ * otherwise.
+ */
+int phc_has_pps(clockid_t clkid);
+
 #endif

phc2sys.c

@@ -206,6 +206,16 @@ static void update_clock(struct clock *clock,
 	}
 }
 
+static void enable_pps_output(clockid_t src)
+{
+	int enable = 1;
+
+	if (!phc_has_pps(src))
+		return;
+	if (ioctl(CLOCKID_TO_FD(src), PTP_ENABLE_PPS, enable) < 0)
+		pr_warning("failed to enable PPS output");
+}
+
 static int read_pps(int fd, int64_t *offset, uint64_t *ts)
 {
 	struct pps_fdata pfd;
@@ -236,9 +246,12 @@ static int do_pps_loop(struct clock *clock, int fd,
 
 	clock->source_label = "pps";
 
+	if (src == CLOCK_INVALID) {
 		/* The sync offset can't be applied with PPS alone. */
-	if (src == CLOCK_INVALID)
 		clock->sync_offset_direction = 0;
+	} else {
+		enable_pps_output(src);
+	}
 
 	while (1) {
 		if (!read_pps(fd, &pps_offset, &pps_ts)) {