From f8563452a82b0690a838b493719eb99f559d1c3f Mon Sep 17 00:00:00 2001
From: Miroslav Lichvar <mlichvar@redhat.com>
Date: Thu, 4 Apr 2013 17:28:23 +0200
Subject: [PATCH] ptp4l: Read system clock maximum frequency adjustment.

Signed-off-by: Miroslav Lichvar <mlichvar@redhat.com>
---
 clock.c    |  2 +-
 clockadj.c | 14 ++++++++++++++
 clockadj.h |  7 +++++++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/clock.c b/clock.c
index 44ef81a..e4af8f4 100644
--- a/clock.c
+++ b/clock.c
@@ -589,7 +589,7 @@ struct clock *clock_create(int phc_index, struct interface *iface, int count,
 	} else {
 		c->clkid = CLOCK_REALTIME;
 		c->utc_timescale = 1;
-		max_adj = 512000;
+		max_adj = clockadj_get_max_freq(c->clkid);
 		clockadj_set_leap(c->clkid, 0);
 	}
 	c->leap_set = 0;
diff --git a/clockadj.c b/clockadj.c
index 31fc765..7587dda 100644
--- a/clockadj.c
+++ b/clockadj.c
@@ -94,3 +94,17 @@ void clockadj_set_leap(clockid_t clkid, int leap)
 	else if (m)
 		pr_notice(m);
 }
+
+int clockadj_get_max_freq(clockid_t clkid)
+{
+	int f = 0;
+	struct timex tx;
+	memset(&tx, 0, sizeof(tx));
+	if (clock_adjtime(clkid, &tx) < 0)
+		pr_err("failed to read out the clock maximum adjustment: %m");
+	else
+		f = tx.tolerance / 65.536;
+	if (!f)
+		f = 500000;
+	return f;
+}
diff --git a/clockadj.h b/clockadj.h
index 6e76e0f..dc94cfa 100644
--- a/clockadj.h
+++ b/clockadj.h
@@ -51,4 +51,11 @@ void clockadj_step(clockid_t clkid, int64_t step);
  *              0 to reset the leap state.
  */
 void clockadj_set_leap(clockid_t clkid, int leap);
+
+/*
+ * Read clock's maximum frequency adjustment.
+ * @param clkid CLOCK_REALTIME.
+ * @return      The maximum frequency adjustment in parts per billion (ppb).
+ */
+int clockadj_get_max_freq(clockid_t clkid);
 #endif