From c7fb52572179b4009cd7dcb7e0a841af3808a7d2 Mon Sep 17 00:00:00 2001
From: Richard Cochran <richardcochran@gmail.com>
Date: Tue, 14 Feb 2017 19:55:51 +0100
Subject: [PATCH] telecom: Add a configuration option for
 G.8275.defaultDS.localPriority.

Signed-off-by: Richard Cochran <richardcochran@gmail.com>
---
 clock.c     |  3 ++-
 config.c    |  1 +
 default.cfg |  1 +
 gPTP.cfg    |  1 +
 ptp4l.8     | 14 ++++++++++++++
 5 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/clock.c b/clock.c
index 19ce805..90f5b0f 100644
--- a/clock.c
+++ b/clock.c
@@ -931,7 +931,8 @@ struct clock *clock_create(enum clock_type type, struct config *config,
 	    c->dds.flags & DDS_SLAVE_ONLY) {
 		c->dds.clockQuality.clockClass = 255;
 	}
-	c->default_dataset.localPriority = 128;
+	c->default_dataset.localPriority =
+		config_get_int(config, NULL, "G.8275.defaultDS.localPriority");
 
 	/* Harmonize the twoStepFlag with the time_stamping option. */
 	if (config_harmonize_onestep(config)) {
diff --git a/config.c b/config.c
index 320cc1b..9c26ccd 100644
--- a/config.c
+++ b/config.c
@@ -192,6 +192,7 @@ struct config_item config_tab[] = {
 	PORT_ITEM_INT("follow_up_info", 0, 0, 1),
 	GLOB_ITEM_INT("free_running", 0, 0, 1),
 	PORT_ITEM_INT("freq_est_interval", 1, 0, INT_MAX),
+	GLOB_ITEM_INT("G.8275.defaultDS.localPriority", 128, 1, UINT8_MAX),
 	GLOB_ITEM_INT("gmCapable", 1, 0, 1),
 	PORT_ITEM_INT("hybrid_e2e", 0, 0, 1),
 	PORT_ITEM_INT("ignore_transport_specific", 0, 0, 1),
diff --git a/default.cfg b/default.cfg
index e76aeae..9736568 100644
--- a/default.cfg
+++ b/default.cfg
@@ -15,6 +15,7 @@ free_running		0
 freq_est_interval	1
 dscp_event		0
 dscp_general		0
+G.8275.defaultDS.localPriority	128
 #
 # Port Data Set
 #
diff --git a/gPTP.cfg b/gPTP.cfg
index 1e7a33e..02fd395 100644
--- a/gPTP.cfg
+++ b/gPTP.cfg
@@ -13,6 +13,7 @@ clockAccuracy		0xFE
 offsetScaledLogVariance	0xFFFF
 free_running		0
 freq_est_interval	1
+G.8275.defaultDS.localPriority	128
 #
 # Port Data Set
 #
diff --git a/ptp4l.8 b/ptp4l.8
index 950e07c..10f55f2 100644
--- a/ptp4l.8
+++ b/ptp4l.8
@@ -341,6 +341,20 @@ The offsetScaledLogVariance attribute of the local clock. It characterizes the
 stability of the clock.
 The default is 0xFFFF.
 .TP
+.B G.8275.defaultDS.localPriority
+The Telecom Profiles (ITU-T G.8275.1 and G.8275.2) specify an
+alternate Best Master Clock Algorithm (BMCA) with a unique data set
+comparison algorithm.  The value of this option is associated with the
+local clock and is used as a tie breaker whenever clockClass,
+clockAccuracy, offsetScaledLogVariance, and priority2 are equal. This
+option is only used when "dataset_comparison" is set to "telecom".
+The default value is 128.
+
+Warning: the BMCA is guaranteed to produce a spanning tree (that is, a
+timing network without loops) only when using the default values of
+G.8275.defaultDS.localPriority and G.8275.portDS.localPriority.
+Careful network engineering is needed when using non-default values.
+.TP
 .B domainNumber
 The domain attribute of the local clock.
 The default is 0.