1 files changed, 80 insertions, 0 deletions
diff --git a/drivers/hwtracing/coresight/coresight-sysfs.c b/drivers/hwtracing/coresight/coresight-sysfs.c
index 6759f78733ab..82afeaf2ccc4 100644
--- a/drivers/hwtracing/coresight/coresight-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-sysfs.c
@@ -122,3 +122,83 @@ void coresight_remove_sysfs_link(struct coresight_sysfs_link *info)
 	info->orig->nr_links--;
 	info->target->nr_links--;
 }
+
+/*
+ * coresight_make_links: Make a link for a connection from a @orig
+ * device to @target, represented by @conn.
+ *
+ *   e.g, for devOrig[output_X] -> devTarget[input_Y] is represented
+ *   as two symbolic links :
+ *
+ *	/sys/.../devOrig/out:X	-> /sys/.../devTarget/
+ *	/sys/.../devTarget/in:Y	-> /sys/.../devOrig/
+ *
+ * The link names are allocated for a device where it appears. i.e, the
+ * "out" link on the master and "in" link on the slave device.
+ * The link info is stored in the connection record for avoiding
+ * the reconstruction of names for removal.
+ */
+int coresight_make_links(struct coresight_device *orig,
+			 struct coresight_connection *conn,
+			 struct coresight_device *target)
+{
+	int ret = -ENOMEM;
+	char *outs = NULL, *ins = NULL;
+	struct coresight_sysfs_link *link = NULL;
+
+	do {
+		outs = devm_kasprintf(&orig->dev, GFP_KERNEL,
+				      "out:%d", conn->outport);
+		if (!outs)
+			break;
+		ins = devm_kasprintf(&target->dev, GFP_KERNEL,
+				     "in:%d", conn->child_port);
+		if (!ins)
+			break;
+		link = devm_kzalloc(&orig->dev,
+				    sizeof(struct coresight_sysfs_link),
+				    GFP_KERNEL);
+		if (!link)
+			break;
+
+		link->orig = orig;
+		link->target = target;
+		link->orig_name = outs;
+		link->target_name = ins;
+
+		ret = coresight_add_sysfs_link(link);
+		if (ret)
+			break;
+
+		conn->link = link;
+
+		/*
+		 * Install the device connection. This also indicates that
+		 * the links are operational on both ends.
+		 */
+		conn->child_dev = target;
+		return 0;
+	} while (0);
+
+	return ret;
+}
+
+/*
+ * coresight_remove_links: Remove the sysfs links for a given connection @conn,
+ * from @orig device to @target device. See coresight_make_links() for more
+ * details.
+ */
+void coresight_remove_links(struct coresight_device *orig,
+			    struct coresight_connection *conn)
+{
+	if (!orig || !conn->link)
+		return;
+
+	coresight_remove_sysfs_link(conn->link);
+
+	devm_kfree(&conn->child_dev->dev, conn->link->target_name);
+	devm_kfree(&orig->dev, conn->link->orig_name);
+	devm_kfree(&orig->dev, conn->link);
+	conn->link = NULL;
+	conn->child_dev = NULL;
+}