linux-kernel - [PATCH v2 13/28] thunderbolt: Add helper function to iterate from one port to another

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Date:   Wed,  6 Feb 2019 16:17:23 +0300
From:   Mika Westerberg <mika.westerberg@...ux.intel.com>
To:     linux-kernel@...r.kernel.org
Cc:     Michael Jamet <michael.jamet@...el.com>,
        Yehezkel Bernat <YehezkelShB@...il.com>,
        Andreas Noever <andreas.noever@...il.com>,
        Lukas Wunner <lukas@...ner.de>,
        "David S . Miller" <davem@...emloft.net>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        netdev@...r.kernel.org
Subject: [PATCH v2 13/28] thunderbolt: Add helper function to iterate from one port to another

We need to be able to walk from one port to another when we are creating
paths where there are multiple switches between two ports. For this
reason introduce a new function tb_port_get_next() and a new macro
tb_for_each_port().

Signed-off-by: Mika Westerberg <mika.westerberg@...ux.intel.com>
---
 drivers/thunderbolt/switch.c | 60 ++++++++++++++++++++++++++++++++++++
 drivers/thunderbolt/tb.h     |  6 ++++
 2 files changed, 66 insertions(+)

diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
index 320f64ebe8b8..23b6bae8362e 100644
--- a/drivers/thunderbolt/switch.c
+++ b/drivers/thunderbolt/switch.c
@@ -683,6 +683,66 @@ void tb_port_release_out_hopid(struct tb_port *port, int hopid)
 	ida_simple_remove(&port->out_hopids, hopid);
 }
 
+/**
+ * tb_port_get_next() - Return next port for given port
+ * @start: Start port of the walk
+ * @end: End port of the walk
+ * @prev: Previous port (%NULL if this is the first)
+ *
+ * This function can be used to walk from one port to another if they
+ * are connected through zero or more switches. If the @prev is dual
+ * link port, the function follows that link and returns another end on
+ * that same link.
+ *
+ * If the walk cannot be continued, returns %NULL.
+ *
+ * Domain tb->lock must be held when this function is called.
+ */
+struct tb_port *tb_port_get_next(struct tb_port *start, struct tb_port *end,
+				 struct tb_port *prev)
+{
+	struct tb_port *port, *next;
+
+	if (!prev)
+		return start;
+
+	if (prev->sw == end->sw) {
+		if (prev != end)
+			return end;
+		return NULL;
+	}
+
+	/* Switch back to use primary links for walking */
+	if (prev->dual_link_port && prev->link_nr)
+		port = prev->dual_link_port;
+	else
+		port = prev;
+
+	if (start->sw->config.depth < end->sw->config.depth) {
+		if (port->remote &&
+		    port->remote->sw->config.depth > port->sw->config.depth)
+			next = port->remote;
+		else
+			next = tb_port_at(tb_route(end->sw), port->sw);
+	} else if (start->sw->config.depth > end->sw->config.depth) {
+		if (tb_is_upstream_port(port))
+			next = port->remote;
+		else
+			next = tb_upstream_port(port->sw);
+	} else {
+		/* Must be the same switch then */
+		if (start->sw != end->sw)
+			return NULL;
+		return end;
+	}
+
+	/* If prev was dual link return another end of that link then */
+	if (next->dual_link_port && next->link_nr != prev->link_nr)
+		return next->dual_link_port;
+
+	return next;
+}
+
 /**
  * tb_pci_port_enable() - Enable PCIe adapter port
  * @port: PCIe port to enable
diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index bfa1cee193fd..683725915ff7 100644
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -447,6 +447,12 @@ int tb_port_alloc_in_hopid(struct tb_port *port, int hopid, int max_hopid);
 void tb_port_release_in_hopid(struct tb_port *port, int hopid);
 int tb_port_alloc_out_hopid(struct tb_port *port, int hopid, int max_hopid);
 void tb_port_release_out_hopid(struct tb_port *port, int hopid);
+struct tb_port *tb_port_get_next(struct tb_port *start, struct tb_port *end,
+				 struct tb_port *prev);
+
+#define tb_for_each_port(port, start, end)			\
+	for (port = tb_port_get_next(start, end, NULL); port;	\
+	     port = tb_port_get_next(start, end, port))
 
 int tb_switch_find_vse_cap(struct tb_switch *sw, enum tb_switch_vse_cap vsec);
 int tb_port_find_cap(struct tb_port *port, enum tb_port_cap cap);
-- 
2.20.1