thunderbolt: Introduce tb_switch_downstream_port()

Introduce tb_switch_downstream_port() helper function that returns the
downstream port of a parent switch that is connected to the upstream
port of specified switch. From now on, we use it all across the driver
where applicable.

While there fix a whitespace in comment and rename 'downstream' to
'down' to be consistent with the rest of the driver.

Signed-off-by: Gil Fine <gil.fine@intel.com>
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index 275ff5219a3a..a8e1725b4cb5 100644
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -857,6 +857,20 @@ static inline struct tb_switch *tb_switch_parent(struct tb_switch *sw)
 	return tb_to_switch(sw->dev.parent);
 }
 
+/**
+ * tb_switch_downstream_port() - Return downstream facing port of parent router
+ * @sw: Device router pointer
+ *
+ * Only call for device routers. Returns the downstream facing port of
+ * the parent router.
+ */
+static inline struct tb_port *tb_switch_downstream_port(struct tb_switch *sw)
+{
+	if (WARN_ON(!tb_route(sw)))
+		return NULL;
+	return tb_port_at(tb_route(sw), tb_switch_parent(sw));
+}
+
 static inline bool tb_switch_is_light_ridge(const struct tb_switch *sw)
 {
 	return sw->config.vendor_id == PCI_VENDOR_ID_INTEL &&