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_next_port_on_path().

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Reviewed-by: Lukas Wunner <lukas@wunner.de>

diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
index 6f98b3d6eb2a05713ec648ab19cb106966a78456..ecd41f7b764964abb1455b60d13d04b14682174e 100644 (file)
--- a/drivers/thunderbolt/switch.c
+++ b/drivers/thunderbolt/switch.c
@@ -676,6 +676,60 @@ void tb_port_release_out_hopid(struct tb_port *port, int hopid)
        ida_simple_remove(&port->out_hopids, hopid);
 }
 
+/**
+ * tb_next_port_on_path() - Return next port for given port on a path
+ * @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 @end port has been reached, return %NULL.
+ *
+ * Domain tb->lock must be held when this function is called.
+ */
+struct tb_port *tb_next_port_on_path(struct tb_port *start, struct tb_port *end,
+                                    struct tb_port *prev)
+{
+       struct tb_port *next;
+
+       if (!prev)
+               return start;
+
+       if (prev->sw == end->sw) {
+               if (prev == end)
+                       return NULL;
+               return end;
+       }
+
+       if (start->sw->config.depth < end->sw->config.depth) {
+               if (prev->remote &&
+                   prev->remote->sw->config.depth > prev->sw->config.depth)
+                       next = prev->remote;
+               else
+                       next = tb_port_at(tb_route(end->sw), prev->sw);
+       } else {
+               if (tb_is_upstream_port(prev)) {
+                       next = prev->remote;
+               } else {
+                       next = tb_upstream_port(prev->sw);
+                       /*
+                        * Keep the same link if prev and next are both
+                        * dual link ports.
+                        */
+                       if (next->dual_link_port &&
+                           next->link_nr != prev->link_nr) {
+                               next = 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 43bc4f4900213d25d56c49dd5e1d2845ebb1458e..11d5ab53ad36b39d29c4fae0b401aa687f07a021 100644 (file)
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -495,6 +495,8 @@ 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_next_port_on_path(struct tb_port *start, struct tb_port *end,
+                                    struct tb_port *prev);
 
 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);