drm/of: Make drm_of_find_panel_or_bridge() to check graph's presence

When graph isn't defined in a device-tree, the of_graph_get_remote_node()
prints a noisy error message, telling that port node is not found. This is
undesirable behaviour in our case because absence of a panel/bridge graph
is a valid case. Let's check the graph's presence in a device-tree before
proceeding with parsing of the graph.

Reviewed-by: Sam Ravnborg <sam@ravnborg.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20200701074232.13632-3-digetx@gmail.com

diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
index b50b44e..fdb05fb 100644 (file)
--- a/drivers/gpu/drm/drm_of.c
+++ b/drivers/gpu/drm/drm_of.c
@@ -246,6 +246,15 @@ int drm_of_find_panel_or_bridge(const struct device_node *np,
        if (panel)
                *panel = NULL;
 
+       /*
+        * of_graph_get_remote_node() produces a noisy error message if port
+        * node isn't found and the absence of the port is a legit case here,
+        * so at first we silently check whether graph presents in the
+        * device-tree node.
+        */
+       if (!of_graph_is_present(np))
+               return -ENODEV;
+
        remote = of_graph_get_remote_node(np, port, endpoint);
        if (!remote)
                return -ENODEV;