linux-kernel - [PATCH v10 2/2] drm/of: Make drm_of_find_panel_or

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Date:   Wed,  1 Jul 2020 10:42:32 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Sam Ravnborg <sam@...nborg.org>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>
Cc:     dri-devel@...ts.freedesktop.org, linux-tegra@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH v10 2/2] 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@...nborg.org>
Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 drivers/gpu/drm/drm_of.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/gpu/drm/drm_of.c b/drivers/gpu/drm/drm_of.c
index b50b44e76279..fdb05fbf72a0 100644
--- 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;
-- 
2.26.0