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Silence missing-graph error for DRM bridges

PATCH In review Dmitry Osipenko 3 participants 6 messages Jul 1, 2020

Subsystems (4)
DRM drivers DRM misc Tegra architecture support Device tree
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Dmitry Osipenko

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#0 lore raw

v10 cover Silence missing-graph error for DRM bridges

Hi!

This small series improves DRM bridges code by silencing a noisy error coming from of-graph code for the device-trees that are missing a display bridge graph.

graph: no port node found in ...

One example where this error happens is an older bridge-less DTB used in conjunction with a newer kernel which has a display controller driver that supports DRM bridges.

Changelog:

v10:- Corrected doc-comment, unbroke the of_graph_get_next_endpoint() and
improved commit's message in the "add of_graph_is_present()" patch. Thanks to Laurent Pinchart for spotting the problems!

v9: - These two patches are factored out from [1] in order to ease applying
of the patches.

- The of_graph_presents() is renamed to of_graph_is_present() like it was requested by Rob Herring in the review comment to [1].

- Added Rob's r-b.

[1] https://patchwork.ozlabs.org/project/linux-tegra/list/?series=184102

Dmitry Osipenko (2):
of_graph: add of_graph_is_present()
drm/of: Make drm_of_find_panel_or_bridge() to check graph's presence

 drivers/gpu/drm/drm_of.c |  9 +++++++++
 drivers/of/property.c    | 23 +++++++++++++++++++++++
 include/linux/of_graph.h |  6 ++++++
 3 files changed, 38 insertions(+)
Signature · 1 line
2.26.0
author
#1 lore raw

PATCH v10 1/2 of_graph: add of_graph_is_present()

In some cases it's very useful to silently check whether port node exists at all in a device-tree before proceeding with parsing the graph. The DRM bridges code is one example of such case where absence of a graph in a device-tree is a legit condition.

This patch adds of_graph_is_present() which returns true if given device-tree node contains OF graph port.

Reviewed-by Rob Herring <[email protected]>
Signed-off-by Dmitry Osipenko <[email protected]>
---
 drivers/of/property.c    | 23 +++++++++++++++++++++++
 include/linux/of_graph.h |  6 ++++++
 2 files changed, 29 insertions(+)
drivers/of/property.c +23 -0
index 6a5760f0d6cd..fed7229d9d9f 100644
@@ -29,6 +29,29 @@
 
 #include "of_private.h"
 
+/**
+ * of_graph_is_present() - check graph's presence
+ * @node: pointer to device_node containing graph port
+ *
+ * Return: True if @node has a port or ports (with a port) sub-node,
+ * false otherwise.
+ */
+bool of_graph_is_present(const struct device_node *node)
+{
+	struct device_node *ports, *port;
+
+	ports = of_get_child_by_name(node, "ports");
+	if (ports)
+		node = ports;
+
+	port = of_get_child_by_name(node, "port");
+	of_node_put(ports);
+	of_node_put(port);
+
+	return !!port;
+}
+EXPORT_SYMBOL(of_graph_is_present);
+
 /**
  * of_property_count_elems_of_size - Count the number of elements in a property
  *
include/linux/of_graph.h +6 -0
index 01038a6aade0..4d7756087b6b 100644
@@ -38,6 +38,7 @@ struct of_endpoint {
 	     child = of_graph_get_next_endpoint(parent, child))
 
 #ifdef CONFIG_OF
+bool of_graph_is_present(const struct device_node *node);
 int of_graph_parse_endpoint(const struct device_node *node,
 				struct of_endpoint *endpoint);
 int of_graph_get_endpoint_count(const struct device_node *np);

@@ -56,6 +57,11 @@ struct device_node *of_graph_get_remote_node(const struct device_node *node,
 					     u32 port, u32 endpoint);
 #else
 
+static inline bool of_graph_is_present(const struct device_node *node)
+{
+	return false;
+}
+
 static inline int of_graph_parse_endpoint(const struct device_node *node,
 					struct of_endpoint *endpoint)
 {
Signature · 1 line
2.26.0
Reviewed-by on v10 1/2
#2 lore raw

Re: [PATCH v10 1/2] of_graph: add of_graph_is_present()

Hi Dmitry,

Thank you for the patch.

Quoted 10 lines · Dmitry Osipenko

In some cases it's very useful to silently check whether port node exists at all in a device-tree before proceeding with parsing the graph. The DRM bridges code is one example of such case where absence of a graph in a device-tree is a legit condition.

This patch adds of_graph_is_present() which returns true if given device-tree node contains OF graph port.

Reviewed-by Rob Herring <[email protected]>
Signed-off-by Dmitry Osipenko <[email protected]>
Reviewed-by Laurent Pinchart <laurent.pinchart-ryLnwIuWjnjg/[email protected]>
Quoted 63 lines
---
 drivers/of/property.c    | 23 +++++++++++++++++++++++
 include/linux/of_graph.h |  6 ++++++
 2 files changed, 29 insertions(+)
drivers/of/property.c +23 -0
index 6a5760f0d6cd..fed7229d9d9f 100644
@@ -29,6 +29,29 @@
 
 #include "of_private.h"
 
+/**
+ * of_graph_is_present() - check graph's presence
+ * @node: pointer to device_node containing graph port
+ *
+ * Return: True if @node has a port or ports (with a port) sub-node,
+ * false otherwise.
+ */
+bool of_graph_is_present(const struct device_node *node)
+{
+	struct device_node *ports, *port;
+
+	ports = of_get_child_by_name(node, "ports");
+	if (ports)
+		node = ports;
+
+	port = of_get_child_by_name(node, "port");
+	of_node_put(ports);
+	of_node_put(port);
+
+	return !!port;
+}
+EXPORT_SYMBOL(of_graph_is_present);
+
 /**
  * of_property_count_elems_of_size - Count the number of elements in a property
  *
include/linux/of_graph.h +6 -0
index 01038a6aade0..4d7756087b6b 100644
@@ -38,6 +38,7 @@ struct of_endpoint {
 	     child = of_graph_get_next_endpoint(parent, child))
 
 #ifdef CONFIG_OF
+bool of_graph_is_present(const struct device_node *node);
 int of_graph_parse_endpoint(const struct device_node *node,
 				struct of_endpoint *endpoint);
 int of_graph_get_endpoint_count(const struct device_node *np);

@@ -56,6 +57,11 @@ struct device_node *of_graph_get_remote_node(const struct device_node *node,
 					     u32 port, u32 endpoint);
 #else
 
+static inline bool of_graph_is_present(const struct device_node *node)
+{
+	return false;
+}
+
 static inline int of_graph_parse_endpoint(const struct device_node *node,
 					struct of_endpoint *endpoint)
 {
Signature · 3 lines
Regards,

Laurent Pinchart
author
#3 lore raw

PATCH v10 2/2 drm/of: Make drm_of_find_panel_or_bridge() to check graph's presence

In reply to Dmitry Osipenko

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 <[email protected]>
Signed-off-by Dmitry Osipenko <[email protected]>
---
 drivers/gpu/drm/drm_of.c | 9 +++++++++
 1 file changed, 9 insertions(+)
drivers/gpu/drm/drm_of.c +9 -0
index b50b44e76279..fdb05fbf72a0 100644
@@ -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;
Signature · 1 line
2.26.0
#4 lore raw
In reply to Dmitry Osipenko

Hi Dmitry

Quoted 24 lines · Dmitry Osipenko

Hi!

This small series improves DRM bridges code by silencing a noisy error coming from of-graph code for the device-trees that are missing a display bridge graph.

graph: no port node found in ...

One example where this error happens is an older bridge-less DTB used in conjunction with a newer kernel which has a display controller driver that supports DRM bridges.

Changelog:

v10:- Corrected doc-comment, unbroke the of_graph_get_next_endpoint() and
improved commit's message in the "add of_graph_is_present()" patch. Thanks to Laurent Pinchart for spotting the problems!

v9: - These two patches are factored out from [1] in order to ease applying
of the patches.

- The of_graph_presents() is renamed to of_graph_is_present() like it was requested by Rob Herring in the review comment to [1].

Quoted 7 lines

- Added Rob's r-b.

[1] https://patchwork.ozlabs.org/project/linux-tegra/list/?series=184102

Dmitry Osipenko (2):
of_graph: add of_graph_is_present()
drm/of: Make drm_of_find_panel_or_bridge() to check graph's presence

Thanks for your patience with these - applied to drm-misc-next now.

Sam

Quoted 8 lines
 drivers/gpu/drm/drm_of.c |  9 +++++++++
 drivers/of/property.c    | 23 +++++++++++++++++++++++
 include/linux/of_graph.h |  6 ++++++
 3 files changed, 38 insertions(+)
Signature · 1 line
2.26.0
author
#5 lore raw

01.07.2020 12:02, Sam Ravnborg пишет:

Quoted 28 lines

Hi Dmitry

Quoted 26 lines · Dmitry Osipenko

Hi!

This small series improves DRM bridges code by silencing a noisy error coming from of-graph code for the device-trees that are missing a display bridge graph.

graph: no port node found in ...

One example where this error happens is an older bridge-less DTB used in conjunction with a newer kernel which has a display controller driver that supports DRM bridges.

Changelog:

v10:- Corrected doc-comment, unbroke the of_graph_get_next_endpoint() and
improved commit's message in the "add of_graph_is_present()" patch. Thanks to Laurent Pinchart for spotting the problems!

v9: - These two patches are factored out from [1] in order to ease applying
of the patches.

- The of_graph_presents() is renamed to of_graph_is_present() like it was requested by Rob Herring in the review comment to [1].

- Added Rob's r-b.

Quoted 7 lines
Quoted 5 lines
    [1] https://patchwork.ozlabs.org/project/linux-tegra/list/?series=184102

Dmitry Osipenko (2):
of_graph: add of_graph_is_present()
drm/of: Make drm_of_find_panel_or_bridge() to check graph's presence

Thanks for your patience with these - applied to drm-misc-next now.

Thanks to you and Laurent!