[PATCH v10 0/2] Silence missing-graph error for DRM bridges

[PATCH v10 0/2] Silence missing-graph error for DRM bridges

[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.

    [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(+)

-- 
2.26.0

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

[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 <robh@kernel.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
---
 drivers/of/property.c    | 23 +++++++++++++++++++++++
 include/linux/of_graph.h |  6 ++++++
 2 files changed, 29 insertions(+)

diff --git a/drivers/of/property.c b/drivers/of/property.c
index 6a5760f0d6cd..fed7229d9d9f 100644
--- a/drivers/of/property.c
+++ b/drivers/of/property.c
@@ -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
  *
diff --git a/include/linux/of_graph.h b/include/linux/of_graph.h
index 01038a6aade0..4d7756087b6b 100644
--- a/include/linux/of_graph.h
+++ b/include/linux/of_graph.h
@@ -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)
 {
-- 
2.26.0

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

[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 <sam@ravnborg.org>
Signed-off-by: Dmitry Osipenko <digetx@gmail.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

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

[Laurent Pinchart]

Hi Dmitry,

Thank you for the patch.

On Wed, Jul 01, 2020 at 10:42:31AM +0300, Dmitry Osipenko wrote:
> 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 <robh@kernel.org>
> Signed-off-by: Dmitry Osipenko <digetx@gmail.com>

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

> ---
>  drivers/of/property.c    | 23 +++++++++++++++++++++++
>  include/linux/of_graph.h |  6 ++++++
>  2 files changed, 29 insertions(+)
> 
> diff --git a/drivers/of/property.c b/drivers/of/property.c
> index 6a5760f0d6cd..fed7229d9d9f 100644
> --- a/drivers/of/property.c
> +++ b/drivers/of/property.c
> @@ -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
>   *
> diff --git a/include/linux/of_graph.h b/include/linux/of_graph.h
> index 01038a6aade0..4d7756087b6b 100644
> --- a/include/linux/of_graph.h
> +++ b/include/linux/of_graph.h
> @@ -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)
>  {

-- 
Regards,

Laurent Pinchart

Re: [PATCH v10 0/2] Silence missing-graph error for DRM bridges

[Sam Ravnborg]

Hi Dmitry
On Wed, Jul 01, 2020 at 10:42:30AM +0300, Dmitry Osipenko wrote:
> 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

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

	Sam

> 
>  drivers/gpu/drm/drm_of.c |  9 +++++++++
>  drivers/of/property.c    | 23 +++++++++++++++++++++++
>  include/linux/of_graph.h |  6 ++++++
>  3 files changed, 38 insertions(+)
> 
> -- 
> 2.26.0

Re: [PATCH v10 0/2] Silence missing-graph error for DRM bridges

[Dmitry Osipenko]

01.07.2020 12:02, Sam Ravnborg пишет:
> Hi Dmitry
> On Wed, Jul 01, 2020 at 10:42:30AM +0300, Dmitry Osipenko wrote:
>> 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
> 
> Thanks for your patience with these - applied to drm-misc-next now.

Thanks to you and Laurent!