[RFC/PATCH 2/3] of: add of_lookup_stdout() utility function

[Grant Likely]

From: Grant Likely <grant.likely at secretlab.ca>

of_lookup_stdout() is useful for figuring out what device to use as output
for early boot progress messages.  It returns the node pointed to by the
linux,stdout-path property in the chosen node.

Signed-off-by: Grant Likely <grant.likely at secretlab.ca>
---

 drivers/of/base.c  |   24 ++++++++++++++++++++++++
 include/linux/of.h |    1 +
 2 files changed, 25 insertions(+), 0 deletions(-)

diff --git a/drivers/of/base.c b/drivers/of/base.c
index ad8ac1a..10c6a46 100644
--- a/drivers/of/base.c
+++ b/drivers/of/base.c
@@ -473,3 +473,27 @@ int of_modalias_node(struct device_node *node, char *modalias, int len)
 }
 EXPORT_SYMBOL_GPL(of_modalias_node);
 
+/**
+ * of_lookup_stdout - find node pointed to by chosen linux,stdout-path property
+ *
+ * This routine returns a pointer to the stdout node or NULL on failure
+ */
+struct device_node __init *of_lookup_stdout(void)
+{
+	struct device_node *chosen, *stdout_node;
+	const char *stdout_path;
+
+	chosen = of_find_node_by_path("/chosen");
+	if (!chosen)
+		return NULL;
+
+	stdout_path = of_get_property(chosen, "linux,stdout-path", NULL);
+	if (!stdout_path) {
+		of_node_put(chosen);
+		return NULL;
+	}
+
+	stdout_node = of_find_node_by_path(stdout_path);
+	of_node_put(chosen);
+	return stdout_node;
+}
diff --git a/include/linux/of.h b/include/linux/of.h
index 79886ad..e8b215b 100644
--- a/include/linux/of.h
+++ b/include/linux/of.h
@@ -71,5 +71,6 @@ extern int of_n_size_cells(struct device_node *np);
 extern const struct of_device_id *of_match_node(
 	const struct of_device_id *matches, const struct device_node *node);
 extern int of_modalias_node(struct device_node *node, char *modalias, int len);
+struct device_node __init *of_lookup_stdout(void);
 
 #endif /* _LINUX_OF_H */