[PATCH 1/3] serial_core: Add helper for matching against linux,stdout-path

[Sascha Hauer]

devicetrees may have a linux,stdout-path property in the chosen
node describing the console device. This adds a helper function
to match a device against this property so a driver can call
add_preferred_console for a matching device.

Signed-off-by: Sascha Hauer <s.hauer@xxxxxxxxxxxxxx>
---
 drivers/tty/serial/serial_core.c |   30 ++++++++++++++++++++++++++++++
 include/linux/serial_core.h      |    3 +++
 2 files changed, 33 insertions(+)

diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index a21dc8e..f4a9f26 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -33,6 +33,7 @@
 #include <linux/serial_core.h>
 #include <linux/delay.h>
 #include <linux/mutex.h>
+#include <linux/of.h>
 
 #include <asm/irq.h>
 #include <asm/uaccess.h>
@@ -2540,6 +2541,35 @@ void uart_insert_char(struct uart_port *port, unsigned int status,
 }
 EXPORT_SYMBOL_GPL(uart_insert_char);
 
+#ifdef CONFIG_OF
+/**
+ * of_uart_is_stdoutpath - check if this device matches the linux,stdout-path
+ *                         property
+ *
+ * Check if this device matches the linux,stdout-path property
+ * in the chosen node. return true if yes, false otherwise.
+ */
+int of_uart_is_stdoutpath(struct device *dev)
+{
+	struct device_node *dn;
+	const char *name;
+
+	name = of_get_property(of_chosen, "linux,stdout-path", NULL);
+	if (name == NULL)
+		return 0;
+
+	dn = of_find_node_by_path(name);
+	if (!dn)
+		return 0;
+
+	if (dn == dev->of_node)
+		return 1;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(of_uart_is_stdoutpath);
+#endif
+
 EXPORT_SYMBOL(uart_write_wakeup);
 EXPORT_SYMBOL(uart_register_driver);
 EXPORT_SYMBOL(uart_unregister_driver);
diff --git a/include/linux/serial_core.h b/include/linux/serial_core.h
index 0253c20..35a61f6 100644
--- a/include/linux/serial_core.h
+++ b/include/linux/serial_core.h
@@ -560,6 +560,9 @@ static inline int uart_handle_break(struct uart_port *port)
 					 (cflag) & CRTSCTS || \
 					 !((cflag) & CLOCAL))
 
+/* check if a device matches the linux,stdout-path property */
+int of_uart_is_stdoutpath(struct device *dev);
+
 #endif
 
 #endif /* LINUX_SERIAL_CORE_H */
-- 
1.7.10.4

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