linux-kernel - [PATCH] backlight: Add of_find_backlight_by

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Message-Id: <1352469878-4532-1-git-send-email-thierry.reding@avionic-design.de>
Date:	Fri,  9 Nov 2012 15:04:38 +0100
From:	Thierry Reding <thierry.reding@...onic-design.de>
To:	Richard Purdie <rpurdie@...ys.net>,
	Florian Tobias Schandinat <FlorianSchandinat@....de>
Cc:	linux-fbdev@...r.kernel.org, devicetree-discuss@...ts.ozlabs.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] backlight: Add of_find_backlight_by_node() function

This function finds the struct backlight_device for a given device tree
node. A dummy function is provided so that it safely compiles out if OF
support is disabled.

Signed-off-by: Thierry Reding <thierry.reding@...onic-design.de>
---
 drivers/video/backlight/backlight.c | 17 +++++++++++++++++
 include/linux/backlight.h           | 10 ++++++++++
 2 files changed, 27 insertions(+)

diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index 297db2f..0d1ed4f 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -370,6 +370,23 @@ void backlight_device_unregister(struct backlight_device *bd)
 }
 EXPORT_SYMBOL(backlight_device_unregister);
 
+#if IS_ENABLED(CONFIG_OF)
+static int of_parent_match(struct device *dev, void *data)
+{
+	return dev->parent && dev->parent->of_node == data;
+}
+
+struct backlight_device *of_find_backlight_by_node(struct device_node *node)
+{
+	struct device *dev;
+
+	dev = class_find_device(backlight_class, NULL, node, of_parent_match);
+
+	return dev ? to_backlight_device(dev) : NULL;
+}
+EXPORT_SYMBOL(of_find_backlight_by_node);
+#endif
+
 static void __exit backlight_class_exit(void)
 {
 	class_destroy(backlight_class);
diff --git a/include/linux/backlight.h b/include/linux/backlight.h
index 5ffc6dd..11840e9 100644
--- a/include/linux/backlight.h
+++ b/include/linux/backlight.h
@@ -134,4 +134,14 @@ struct generic_bl_info {
 	void (*kick_battery)(void);
 };
 
+#if IS_ENABLED(CONFIG_OF)
+struct backlight_device *of_find_backlight_by_node(struct device_node *node);
+#else
+static inline struct backlight_device *
+of_find_backlight_by_node(struct device_node *node)
+{
+	return NULL;
+}
+#endif
+
 #endif
-- 
1.8.0

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