From c2adda27d202fa8f70a5d6e8b0c12b449c8868b8 Mon Sep 17 00:00:00 2001
From: Meghana Madhyastha <meghana.madhyastha@gmail.com>
Date: Wed, 24 Jan 2018 16:35:30 +0000
Subject: video: backlight: Add of_find_backlight helper in backlight.c
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Git-commit: c2adda27d202fa8f70a5d6e8b0c12b449c8868b8
Patch-mainline: v4.17-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166 bsc#1090888

Add of_find_backlight, a helper function which is a generic version
of tinydrm_of_find_backlight that can be used by other drivers to avoid
repetition of code and simplify things.

Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Reviewed-by: Sean Paul <seanpaul@chromium.org>
Reviewed-by: Thierry Reding <treding@nvidia.com>
Signed-off-by: Meghana Madhyastha <meghana.madhyastha@gmail.com>
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Link: https://patchwork.freedesktop.org/patch/msgid/116d160ba78be2e6dcbdcb6855622bce67da9472.1516810725.git.meghana.madhyastha@gmail.com
Acked-by: Thomas Zimmermann <tzimmermann@suse.de>
---
 drivers/video/backlight/backlight.c |   43 ++++++++++++++++++++++++++++++++++++
 include/linux/backlight.h           |   19 +++++++++++++++
 2 files changed, 62 insertions(+)

--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -575,6 +575,49 @@ struct backlight_device *of_find_backlig
 EXPORT_SYMBOL(of_find_backlight_by_node);
 #endif
 
+/**
+ * of_find_backlight - Get backlight device
+ * @dev: Device
+ *
+ * This function looks for a property named 'backlight' on the DT node
+ * connected to @dev and looks up the backlight device.
+ *
+ * Call backlight_put() to drop the reference on the backlight device.
+ *
+ * Returns:
+ * A pointer to the backlight device if found.
+ * Error pointer -EPROBE_DEFER if the DT property is set, but no backlight
+ * device is found.
+ * NULL if there's no backlight property.
+ */
+struct backlight_device *of_find_backlight(struct device *dev)
+{
+	struct backlight_device *bd = NULL;
+	struct device_node *np;
+
+	if (!dev)
+		return NULL;
+
+	if (IS_ENABLED(CONFIG_OF) && dev->of_node) {
+		np = of_parse_phandle(dev->of_node, "backlight", 0);
+		if (np) {
+			bd = of_find_backlight_by_node(np);
+			of_node_put(np);
+			if (!bd)
+				return ERR_PTR(-EPROBE_DEFER);
+			/*
+			 * Note: gpio_backlight uses brightness as
+			 * power state during probe
+			 */
+			if (!bd->props.brightness)
+				bd->props.brightness = bd->props.max_brightness;
+		}
+	}
+
+	return bd;
+}
+EXPORT_SYMBOL(of_find_backlight);
+
 static void __exit backlight_class_exit(void)
 {
 	class_destroy(backlight_class);
--- a/include/linux/backlight.h
+++ b/include/linux/backlight.h
@@ -129,6 +129,16 @@ static inline int backlight_disable(stru
 	return backlight_update_status(bd);
 }
 
+/**
+ * backlight_put - Drop backlight reference
+ * @bd: the backlight device to put
+ */
+static inline void backlight_put(struct backlight_device *bd)
+{
+	if (bd)
+		put_device(&bd->dev);
+}
+
 extern struct backlight_device *backlight_device_register(const char *name,
 	struct device *dev, void *devdata, const struct backlight_ops *ops,
 	const struct backlight_properties *props);
@@ -170,6 +180,15 @@ of_find_backlight_by_node(struct device_
 {
 	return NULL;
 }
+#endif
+
+#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
+struct backlight_device *of_find_backlight(struct device *dev);
+#else
+static inline struct backlight_device *of_find_backlight(struct device *dev)
+{
+	return NULL;
+}
 #endif
 
 #endif