linux-kernel - [PATCH v17 03/10] video: backlight: Add of_find

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Date:   Fri, 19 Jan 2018 10:42:15 +0000
From:   Meghana Madhyastha <meghana.madhyastha@...il.com>
To:     Lee Jones <lee.jones@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Noralf Trønnes <noralf@...nnes.org>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        Sean Paul <seanpaul@...omium.org>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org
Subject: [PATCH v17 03/10] video: backlight: Add of_find_backlight helper in
 backlight.c

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.

Signed-off-by: Meghana Madhyastha <meghana.madhyastha@...il.com>
---
changes in v17:
-rebase with drm-misc-next
-convert st7735r callers from tinydrm specific helpers
 to new generic backlight helpers
-remove select BACKLIGHT_LCD_SUPPORT
 and select BACKLIGHT_CLASS_DEVICE from
 tinydrm/Kconfig

 drivers/video/backlight/backlight.c | 43 +++++++++++++++++++++++++++++++++++++
 include/linux/backlight.h           | 19 ++++++++++++++++
 2 files changed, 62 insertions(+)

diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index 8049e7656..553bf5c48 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -580,6 +580,49 @@ struct backlight_device *of_find_backlight_by_node(struct device_node *node)
 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);
diff --git a/include/linux/backlight.h b/include/linux/backlight.h
index ace825e2c..ddc9bade4 100644
--- a/include/linux/backlight.h
+++ b/include/linux/backlight.h
@@ -162,6 +162,16 @@ static inline int backlight_disable(struct backlight_device *bd)
 	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);
@@ -205,4 +215,13 @@ of_find_backlight_by_node(struct device_node *node)
 }
 #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
-- 
2.11.0