[RFC PATCH] video:backlight: add dimming sysfs node

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In backlight class, update_status() callback function is mostly used to change
backlight brightness. When platform enter the dimming state, it is usually used.
But, I think dimming state can be defined variety of method including brightness.
So, it is need to differentiated node from brightness node.

In set_dimming() callback function, developers can define variety dimming functions.

Signed-off-by: Donghwa Lee <dh09.lee@xxxxxxxxxxx>
Signed-off-by: Inki Dae <inki.dae@xxxxxxxxxxx>
Signed-off-by: Kyungmin Park <kyungmin.park@xxxxxxxxxxx>
---
 drivers/video/backlight/backlight.c |   37 +++++++++++++++++++++++++++++++++++
 include/linux/backlight.h           |    9 ++++++++
 2 files changed, 46 insertions(+), 0 deletions(-)

diff --git a/drivers/video/backlight/backlight.c b/drivers/video/backlight/backlight.c
index bf5b1ec..44a77e4 100644
--- a/drivers/video/backlight/backlight.c
+++ b/drivers/video/backlight/backlight.c
@@ -101,6 +101,43 @@ static void backlight_generate_event(struct backlight_device *bd,
 	sysfs_notify(&bd->dev.kobj, NULL, "actual_brightness");
 }
 
+static ssize_t backlight_store_dimming(struct device *dev,
+		struct device_attribute *attr, const char *buf, size_t count)
+{
+	int rc;
+	struct backlight_device *bd = to_backlight_device(dev);
+	unsigned long dimming;
+
+	rc = strict_strtoul(buf, 0, &dimming);
+	if (rc)
+		return rc;
+
+	if (dimming < 0)
+		rc = -EINVAL;
+	else {
+		pr_debug("set dimming mode\n");
+
+		if (dimming)
+			bd->props.dimming = true;
+		else
+			bd->props.dimming = false;
+
+		backlight_set_dimming(bd);
+
+		rc = count;
+	}
+
+	return rc;
+}
+
+static ssize_t backlight_show_dimming(struct device *dev,
+		struct device_attribute *attr,char *buf)
+{
+	struct backlight_device *bd = to_backlight_device(dev);
+
+	return sprintf(buf, "%d\n", bd->props.dimming);
+}
+
 static ssize_t backlight_show_power(struct device *dev,
 		struct device_attribute *attr, char *buf)
 {
diff --git a/include/linux/backlight.h b/include/linux/backlight.h
index 5ffc6dd..823717e 100644
--- a/include/linux/backlight.h
+++ b/include/linux/backlight.h
@@ -55,10 +55,13 @@ struct backlight_ops {
 	/* Check if given framebuffer device is the one bound to this backlight;
 	   return 0 if not, !=0 if it is. If NULL, backlight always matches the fb. */
 	int (*check_fb)(struct backlight_device *, struct fb_info *);
+	/* Notify the backlight driver to enter the dimming state */
+	int (*set_dimming)(struct backlight_device *);
 };
 
 /* This structure defines all the properties of a backlight */
 struct backlight_properties {
+	bool dimming;
 	/* Current User requested brightness (0 - max_brightness) */
 	int brightness;
 	/* Maximal value for brightness (read-only) */
@@ -111,6 +114,12 @@ static inline void backlight_update_status(struct backlight_device *bd)
 	mutex_unlock(&bd->update_lock);
 }
 
+static inline void backlight_set_dimming(struct backlight_device *bd)
+{
+	if (bd->ops && bd->ops->set_dimming)
+		bd->ops->set_dimming(bd);
+}
+
 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);
-- 
1.7.4.1

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