include/linux/backlight.h - third_party/kernel - Git at Google

 /* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Backlight Lowlevel Control Abstraction
  *
  * Copyright (C) 2003,2004 Hewlett-Packard Company
  *
  */

 #ifndef _LINUX_BACKLIGHT_H
 #define _LINUX_BACKLIGHT_H

 #include <linux/device.h>
 #include <linux/fb.h>
 #include <linux/mutex.h>
 #include <linux/notifier.h>

 /**
  * enum backlight_update_reason - what method was used to update backlight
  *
  * A driver indicates the method (reason) used for updating the backlight
  * when calling backlight_force_update().
  */
 enum backlight_update_reason {
 	/**
 	 * @BACKLIGHT_UPDATE_HOTKEY: The backlight was updated using a hot-key.
 	 */
 	BACKLIGHT_UPDATE_HOTKEY,

 	/**
 	 * @BACKLIGHT_UPDATE_SYSFS: The backlight was updated using sysfs.
 	 */
 	BACKLIGHT_UPDATE_SYSFS,
 };

 /**
  * enum backlight_type - the type of backlight control
  *
  * The type of interface used to control the backlight.
  */
 enum backlight_type {
 	/**
 	 * @BACKLIGHT_RAW:
 	 *
 	 * The backlight is controlled using hardware registers.
 	 */
 	BACKLIGHT_RAW = 1,

 	/**
 	 * @BACKLIGHT_PLATFORM:
 	 *
 	 * The backlight is controlled using a platform-specific interface.
 	 */
 	BACKLIGHT_PLATFORM,

 	/**
 	 * @BACKLIGHT_FIRMWARE:
 	 *
 	 * The backlight is controlled using a standard firmware interface.
 	 */
 	BACKLIGHT_FIRMWARE,

 	/**
 	 * @BACKLIGHT_TYPE_MAX: Number of entries.
 	 */
 	BACKLIGHT_TYPE_MAX,
 };

 /**
  * enum backlight_notification - the type of notification
  *
  * The notifications that is used for notification sent to the receiver
  * that registered notifications using backlight_register_notifier().
  */
 enum backlight_notification {
 	/**
 	 * @BACKLIGHT_REGISTERED: The backlight device is registered.
 	 */
 	BACKLIGHT_REGISTERED,

 	/**
 	 * @BACKLIGHT_UNREGISTERED: The backlight revice is unregistered.
 	 */
 	BACKLIGHT_UNREGISTERED,
 };

 /** enum backlight_scale - the type of scale used for brightness values
  *
  * The type of scale used for brightness values.
  */
 enum backlight_scale {
 	/**
 	 * @BACKLIGHT_SCALE_UNKNOWN: The scale is unknown.
 	 */
 	BACKLIGHT_SCALE_UNKNOWN = 0,

 	/**
 	 * @BACKLIGHT_SCALE_LINEAR: The scale is linear.
 	 *
 	 * The linear scale will increase brightness the same for each step.
 	 */
 	BACKLIGHT_SCALE_LINEAR,

 	/**
 	 * @BACKLIGHT_SCALE_NON_LINEAR: The scale is not linear.
 	 *
 	 * This is often used when the brightness values tries to adjust to
 	 * the relative perception of the eye demanding a non-linear scale.
 	 */
 	BACKLIGHT_SCALE_NON_LINEAR,
 };

 struct backlight_device;
 struct fb_info;

 /**
  * struct backlight_ops - backlight operations
  *
  * The backlight operations are specified when the backlight device is registered.
  */
 struct backlight_ops {
 	/**
 	 * @options: Configure how operations are called from the core.
 	 *
 	 * The options parameter is used to adjust the behaviour of the core.
 	 * Set BL_CORE_SUSPENDRESUME to get the update_status() operation called
 	 * upon suspend and resume.
 	 */
 	unsigned int options;

 #define BL_CORE_SUSPENDRESUME	(1 << 0)

 	/**
 	 * @update_status: Operation called when properties have changed.
 	 *
 	 * Notify the backlight driver some property has changed.
 	 * The update_status operation is protected by the update_lock.
 	 *
 	 * The backlight driver is expected to use backlight_is_blank()
 	 * to check if the display is blanked and set brightness accordingly.
 	 * update_status() is called when any of the properties has changed.
 	 *
 	 * RETURNS:
 	 *
 	 * 0 on success, negative error code if any failure occurred.
 	 */
 	int (*update_status)(struct backlight_device *);

 	/**
 	 * @get_brightness: Return the current backlight brightness.
 	 *
 	 * The driver may implement this as a readback from the HW.
 	 * This operation is optional and if not present then the current
 	 * brightness property value is used.
 	 *
 	 * RETURNS:
 	 *
 	 * A brightness value which is 0 or a positive number.
 	 * On failure a negative error code is returned.
 	 */
 	int (*get_brightness)(struct backlight_device *);

 	/**
 	 * @check_fb: Check the framebuffer device.
 	 *
 	 * Check if given framebuffer device is the one bound to this backlight.
 	 * This operation is optional and if not implemented it is assumed that the
 	 * fbdev is always the one bound to the backlight.
 	 *
 	 * RETURNS:
 	 *
 	 * If info is NULL or the info matches the fbdev bound to the backlight return true.
 	 * If info does not match the fbdev bound to the backlight return false.
 	 */
 	int (*check_fb)(struct backlight_device *bd, struct fb_info *info);
 };

 /**
  * struct backlight_properties - backlight properties
  *
  * This structure defines all the properties of a backlight.
  */
 struct backlight_properties {
 	/**
 	 * @brightness: The current brightness requested by the user.
 	 *
 	 * The backlight core makes sure the range is (0 to max_brightness)
 	 * when the brightness is set via the sysfs attribute:
 	 * /sys/class/backlight/<backlight>/brightness.
 	 *
 	 * This value can be set in the backlight_properties passed
 	 * to devm_backlight_device_register() to set a default brightness
 	 * value.
 	 */
 	int brightness;

 	/**
 	 * @max_brightness: The maximum brightness value.
 	 *
 	 * This value must be set in the backlight_properties passed to
 	 * devm_backlight_device_register() and shall not be modified by the
 	 * driver after registration.
 	 */
 	int max_brightness;

 	/**
 	 * @power: The current power mode.
 	 *
 	 * User space can configure the power mode using the sysfs
 	 * attribute: /sys/class/backlight/<backlight>/bl_power
 	 * When the power property is updated update_status() is called.
 	 *
 	 * The possible values are: (0: full on, 1 to 3: power saving
 	 * modes; 4: full off), see FB_BLANK_XXX.
 	 *
 	 * When the backlight device is enabled @power is set
 	 * to FB_BLANK_UNBLANK. When the backlight device is disabled
 	 * @power is set to FB_BLANK_POWERDOWN.
 	 */
 	int power;

 	/**
 	 * @fb_blank: The power state from the FBIOBLANK ioctl.
 	 *
 	 * When the FBIOBLANK ioctl is called @fb_blank is set to the
 	 * blank parameter and the update_status() operation is called.
 	 *
 	 * When the backlight device is enabled @fb_blank is set
 	 * to FB_BLANK_UNBLANK. When the backlight device is disabled
 	 * @fb_blank is set to FB_BLANK_POWERDOWN.
 	 *
 	 * Backlight drivers should avoid using this property. It has been
 	 * replaced by state & BL_CORE_FBLANK (although most drivers should
 	 * use backlight_is_blank() as the preferred means to get the blank
 	 * state).
 	 *
 	 * fb_blank is deprecated and will be removed.
 	 */
 	int fb_blank;

 	/**
 	 * @type: The type of backlight supported.
 	 *
 	 * The backlight type allows userspace to make appropriate
 	 * policy decisions based on the backlight type.
 	 *
 	 * This value must be set in the backlight_properties
 	 * passed to devm_backlight_device_register().
 	 */
 	enum backlight_type type;

 	/**
 	 * @state: The state of the backlight core.
 	 *
 	 * The state is a bitmask. BL_CORE_FBBLANK is set when the display
 	 * is expected to be blank. BL_CORE_SUSPENDED is set when the
 	 * driver is suspended.
 	 *
 	 * backlight drivers are expected to use backlight_is_blank()
 	 * in their update_status() operation rather than reading the
 	 * state property.
 	 *
 	 * The state is maintained by the core and drivers may not modify it.
 	 */
 	unsigned int state;

 #define BL_CORE_SUSPENDED	(1 << 0)	/* backlight is suspended */
 #define BL_CORE_FBBLANK		(1 << 1)	/* backlight is under an fb blank event */

 	/**
 	 * @scale: The type of the brightness scale.
 	 */
 	enum backlight_scale scale;
 };

 /**
  * struct backlight_device - backlight device data
  *
  * This structure holds all data required by a backlight device.
  */
 struct backlight_device {
 	/**
 	 * @props: Backlight properties
 	 */
 	struct backlight_properties props;

 	/**
 	 * @update_lock: The lock used when calling the update_status() operation.
 	 *
 	 * update_lock is an internal backlight lock that serialise access
 	 * to the update_status() operation. The backlight core holds the update_lock
 	 * when calling the update_status() operation. The update_lock shall not
 	 * be used by backlight drivers.
 	 */
 	struct mutex update_lock;

 	/**
 	 * @ops_lock: The lock used around everything related to backlight_ops.
 	 *
 	 * ops_lock is an internal backlight lock that protects the ops pointer
 	 * and is used around all accesses to ops and when the operations are
 	 * invoked. The ops_lock shall not be used by backlight drivers.
 	 */
 	struct mutex ops_lock;

 	/**
 	 * @ops: Pointer to the backlight operations.
 	 *
 	 * If ops is NULL, the driver that registered this device has been unloaded,
 	 * and if class_get_devdata() points to something in the body of that driver,
 	 * it is also invalid.
 	 */
 	const struct backlight_ops *ops;

 	/**
 	 * @fb_notif: The framebuffer notifier block
 	 */
 	struct notifier_block fb_notif;

 	/**
 	 * @entry: List entry of all registered backlight devices
 	 */
 	struct list_head entry;

 	/**
 	 * @dev: Parent device.
 	 */
 	struct device dev;

 	/**
 	 * @fb_bl_on: The state of individual fbdev's.
 	 *
 	 * Multiple fbdev's may share one backlight device. The fb_bl_on
 	 * records the state of the individual fbdev.
 	 */
 	bool fb_bl_on[FB_MAX];

 	/**
 	 * @use_count: The number of uses of fb_bl_on.
 	 */
 	int use_count;
 };

 /**
  * backlight_update_status - force an update of the backlight device status
  * @bd: the backlight device
  */
 static inline int backlight_update_status(struct backlight_device *bd)
 {
 	int ret = -ENOENT;

 	mutex_lock(&bd->update_lock);
 	if (bd->ops && bd->ops->update_status)
 		ret = bd->ops->update_status(bd);
 	mutex_unlock(&bd->update_lock);

 	return ret;
 }

 /**
  * backlight_enable - Enable backlight
  * @bd: the backlight device to enable
  */
 static inline int backlight_enable(struct backlight_device *bd)
 {
 	if (!bd)
 		return 0;

 	bd->props.power = FB_BLANK_UNBLANK;
 	bd->props.fb_blank = FB_BLANK_UNBLANK;
 	bd->props.state &= ~BL_CORE_FBBLANK;

 	return backlight_update_status(bd);
 }

 /**
  * backlight_disable - Disable backlight
  * @bd: the backlight device to disable
  */
 static inline int backlight_disable(struct backlight_device *bd)
 {
 	if (!bd)
 		return 0;

 	bd->props.power = FB_BLANK_POWERDOWN;
 	bd->props.fb_blank = FB_BLANK_POWERDOWN;
 	bd->props.state |= BL_CORE_FBBLANK;

 	return backlight_update_status(bd);
 }

 /**
  * backlight_is_blank - Return true if display is expected to be blank
  * @bd: the backlight device
  *
  * Display is expected to be blank if any of these is true::
  *
  *   1) if power in not UNBLANK
  *   2) if fb_blank is not UNBLANK
  *   3) if state indicate BLANK or SUSPENDED
  *
  * Returns true if display is expected to be blank, false otherwise.
  */
 static inline bool backlight_is_blank(const struct backlight_device *bd)
 {
 	return bd->props.power != FB_BLANK_UNBLANK ||
 	       bd->props.fb_blank != FB_BLANK_UNBLANK ||
 	       bd->props.state & (BL_CORE_SUSPENDED | BL_CORE_FBBLANK);
 }

 /**
  * backlight_get_brightness - Returns the current brightness value
  * @bd: the backlight device
  *
  * Returns the current brightness value, taking in consideration the current
  * state. If backlight_is_blank() returns true then return 0 as brightness
  * otherwise return the current brightness property value.
  *
  * Backlight drivers are expected to use this function in their update_status()
  * operation to get the brightness value.
  */
 static inline int backlight_get_brightness(const struct backlight_device *bd)
 {
 	if (backlight_is_blank(bd))
 		return 0;
 	else
 		return bd->props.brightness;
 }

 struct backlight_device *
 backlight_device_register(const char *name, struct device *dev, void *devdata,
 			  const struct backlight_ops *ops,
 			  const struct backlight_properties *props);
 struct backlight_device *
 devm_backlight_device_register(struct device *dev, const char *name,
 			       struct device *parent, void *devdata,
 			       const struct backlight_ops *ops,
 			       const struct backlight_properties *props);
 void backlight_device_unregister(struct backlight_device *bd);
 void devm_backlight_device_unregister(struct device *dev,
 				      struct backlight_device *bd);
 void backlight_force_update(struct backlight_device *bd,
 			    enum backlight_update_reason reason);
 int backlight_register_notifier(struct notifier_block *nb);
 int backlight_unregister_notifier(struct notifier_block *nb);
 struct backlight_device *backlight_device_get_by_name(const char *name);
 struct backlight_device *backlight_device_get_by_type(enum backlight_type type);
 int backlight_device_set_brightness(struct backlight_device *bd,
 				    unsigned long brightness);

 #define to_backlight_device(obj) container_of(obj, struct backlight_device, dev)

 /**
  * bl_get_data - access devdata
  * @bl_dev: pointer to backlight device
  *
  * When a backlight device is registered the driver has the possibility
  * to supply a void * devdata. bl_get_data() return a pointer to the
  * devdata.
  *
  * RETURNS:
  *
  * pointer to devdata stored while registering the backlight device.
  */
 static inline void * bl_get_data(struct backlight_device *bl_dev)
 {
 	return dev_get_drvdata(&bl_dev->dev);
 }

 #ifdef 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

 #if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
 struct backlight_device *devm_of_find_backlight(struct device *dev);
 #else
 static inline struct backlight_device *
 devm_of_find_backlight(struct device *dev)
 {
 	return NULL;
 }
 #endif

 #endif
	/* SPDX-License-Identifier: GPL-2.0 */
	/*
	* Backlight Lowlevel Control Abstraction
	*
	* Copyright (C) 2003,2004 Hewlett-Packard Company
	*
	*/

	#ifndef _LINUX_BACKLIGHT_H
	#define _LINUX_BACKLIGHT_H

	#include <linux/device.h>
	#include <linux/fb.h>
	#include <linux/mutex.h>
	#include <linux/notifier.h>

	/**
	* enum backlight_update_reason - what method was used to update backlight
	*
	* A driver indicates the method (reason) used for updating the backlight
	* when calling backlight_force_update().
	*/
	enum backlight_update_reason {
	/**
	* @BACKLIGHT_UPDATE_HOTKEY: The backlight was updated using a hot-key.
	*/
	BACKLIGHT_UPDATE_HOTKEY,

	/**
	* @BACKLIGHT_UPDATE_SYSFS: The backlight was updated using sysfs.
	*/
	BACKLIGHT_UPDATE_SYSFS,
	};

	/**
	* enum backlight_type - the type of backlight control
	*
	* The type of interface used to control the backlight.
	*/
	enum backlight_type {
	/**
	* @BACKLIGHT_RAW:
	*
	* The backlight is controlled using hardware registers.
	*/
	BACKLIGHT_RAW = 1,

	/**
	* @BACKLIGHT_PLATFORM:
	*
	* The backlight is controlled using a platform-specific interface.
	*/
	BACKLIGHT_PLATFORM,

	/**
	* @BACKLIGHT_FIRMWARE:
	*
	* The backlight is controlled using a standard firmware interface.
	*/
	BACKLIGHT_FIRMWARE,

	/**
	* @BACKLIGHT_TYPE_MAX: Number of entries.
	*/
	BACKLIGHT_TYPE_MAX,
	};

	/**
	* enum backlight_notification - the type of notification
	*
	* The notifications that is used for notification sent to the receiver
	* that registered notifications using backlight_register_notifier().
	*/
	enum backlight_notification {
	/**
	* @BACKLIGHT_REGISTERED: The backlight device is registered.
	*/
	BACKLIGHT_REGISTERED,

	/**
	* @BACKLIGHT_UNREGISTERED: The backlight revice is unregistered.
	*/
	BACKLIGHT_UNREGISTERED,
	};

	/** enum backlight_scale - the type of scale used for brightness values
	*
	* The type of scale used for brightness values.
	*/
	enum backlight_scale {
	/**
	* @BACKLIGHT_SCALE_UNKNOWN: The scale is unknown.
	*/
	BACKLIGHT_SCALE_UNKNOWN = 0,

	/**
	* @BACKLIGHT_SCALE_LINEAR: The scale is linear.
	*
	* The linear scale will increase brightness the same for each step.
	*/
	BACKLIGHT_SCALE_LINEAR,

	/**
	* @BACKLIGHT_SCALE_NON_LINEAR: The scale is not linear.
	*
	* This is often used when the brightness values tries to adjust to
	* the relative perception of the eye demanding a non-linear scale.
	*/
	BACKLIGHT_SCALE_NON_LINEAR,
	};

	struct backlight_device;
	struct fb_info;

	/**
	* struct backlight_ops - backlight operations
	*
	* The backlight operations are specified when the backlight device is registered.
	*/
	struct backlight_ops {
	/**
	* @options: Configure how operations are called from the core.
	*
	* The options parameter is used to adjust the behaviour of the core.
	* Set BL_CORE_SUSPENDRESUME to get the update_status() operation called
	* upon suspend and resume.
	*/
	unsigned int options;

	#define BL_CORE_SUSPENDRESUME (1 << 0)

	/**
	* @update_status: Operation called when properties have changed.
	*
	* Notify the backlight driver some property has changed.
	* The update_status operation is protected by the update_lock.
	*
	* The backlight driver is expected to use backlight_is_blank()
	* to check if the display is blanked and set brightness accordingly.
	* update_status() is called when any of the properties has changed.
	*
	* RETURNS:
	*
	* 0 on success, negative error code if any failure occurred.
	*/
	int (update_status)(struct backlight_device );

	/**
	* @get_brightness: Return the current backlight brightness.
	*
	* The driver may implement this as a readback from the HW.
	* This operation is optional and if not present then the current
	* brightness property value is used.
	*
	* RETURNS:
	*
	* A brightness value which is 0 or a positive number.
	* On failure a negative error code is returned.
	*/
	int (get_brightness)(struct backlight_device );

	/**
	* @check_fb: Check the framebuffer device.
	*
	* Check if given framebuffer device is the one bound to this backlight.
	* This operation is optional and if not implemented it is assumed that the
	* fbdev is always the one bound to the backlight.
	*
	* RETURNS:
	*
	* If info is NULL or the info matches the fbdev bound to the backlight return true.
	* If info does not match the fbdev bound to the backlight return false.
	*/
	int (check_fb)(struct backlight_device bd, struct fb_info *info);
	};

	/**
	* struct backlight_properties - backlight properties
	*
	* This structure defines all the properties of a backlight.
	*/
	struct backlight_properties {
	/**
	* @brightness: The current brightness requested by the user.
	*
	* The backlight core makes sure the range is (0 to max_brightness)
	* when the brightness is set via the sysfs attribute:
	* /sys/class/backlight/<backlight>/brightness.
	*
	* This value can be set in the backlight_properties passed
	* to devm_backlight_device_register() to set a default brightness
	* value.
	*/
	int brightness;

	/**
	* @max_brightness: The maximum brightness value.
	*
	* This value must be set in the backlight_properties passed to
	* devm_backlight_device_register() and shall not be modified by the
	* driver after registration.
	*/
	int max_brightness;

	/**
	* @power: The current power mode.
	*
	* User space can configure the power mode using the sysfs
	* attribute: /sys/class/backlight/<backlight>/bl_power
	* When the power property is updated update_status() is called.
	*
	* The possible values are: (0: full on, 1 to 3: power saving
	* modes; 4: full off), see FB_BLANK_XXX.
	*
	* When the backlight device is enabled @power is set
	* to FB_BLANK_UNBLANK. When the backlight device is disabled
	* @power is set to FB_BLANK_POWERDOWN.
	*/
	int power;

	/**
	* @fb_blank: The power state from the FBIOBLANK ioctl.
	*
	* When the FBIOBLANK ioctl is called @fb_blank is set to the
	* blank parameter and the update_status() operation is called.
	*
	* When the backlight device is enabled @fb_blank is set
	* to FB_BLANK_UNBLANK. When the backlight device is disabled
	* @fb_blank is set to FB_BLANK_POWERDOWN.
	*
	* Backlight drivers should avoid using this property. It has been
	* replaced by state & BL_CORE_FBLANK (although most drivers should
	* use backlight_is_blank() as the preferred means to get the blank
	* state).
	*
	* fb_blank is deprecated and will be removed.
	*/
	int fb_blank;

	/**
	* @type: The type of backlight supported.
	*
	* The backlight type allows userspace to make appropriate
	* policy decisions based on the backlight type.
	*
	* This value must be set in the backlight_properties
	* passed to devm_backlight_device_register().
	*/
	enum backlight_type type;

	/**
	* @state: The state of the backlight core.
	*
	* The state is a bitmask. BL_CORE_FBBLANK is set when the display
	* is expected to be blank. BL_CORE_SUSPENDED is set when the
	* driver is suspended.
	*
	* backlight drivers are expected to use backlight_is_blank()
	* in their update_status() operation rather than reading the
	* state property.
	*
	* The state is maintained by the core and drivers may not modify it.
	*/
	unsigned int state;

	#define BL_CORE_SUSPENDED (1 << 0) /* backlight is suspended */
	#define BL_CORE_FBBLANK (1 << 1) /* backlight is under an fb blank event */

	/**
	* @scale: The type of the brightness scale.
	*/
	enum backlight_scale scale;
	};

	/**
	* struct backlight_device - backlight device data
	*
	* This structure holds all data required by a backlight device.
	*/
	struct backlight_device {
	/**
	* @props: Backlight properties
	*/
	struct backlight_properties props;

	/**
	* @update_lock: The lock used when calling the update_status() operation.
	*
	* update_lock is an internal backlight lock that serialise access
	* to the update_status() operation. The backlight core holds the update_lock
	* when calling the update_status() operation. The update_lock shall not
	* be used by backlight drivers.
	*/
	struct mutex update_lock;

	/**
	* @ops_lock: The lock used around everything related to backlight_ops.
	*
	* ops_lock is an internal backlight lock that protects the ops pointer
	* and is used around all accesses to ops and when the operations are
	* invoked. The ops_lock shall not be used by backlight drivers.
	*/
	struct mutex ops_lock;

	/**
	* @ops: Pointer to the backlight operations.
	*
	* If ops is NULL, the driver that registered this device has been unloaded,
	* and if class_get_devdata() points to something in the body of that driver,
	* it is also invalid.
	*/
	const struct backlight_ops *ops;

	/**
	* @fb_notif: The framebuffer notifier block
	*/
	struct notifier_block fb_notif;

	/**
	* @entry: List entry of all registered backlight devices
	*/
	struct list_head entry;

	/**
	* @dev: Parent device.
	*/
	struct device dev;

	/**
	* @fb_bl_on: The state of individual fbdev's.
	*
	* Multiple fbdev's may share one backlight device. The fb_bl_on
	* records the state of the individual fbdev.
	*/
	bool fb_bl_on[FB_MAX];

	/**
	* @use_count: The number of uses of fb_bl_on.
	*/
	int use_count;
	};

	/**
	* backlight_update_status - force an update of the backlight device status
	* @bd: the backlight device
	*/
	static inline int backlight_update_status(struct backlight_device *bd)
	{
	int ret = -ENOENT;

	mutex_lock(&bd->update_lock);
	if (bd->ops && bd->ops->update_status)
	ret = bd->ops->update_status(bd);
	mutex_unlock(&bd->update_lock);

	return ret;
	}

	/**
	* backlight_enable - Enable backlight
	* @bd: the backlight device to enable
	*/
	static inline int backlight_enable(struct backlight_device *bd)
	{
	if (!bd)
	return 0;

	bd->props.power = FB_BLANK_UNBLANK;
	bd->props.fb_blank = FB_BLANK_UNBLANK;
	bd->props.state &= ~BL_CORE_FBBLANK;

	return backlight_update_status(bd);
	}

	/**
	* backlight_disable - Disable backlight
	* @bd: the backlight device to disable
	*/
	static inline int backlight_disable(struct backlight_device *bd)
	{
	if (!bd)
	return 0;

	bd->props.power = FB_BLANK_POWERDOWN;
	bd->props.fb_blank = FB_BLANK_POWERDOWN;
	bd->props.state \|= BL_CORE_FBBLANK;

	return backlight_update_status(bd);
	}

	/**
	* backlight_is_blank - Return true if display is expected to be blank
	* @bd: the backlight device
	*
	* Display is expected to be blank if any of these is true::
	*
	* 1) if power in not UNBLANK
	* 2) if fb_blank is not UNBLANK
	* 3) if state indicate BLANK or SUSPENDED
	*
	* Returns true if display is expected to be blank, false otherwise.
	*/
	static inline bool backlight_is_blank(const struct backlight_device *bd)
	{
	return bd->props.power != FB_BLANK_UNBLANK \|\|
	bd->props.fb_blank != FB_BLANK_UNBLANK \|\|
	bd->props.state & (BL_CORE_SUSPENDED \| BL_CORE_FBBLANK);
	}

	/**
	* backlight_get_brightness - Returns the current brightness value
	* @bd: the backlight device
	*
	* Returns the current brightness value, taking in consideration the current
	* state. If backlight_is_blank() returns true then return 0 as brightness
	* otherwise return the current brightness property value.
	*
	* Backlight drivers are expected to use this function in their update_status()
	* operation to get the brightness value.
	*/
	static inline int backlight_get_brightness(const struct backlight_device *bd)
	{
	if (backlight_is_blank(bd))
	return 0;
	else
	return bd->props.brightness;
	}

	struct backlight_device *
	backlight_device_register(const char name, struct device dev, void *devdata,
	const struct backlight_ops *ops,
	const struct backlight_properties *props);
	struct backlight_device *
	devm_backlight_device_register(struct device dev, const char name,
	struct device parent, void devdata,
	const struct backlight_ops *ops,
	const struct backlight_properties *props);
	void backlight_device_unregister(struct backlight_device *bd);
	void devm_backlight_device_unregister(struct device *dev,
	struct backlight_device *bd);
	void backlight_force_update(struct backlight_device *bd,
	enum backlight_update_reason reason);
	int backlight_register_notifier(struct notifier_block *nb);
	int backlight_unregister_notifier(struct notifier_block *nb);
	struct backlight_device backlight_device_get_by_name(const char name);
	struct backlight_device *backlight_device_get_by_type(enum backlight_type type);
	int backlight_device_set_brightness(struct backlight_device *bd,
	unsigned long brightness);

	#define to_backlight_device(obj) container_of(obj, struct backlight_device, dev)

	/**
	* bl_get_data - access devdata
	* @bl_dev: pointer to backlight device
	*
	* When a backlight device is registered the driver has the possibility
	* to supply a void * devdata. bl_get_data() return a pointer to the
	* devdata.
	*
	* RETURNS:
	*
	* pointer to devdata stored while registering the backlight device.
	*/
	static inline void * bl_get_data(struct backlight_device *bl_dev)
	{
	return dev_get_drvdata(&bl_dev->dev);
	}

	#ifdef 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

	#if IS_ENABLED(CONFIG_BACKLIGHT_CLASS_DEVICE)
	struct backlight_device devm_of_find_backlight(struct device dev);
	#else
	static inline struct backlight_device *
	devm_of_find_backlight(struct device *dev)
	{
	return NULL;
	}
	#endif

	#endif