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/* SPDX-License-Identifier: GPL-2.0 */
* LCD Lowlevel Control Abstraction
* Copyright (C) 2003,2004 Hewlett-Packard Company
#ifndef _LINUX_LCD_H
#define _LINUX_LCD_H
#include <linux/device.h>
#include <linux/mutex.h>
#include <linux/notifier.h>
#include <linux/fb.h>
/* Notes on locking:
* lcd_device->ops_lock is an internal backlight lock protecting the ops
* field and no code outside the core should need to touch it.
* Access to set_power() is serialised by the update_lock mutex since
* most drivers seem to need this and historically get it wrong.
* Most drivers don't need locking on their get_power() method.
* If yours does, you need to implement it in the driver. You can use the
* update_lock mutex if appropriate.
* Any other use of the locks below is probably wrong.
struct lcd_device;
struct fb_info;
struct lcd_properties {
/* The maximum value for contrast (read-only) */
int max_contrast;
struct lcd_ops {
/* Get the LCD panel power status (0: full on, 1..3: controller
power on, flat panel power off, 4: full off), see FB_BLANK_XXX */
int (*get_power)(struct lcd_device *);
* Enable or disable power to the LCD(0: on; 4: off, see FB_BLANK_XXX)
* and this callback would be called proir to fb driver's callback.
* P.S. note that if early_set_power is not NULL then early fb notifier
* would be registered.
int (*early_set_power)(struct lcd_device *, int power);
/* revert the effects of the early blank event. */
int (*r_early_set_power)(struct lcd_device *, int power);
/* Enable or disable power to the LCD (0: on; 4: off, see FB_BLANK_XXX) */
int (*set_power)(struct lcd_device *, int power);
/* Get the current contrast setting (0-max_contrast) */
int (*get_contrast)(struct lcd_device *);
/* Set LCD panel contrast */
int (*set_contrast)(struct lcd_device *, int contrast);
/* Set LCD panel mode (resolutions ...) */
int (*set_mode)(struct lcd_device *, struct fb_videomode *);
/* Check if given framebuffer device is the one LCD is bound to;
return 0 if not, !=0 if it is. If NULL, lcd always matches the fb. */
int (*check_fb)(struct lcd_device *, struct fb_info *);
struct lcd_device {
struct lcd_properties props;
/* This protects the 'ops' field. 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. */
struct mutex ops_lock;
/* If this is NULL, the backing module is unloaded */
struct lcd_ops *ops;
/* Serialise access to set_power method */
struct mutex update_lock;
/* The framebuffer notifier block */
struct notifier_block fb_notif;
struct device dev;
struct lcd_platform_data {
/* reset lcd panel device. */
int (*reset)(struct lcd_device *ld);
/* on or off to lcd panel. if 'enable' is 0 then
lcd power off and 1, lcd power on. */
int (*power_on)(struct lcd_device *ld, int enable);
/* it indicates whether lcd panel was enabled
from bootloader or not. */
int lcd_enabled;
/* it means delay for stable time when it becomes low to high
or high to low that is dependent on whether reset gpio is
low active or high active. */
unsigned int reset_delay;
/* stable time needing to become lcd power on. */
unsigned int power_on_delay;
/* stable time needing to become lcd power off. */
unsigned int power_off_delay;
/* it could be used for any purpose. */
void *pdata;
static inline void lcd_set_power(struct lcd_device *ld, int power)
if (ld->ops && ld->ops->set_power)
ld->ops->set_power(ld, power);
extern struct lcd_device *lcd_device_register(const char *name,
struct device *parent, void *devdata, struct lcd_ops *ops);
extern struct lcd_device *devm_lcd_device_register(struct device *dev,
const char *name, struct device *parent,
void *devdata, struct lcd_ops *ops);
extern void lcd_device_unregister(struct lcd_device *ld);
extern void devm_lcd_device_unregister(struct device *dev,
struct lcd_device *ld);
#define to_lcd_device(obj) container_of(obj, struct lcd_device, dev)
static inline void * lcd_get_data(struct lcd_device *ld_dev)
return dev_get_drvdata(&ld_dev->dev);