1/*
2 * Backlight Lowlevel Control Abstraction
3 *
4 * Copyright (C) 2003,2004 Hewlett-Packard Company
5 *
6 */
7
8#ifndef _LINUX_BACKLIGHT_H
9#define _LINUX_BACKLIGHT_H
10
11#include <linux/device.h>
12#include <linux/mutex.h>
13#include <linux/notifier.h>
14
15/* Notes on locking:
16 *
17 * backlight_device->ops_lock is an internal backlight lock protecting the
18 * ops pointer and no code outside the core should need to touch it.
19 *
20 * Access to update_status() is serialised by the update_lock mutex since
21 * most drivers seem to need this and historically get it wrong.
22 *
23 * Most drivers don't need locking on their get_brightness() method.
24 * If yours does, you need to implement it in the driver. You can use the
25 * update_lock mutex if appropriate.
26 *
27 * Any other use of the locks below is probably wrong.
28 */
29
30struct backlight_device;
31struct fb_info;
32
33struct backlight_ops {
34	/* Notify the backlight driver some property has changed */
35	int (*update_status)(struct backlight_device *);
36	/* Return the current backlight brightness (accounting for power,
37	   fb_blank etc.) */
38	int (*get_brightness)(struct backlight_device *);
39	/* Check if given framebuffer device is the one bound to this backlight;
40	   return 0 if not, !=0 if it is. If NULL, backlight always matches the fb. */
41	int (*check_fb)(struct fb_info *);
42};
43
44/* This structure defines all the properties of a backlight */
45struct backlight_properties {
46	/* Current User requested brightness (0 - max_brightness) */
47	int brightness;
48	/* Maximal value for brightness (read-only) */
49	int max_brightness;
50	/* Current FB Power mode (0: full on, 1..3: power saving
51	   modes; 4: full off), see FB_BLANK_XXX */
52	int power;
53	/* FB Blanking active? (values as for power) */
54	int fb_blank;
55};
56
57struct backlight_device {
58	/* Backlight properties */
59	struct backlight_properties props;
60
61	/* Serialise access to update_status method */
62	struct mutex update_lock;
63
64	/* This protects the 'ops' field. If 'ops' is NULL, the driver that
65	   registered this device has been unloaded, and if class_get_devdata()
66	   points to something in the body of that driver, it is also invalid. */
67	struct mutex ops_lock;
68	struct backlight_ops *ops;
69
70	/* The framebuffer notifier block */
71	struct notifier_block fb_notif;
72	/* The class device structure */
73	struct class_device class_dev;
74};
75
76static inline void backlight_update_status(struct backlight_device *bd)
77{
78	mutex_lock(&bd->update_lock);
79	if (bd->ops && bd->ops->update_status)
80		bd->ops->update_status(bd);
81	mutex_unlock(&bd->update_lock);
82}
83
84extern struct backlight_device *backlight_device_register(const char *name,
85	struct device *dev, void *devdata, struct backlight_ops *ops);
86extern void backlight_device_unregister(struct backlight_device *bd);
87
88#define to_backlight_device(obj) container_of(obj, struct backlight_device, class_dev)
89
90#endif
91