include/linux/backlight.h

   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
  30 struct backlight_device;
  31 struct fb_info;
  32
  33 struct 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 */
  45 struct 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
  57 struct 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
  76 static 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
  84 extern struct backlight_device *backlight_device_register(const char *name,
  85         struct device *dev, void *devdata, struct backlight_ops *ops);
  86 extern 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