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->sem is an internal backlight lock protecting the props
  18  * field 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 /* This structure defines all the properties of a backlight
  34    (usually attached to a LCD). */
  35 struct backlight_properties {
  36         /* Notify the backlight driver some property has changed */
  37         int (*update_status)(struct backlight_device *);
  38         /* Return the current backlight brightness (accounting for power,
  39            fb_blank etc.) */
  40         int (*get_brightness)(struct backlight_device *);
  41         /* Check if given framebuffer device is the one bound to this backlight;
  42            return 0 if not, !=0 if it is. If NULL, backlight always matches the fb. */
  43         int (*check_fb)(struct fb_info *);
  44
  45         /* Current User requested brightness (0 - max_brightness) */
  46         int brightness;
  47         /* Maximal value for brightness (read-only) */
  48         int max_brightness;
  49         /* Current FB Power mode (0: full on, 1..3: power saving
  50            modes; 4: full off), see FB_BLANK_XXX */
  51         int power;
  52         /* FB Blanking active? (values as for power) */
  53         int fb_blank;
  54 };
  55
  56 struct backlight_device {
  57         /* This protects the 'props' field. If 'props' is NULL, the driver that
  58            registered this device has been unloaded, and if class_get_devdata()
  59            points to something in the body of that driver, it is also invalid. */
  60         struct semaphore sem;
  61         /* If this is NULL, the backing module is unloaded */
  62         struct backlight_properties *props;
  63         /* Serialise access to update_status method */
  64         struct mutex update_lock;
  65         /* The framebuffer notifier block */
  66         struct notifier_block fb_notif;
  67         /* The class device structure */
  68         struct class_device class_dev;
  69 };
  70
  71 static inline void backlight_update_status(struct backlight_device *bd)
  72 {
  73         mutex_lock(&bd->update_lock);
  74         if (bd->props && bd->props->update_status)
  75                 bd->props->update_status(bd);
  76         mutex_unlock(&bd->update_lock);
  77 }
  78
  79 extern struct backlight_device *backlight_device_register(const char *name,
  80         struct device *dev,void *devdata,struct backlight_properties *bp);
  81 extern void backlight_device_unregister(struct backlight_device *bd);
  82
  83 #define to_backlight_device(obj) container_of(obj, struct backlight_device, class_dev)
  84
  85 #endif