include/linux/lcd.h

   1 /*
   2  * LCD Lowlevel Control Abstraction
   3  *
   4  * Copyright (C) 2003,2004 Hewlett-Packard Company
   5  *
   6  */
   7
   8 #ifndef _LINUX_LCD_H
   9 #define _LINUX_LCD_H
  10
  11 #include <linux/device.h>
  12 #include <linux/mutex.h>
  13 #include <linux/notifier.h>
  14
  15 /* Notes on locking:
  16  *
  17  * lcd_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 set_power() 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_power() 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 lcd_device;
  31 struct fb_info;
  32
  33 /* This structure defines all the properties of a LCD flat panel. */
  34 struct lcd_properties {
  35         /* Get the LCD panel power status (0: full on, 1..3: controller
  36            power on, flat panel power off, 4: full off), see FB_BLANK_XXX */
  37         int (*get_power)(struct lcd_device *);
  38         /* Enable or disable power to the LCD (0: on; 4: off, see FB_BLANK_XXX) */
  39         int (*set_power)(struct lcd_device *, int power);
  40         /* The maximum value for contrast (read-only) */
  41         int max_contrast;
  42         /* Get the current contrast setting (0-max_contrast) */
  43         int (*get_contrast)(struct lcd_device *);
  44         /* Set LCD panel contrast */
  45         int (*set_contrast)(struct lcd_device *, int contrast);
  46         /* Check if given framebuffer device is the one LCD is bound to;
  47            return 0 if not, !=0 if it is. If NULL, lcd always matches the fb. */
  48         int (*check_fb)(struct fb_info *);
  49 };
  50
  51 struct lcd_device {
  52         /* This protects the 'props' field. If 'props' is NULL, the driver that
  53            registered this device has been unloaded, and if class_get_devdata()
  54            points to something in the body of that driver, it is also invalid. */
  55         struct semaphore sem;
  56         /* If this is NULL, the backing module is unloaded */
  57         struct lcd_properties *props;
  58         /* Serialise access to set_power method */
  59         struct mutex update_lock;
  60         /* The framebuffer notifier block */
  61         struct notifier_block fb_notif;
  62         /* The class device structure */
  63         struct class_device class_dev;
  64 };
  65
  66 static inline void lcd_set_power(struct lcd_device *ld, int power)
  67 {
  68         mutex_lock(&ld->update_lock);
  69         if (ld->props && ld->props->set_power)
  70                 ld->props->set_power(ld, power);
  71         mutex_unlock(&ld->update_lock);
  72 }
  73
  74 extern struct lcd_device *lcd_device_register(const char *name,
  75         void *devdata, struct lcd_properties *lp);
  76 extern void lcd_device_unregister(struct lcd_device *ld);
  77
  78 #define to_lcd_device(obj) container_of(obj, struct lcd_device, class_dev)
  79
  80 #endif