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->ops_lock is an internal backlight lock protecting the ops
  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 struct lcd_properties {
  34         /* The maximum value for contrast (read-only) */
  35         int max_contrast;
  36 };
  37
  38 struct lcd_ops {
  39         /* Get the LCD panel power status (0: full on, 1..3: controller
  40            power on, flat panel power off, 4: full off), see FB_BLANK_XXX */
  41         int (*get_power)(struct lcd_device *);
  42         /* Enable or disable power to the LCD (0: on; 4: off, see FB_BLANK_XXX) */
  43         int (*set_power)(struct lcd_device *, int power);
  44         /* Get the current contrast setting (0-max_contrast) */
  45         int (*get_contrast)(struct lcd_device *);
  46         /* Set LCD panel contrast */
  47         int (*set_contrast)(struct lcd_device *, int contrast);
  48         /* Check if given framebuffer device is the one LCD is bound to;
  49            return 0 if not, !=0 if it is. If NULL, lcd always matches the fb. */
  50         int (*check_fb)(struct fb_info *);
  51 };
  52
  53 struct lcd_device {
  54         struct lcd_properties props;
  55         /* This protects the 'ops' field. If 'ops' is NULL, the driver that
  56            registered this device has been unloaded, and if class_get_devdata()
  57            points to something in the body of that driver, it is also invalid. */
  58         struct mutex ops_lock;
  59         /* If this is NULL, the backing module is unloaded */
  60         struct lcd_ops *ops;
  61         /* Serialise access to set_power method */
  62         struct mutex update_lock;
  63         /* The framebuffer notifier block */
  64         struct notifier_block fb_notif;
  65         /* The class device structure */
  66         struct class_device class_dev;
  67 };
  68
  69 static inline void lcd_set_power(struct lcd_device *ld, int power)
  70 {
  71         mutex_lock(&ld->update_lock);
  72         if (ld->ops && ld->ops->set_power)
  73                 ld->ops->set_power(ld, power);
  74         mutex_unlock(&ld->update_lock);
  75 }
  76
  77 extern struct lcd_device *lcd_device_register(const char *name,
  78         void *devdata, struct lcd_ops *ops);
  79 extern void lcd_device_unregister(struct lcd_device *ld);
  80
  81 #define to_lcd_device(obj) container_of(obj, struct lcd_device, class_dev)
  82
  83 #endif