28ee086d5b
backlight_device->sem has a very specific use as documented in the header file. The external users of this are using it for a different reason, to serialise access to the update_status() method. backlight users were supposed to implement their own internal serialisation of update_status() if needed but everyone is doing things differently and incorrectly. Therefore add a global mutex to take care of serialisation for everyone, once and for all. Locking for get_brightness remains optional since most users don't need it. Also update the lcd class in a similar way. Signed-off-by: Richard Purdie <rpurdie@rpsys.net>
85 lines
2.8 KiB
C
85 lines
2.8 KiB
C
/*
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* Backlight Lowlevel Control Abstraction
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*
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* Copyright (C) 2003,2004 Hewlett-Packard Company
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*
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*/
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#ifndef _LINUX_BACKLIGHT_H
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#define _LINUX_BACKLIGHT_H
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#include <linux/device.h>
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#include <linux/mutex.h>
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#include <linux/notifier.h>
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/* Notes on locking:
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*
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* backlight_device->sem is an internal backlight lock protecting the props
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* field and no code outside the core should need to touch it.
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*
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* Access to update_status() is serialised by the update_lock mutex since
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* most drivers seem to need this and historically get it wrong.
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*
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* Most drivers don't need locking on their get_brightness() method.
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* If yours does, you need to implement it in the driver. You can use the
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* update_lock mutex if appropriate.
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*
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* Any other use of the locks below is probably wrong.
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*/
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struct backlight_device;
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struct fb_info;
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/* This structure defines all the properties of a backlight
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(usually attached to a LCD). */
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struct backlight_properties {
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/* Notify the backlight driver some property has changed */
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int (*update_status)(struct backlight_device *);
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/* Return the current backlight brightness (accounting for power,
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fb_blank etc.) */
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int (*get_brightness)(struct backlight_device *);
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/* Check if given framebuffer device is the one bound to this backlight;
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return 0 if not, !=0 if it is. If NULL, backlight always matches the fb. */
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int (*check_fb)(struct fb_info *);
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/* Current User requested brightness (0 - max_brightness) */
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int brightness;
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/* Maximal value for brightness (read-only) */
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int max_brightness;
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/* Current FB Power mode (0: full on, 1..3: power saving
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modes; 4: full off), see FB_BLANK_XXX */
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int power;
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/* FB Blanking active? (values as for power) */
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int fb_blank;
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};
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struct backlight_device {
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/* This protects the 'props' field. If 'props' is NULL, the driver that
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registered this device has been unloaded, and if class_get_devdata()
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points to something in the body of that driver, it is also invalid. */
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struct semaphore sem;
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/* If this is NULL, the backing module is unloaded */
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struct backlight_properties *props;
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/* Serialise access to update_status method */
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struct mutex update_lock;
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/* The framebuffer notifier block */
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struct notifier_block fb_notif;
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/* The class device structure */
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struct class_device class_dev;
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};
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static inline void backlight_update_status(struct backlight_device *bd)
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{
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mutex_lock(&bd->update_lock);
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if (bd->props && bd->props->update_status)
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bd->props->update_status(bd);
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mutex_unlock(&bd->update_lock);
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}
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extern struct backlight_device *backlight_device_register(const char *name,
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struct device *dev,void *devdata,struct backlight_properties *bp);
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extern void backlight_device_unregister(struct backlight_device *bd);
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#define to_backlight_device(obj) container_of(obj, struct backlight_device, class_dev)
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#endif
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