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>
81 lines
2.6 KiB
C
81 lines
2.6 KiB
C
/*
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* LCD 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_LCD_H
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#define _LINUX_LCD_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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* lcd_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 set_power() 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_power() 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 lcd_device;
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struct fb_info;
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/* This structure defines all the properties of a LCD flat panel. */
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struct lcd_properties {
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/* Get the LCD panel power status (0: full on, 1..3: controller
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power on, flat panel power off, 4: full off), see FB_BLANK_XXX */
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int (*get_power)(struct lcd_device *);
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/* Enable or disable power to the LCD (0: on; 4: off, see FB_BLANK_XXX) */
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int (*set_power)(struct lcd_device *, int power);
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/* The maximum value for contrast (read-only) */
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int max_contrast;
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/* Get the current contrast setting (0-max_contrast) */
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int (*get_contrast)(struct lcd_device *);
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/* Set LCD panel contrast */
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int (*set_contrast)(struct lcd_device *, int contrast);
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/* Check if given framebuffer device is the one LCD is bound to;
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return 0 if not, !=0 if it is. If NULL, lcd always matches the fb. */
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int (*check_fb)(struct fb_info *);
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};
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struct lcd_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 lcd_properties *props;
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/* Serialise access to set_power 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 lcd_set_power(struct lcd_device *ld, int power)
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{
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mutex_lock(&ld->update_lock);
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if (ld->props && ld->props->set_power)
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ld->props->set_power(ld, power);
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mutex_unlock(&ld->update_lock);
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}
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extern struct lcd_device *lcd_device_register(const char *name,
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void *devdata, struct lcd_properties *lp);
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extern void lcd_device_unregister(struct lcd_device *ld);
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#define to_lcd_device(obj) container_of(obj, struct lcd_device, class_dev)
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#endif
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