diff options
Diffstat (limited to 'include/linux/backlight.h')
| -rw-r--r-- | include/linux/backlight.h | 50 |
1 files changed, 39 insertions, 11 deletions
diff --git a/include/linux/backlight.h b/include/linux/backlight.h index a5cf1beacb44..1023ba0d6e55 100644 --- a/include/linux/backlight.h +++ b/include/linux/backlight.h @@ -9,17 +9,28 @@ #define _LINUX_BACKLIGHT_H #include <linux/device.h> +#include <linux/mutex.h> #include <linux/notifier.h> +/* Notes on locking: + * + * backlight_device->ops_lock is an internal backlight lock protecting the + * ops pointer and no code outside the core should need to touch it. + * + * Access to update_status() is serialised by the update_lock mutex since + * most drivers seem to need this and historically get it wrong. + * + * Most drivers don't need locking on their get_brightness() method. + * If yours does, you need to implement it in the driver. You can use the + * update_lock mutex if appropriate. + * + * Any other use of the locks below is probably wrong. + */ + struct backlight_device; struct fb_info; -/* This structure defines all the properties of a backlight - (usually attached to a LCD). */ -struct backlight_properties { - /* Owner module */ - struct module *owner; - +struct backlight_ops { /* Notify the backlight driver some property has changed */ int (*update_status)(struct backlight_device *); /* Return the current backlight brightness (accounting for power, @@ -28,7 +39,10 @@ struct backlight_properties { /* Check if given framebuffer device is the one bound to this backlight; return 0 if not, !=0 if it is. If NULL, backlight always matches the fb. */ int (*check_fb)(struct fb_info *); +}; +/* This structure defines all the properties of a backlight */ +struct backlight_properties { /* Current User requested brightness (0 - max_brightness) */ int brightness; /* Maximal value for brightness (read-only) */ @@ -41,20 +55,34 @@ struct backlight_properties { }; struct backlight_device { - /* This protects the 'props' field. If 'props' is NULL, the driver that + /* Backlight properties */ + struct backlight_properties props; + + /* Serialise access to update_status method */ + struct mutex update_lock; + + /* This protects the 'ops' field. If 'ops' is NULL, the driver that registered this device has been unloaded, and if class_get_devdata() points to something in the body of that driver, it is also invalid. */ - struct semaphore sem; - /* If this is NULL, the backing module is unloaded */ - struct backlight_properties *props; + struct mutex ops_lock; + struct backlight_ops *ops; + /* The framebuffer notifier block */ struct notifier_block fb_notif; /* The class device structure */ struct class_device class_dev; }; +static inline void backlight_update_status(struct backlight_device *bd) +{ + mutex_lock(&bd->update_lock); + if (bd->ops && bd->ops->update_status) + bd->ops->update_status(bd); + mutex_unlock(&bd->update_lock); +} + extern struct backlight_device *backlight_device_register(const char *name, - struct device *dev,void *devdata,struct backlight_properties *bp); + struct device *dev, void *devdata, struct backlight_ops *ops); extern void backlight_device_unregister(struct backlight_device *bd); #define to_backlight_device(obj) container_of(obj, struct backlight_device, class_dev) |