Merge branch 'master' of /pub/scm/linux/kernel/git/torvalds/linux-2.6

[karo-tx-linux.git] / include / linux / backlight.h

diff --git a/include/linux/backlight.h b/include/linux/backlight.h
index 75e91f5b6a04ce7dc0626599d9d21ac08f8b3059..1023ba0d6e5541aadfbca392ef42cc68a94a9acd 100644 (file)
--- 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,
-       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)