backlight: Fix external uses of backlight internal semaphore

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>

1 files changed, 5 insertions, 15 deletions

diff --git a/drivers/misc/asus-laptop.c b/drivers/misc/asus-laptop.c
index d15ee5e34201..7ace5b9a3d28 100644
--- a/drivers/misc/asus-laptop.c
+++ b/drivers/misc/asus-laptop.c
@@ -348,13 +348,8 @@ static void lcd_blank(int blank)
         struct backlight_device *bd = asus_backlight_device;
 
         if (bd) {
-                down(&bd->sem);
-                if (likely(bd->props)) {
-                        bd->props->power = blank;
-                        if (likely(bd->props->update_status))
-                                bd->props->update_status(bd);
-                }
-                up(&bd->sem);
+                bd->props->power = blank;
+                backlight_update_status(bd);
         }
 }
 
@@ -1028,14 +1023,9 @@ static int asus_backlight_init(struct device *dev)
 
                 asus_backlight_device = bd;
 
-                down(&bd->sem);
-                if (likely(bd->props)) {
-                        bd->props->brightness = read_brightness(NULL);
-                        bd->props->power = FB_BLANK_UNBLANK;
-                        if (likely(bd->props->update_status))
-                                bd->props->update_status(bd);
-                }
-                up(&bd->sem);
+                bd->props->brightness = read_brightness(NULL);
+                bd->props->power = FB_BLANK_UNBLANK;
+                backlight_update_status(bd);
         }
         return 0;
 }