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;
 }