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>
diff --git a/drivers/video/backlight/lcd.c b/drivers/video/backlight/lcd.c
index 9590248..1e1e61a 100644
--- a/drivers/video/backlight/lcd.c
+++ b/drivers/video/backlight/lcd.c
@@ -198,6 +198,7 @@
return ERR_PTR(-ENOMEM);
init_MUTEX(&new_ld->sem);
+ mutex_init(&new_ld->update_lock);
new_ld->props = lp;
memset(&new_ld->class_dev, 0, sizeof(new_ld->class_dev));
new_ld->class_dev.class = &lcd_class;