Re: [patch 5/6] Convert to use mutexes instead of semaphores

From: Dmitry Torokhov
Date: Fri Aug 11 2006 - 10:05:10 EST

On 8/11/06, Michael Hanselmann <linux-kernel@xxxxxxxxx> wrote:
On Fri, Aug 11, 2006 at 09:34:44AM -0400, Dmitry Torokhov wrote:
> How about we add backlight_set_power(&bd, power) to the backlight core
> to take care of proper locking for drivers?

I've tried to add several functions to the backlight core
({s,g}et_{brightness,power}) and they were rejected. Thus all the
locking is spread over the drivers. I agree it's faulty right now.
It's still easier to move to backlight core functions than to fix all
the drivers.

Because I am responsible/wrote for the broken code, how should I

Well, I was reading some more of the drivers and I am also not sure if
such methods are needed in backlight core. Let's take atyfb_base.c -
it tries to manipulate backlight's power from atyfb_blank. But it is
normally called from fb_blank() which is then calls
fb_notifier_call_chain(FB_EVENT_BLANK, &event);
So on the end backlight device will get that event and will turn off
power anyway. Now, atyfb_blank is also called suring suspend/resume so
we probably should just add handling of FB_EVENT_SUSPEND and
FB_EVENT_RESUME to the backlight core.


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