linux-kernel - Re: 2.6.21-rc1 dims my LCD

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Date:	Mon, 26 Feb 2007 16:24:47 +0100 (CET)
From:	Jiri Kosina <jikos@...os.cz>
To:	Richard Purdie <rpurdie@...ys.net>
cc:	Henrique de Moraes Holschuh <hmh@....eng.br>,
	linux-kernel@...r.kernel.org
Subject: Re: 2.6.21-rc1 dims my LCD

On Mon, 26 Feb 2007, Richard Purdie wrote:

> Jiri: I've appended a patch that should already be queued, could you
> test and see if it solves the problem.

Thanks. In the meantime I have gone through the code and I can confirm 
that this is the root cause of what I am observing.

Now regarding the patch - at the time when the dim happened previously, 
currently there is a observable blink (after which the brightness is 
correct). I have put some debugging printk() into fb_notifier_callback(), 
and it turns out that on FB_EVENT_CONBLANK, there are two successive calls 
to backlight_update_status(), second immediately following the first one:

Feb 26 15:11:14 thunder kernel: calling backlight_update_status() with bd->props.fb_blank == 1, bd->props.brightness == 0
Feb 26 15:11:14 thunder kernel: calling backlight_update_status() with bd->props.fb_blank == 0, bd->props.brightness == 0

Is this really a right thing to do?

-- 
Jiri Kosina
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