Re: [PATCH] Enable backlight when trigger is activated

From: Pavel Machek <pavel@ucw.cz>
To: Ezequiel Garcia <ezequiel@collabora.com>
Cc: kernel list <linux-kernel@vger.kernel.org>,
	linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
	linux-omap@vger.kernel.org, tony@atomide.com, sre@kernel.org,
	nekit1000@gmail.com, mpartap@gmx.net, merlijn@wizzup.org,
	jacek.anaszewski@gmail.com, linux-leds@vger.kernel.org,
	b.zolnierkie@samsung.com, dri-devel@lists.freedesktop.org,
	linux-fbdev@vger.kernel.org
Subject: Re: [PATCH] Enable backlight when trigger is activated
Date: Mon, 22 Jul 2019 09:50:32 +0200	[thread overview]
Message-ID: <20190722075032.GA27524@amd> (raw)
In-Reply-To: <22d7eca4ad8aa2e73933c4f83c92221ce6e0945a.camel@collabora.com>

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Hi!

> > Configuring backlight trigger from dts results in backlight off during
> > boot. Machine looks dead upon boot, which is not good.
> > 
> > Fix that by enabling LED on trigger activation.

> > +++ b/drivers/leds/trigger/ledtrig-backlight.c
> > @@ -114,6 +114,8 @@ static int bl_trig_activate(struct led_classdev *led)
> >  	n->old_status = UNBLANK;
> >  	n->notifier.notifier_call = fb_notifier_callback;
> >  
> > +	led_set_brightness(led, LED_ON);
> > +
> 
> This looks fishy.
> 
> Maybe you should use a default-state = "keep" instead? (and you'll have
> to support it in the LED driver).
> 
> That'll give you proper "don't touch the LED if it was turned on" behavior,
> which is what you seem to want.

Actually no, that's not what I want. LED should go on if the display
is active, as soon as trigger is activated.

Unfortunately, I have see no good way to tell if the display is
active (and display is usually active when trigger is activated).

Thanks,
									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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