linux-kernel - Re: led: hw-trigger, global brightness and multi-colored leds

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Date:   Wed, 2 May 2018 23:21:05 +0200
From:   Pavel Machek <pavel@....cz>
To:     Uwe Kleine-König <uwe@...ine-koenig.org>
Cc:     Jacek Anaszewski <jacek.anaszewski@...il.com>,
        linux-kernel@...r.kernel.org,
        Tomas Hlavacek <tomas.hlavacek@....cz>
Subject: Re: led: hw-trigger, global brightness and multi-colored leds

Hi!

> on the Turris Omnia[1] the LEDs are controllable via an i2c device. Each
> LED can be either in "manual mode" or in a mode I'd call "native mode"
> which is the default. In this native mode the LED being on or off
> depends on an input line that is controlled by another hardware. So a
> LED signals for example activity on the WAN ethernet port without any
> software intervention, but can be used as a normal LED, too, when in
> "manual mode" where it can be switched on and off by a register
> write.

"Native mode" is quite common. We have it for example on Nokia N900
here (charger has hw option to automatically control the LED).

I believe reasonable solution would be to have "hardware" trigger, and
have it selected by default. When active, LED would be controlled by
hardware.

> Another feature of the LED device is that there is a global brightness
> register that influences all LED's brightness (if on) independent of the
> operating mode.

We can't describe that easily.

> Further the color of each LED can be set to an RGB triplet.

We normally handle RGB LED as three independend LEDs, like
notify::red, notify::green, notify::blue. Again, example is Nokia N900
or Motorola Droid 4.

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

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