linux-kernel - Re: [RFC] User-defined leds

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Message-ID: <20160805195130.GA26694@amd>
Date:	Fri, 5 Aug 2016 21:51:31 +0200
From:	Pavel Machek <pavel@....cz>
To:	Marcel Holtmann <marcel@...tmann.org>
Cc:	David Lechner <david@...hnology.com>, linux-leds@...r.kernel.org,
	Richard Purdie <rpurdie@...ys.net>,
	Jacek Anaszewski <j.anaszewski@...sung.com>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Joel Becker <jlbec@...lplan.org>
Subject: Re: [RFC] User-defined leds

Hi!

> > short version: I have a use case for leds where I want to be able to use the triggers in the leds subsystem without having a physical hardware led.
> > 
> > long version: I am working on a program to make one embedded system (http://fatcatlab.com/product/evb/) compatible with another (http://mindstorms.lego.com). One has physical red/green LEDs, that use the gpio leds driver to control them. The other system does not have physical leds. However, it does have a color screen. So, my idea is
> > to create virtual LEDs on the screen that emulate the physical LEDs on the other device.
> > 
> > I would like to make a userspace program that works the same on both devices. If the leds were simple on-off, then it would of course be simpler to make the virtual leds completely in userspace. However, we are currently using other triggers (disk activity/heatbeat/etc.) with the leds. I would like for the virtual LEDs to be able to use these triggers as well.
> 
> this is funny since I have just written a ledsim.c using debugfs to emulate a LED and read out its state via a simple cat command. I found that useful for testing triggers in the Bluetooth subsystem and see if they behave correctly without bothering to run this on real hardware.
> 

Could the device tree be used to bind LED driver to otherwise unused
gpio?

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