linux-kernel - Re: Camera LED on Librem 5 was Re: [PATCH] backlight: add led-backlight driver

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Message-ID: <20200814172320.GA740513@bogon.m.sigxcpu.org>
Date:   Fri, 14 Aug 2020 19:23:20 +0200
From:   Guido Günther <agx@...xcpu.org>
To:     Pavel Machek <pavel@....cz>
Cc:     kernel list <linux-kernel@...r.kernel.org>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>
Subject: Re: Camera LED on Librem 5 was Re: [PATCH] backlight: add
 led-backlight driver

Hi Pavel,
On Fri, Feb 21, 2020 at 12:41:51AM +0100, Pavel Machek wrote:
> Hi!
> 
> > > This patch adds a led-backlight driver (led_bl), which is similar to
> > > pwm_bl except the driver uses a LED class driver to adjust the
> > > brightness in the HW. Multiple LEDs can be used for a single backlight.
> > 
> > Tested-by: Guido Günther <agx@...xcpu.org>
> 
> Thanks for testing!
> 
> I noticed blog post about using Librem 5 torch. Unfortunately, it used
> very strange/non-standard interface, first using LED as a GPIO to
> enable LED controller, then direct i2c access. That is not acceptable
> interface for mainline, and it would be better not to advertise such
> code, as it will likely become broken in future.

I agree, there's a driver for the lm3560 in media/ but how would one
expose the torch part as a LED? It seems you hit something similar in

    https://lkml.org/lkml/2018/5/6/30

I also couldn't find an in tree driver that registers a flashlight
as a v4l subdev. Did i miss that?

Cheers,
 -- Guido