linux-kernel - Re: [PATCH v3 1/2] dt: bindings: lm3692x: Add bindings for lm3692x LED driver

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Message-ID: <17b8e1ce-092a-0449-4733-533162b26499@ti.com>
Date:   Fri, 17 Nov 2017 12:02:39 -0600
From:   Dan Murphy <dmurphy@...com>
To:     Jingoo Han <jingoohan1@...il.com>, "'Pavel Machek'" <pavel@....cz>
CC:     "'Jacek Anaszewski'" <jacek.anaszewski@...il.com>,
        <robh+dt@...nel.org>, <mark.rutland@....com>, <rpurdie@...ys.net>,
        <devicetree@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        <linux-leds@...r.kernel.org>, "'Lee Jones'" <lee.jones@...aro.org>,
        "'Daniel Thompson'" <daniel.thompson@...aro.org>
Subject: Re: [PATCH v3 1/2] dt: bindings: lm3692x: Add bindings for lm3692x
 LED driver

Pavel and Jacek

On 11/17/2017 10:30 AM, Jingoo Han wrote:
> On Friday, November 17, 2017 6:21 AM, Pavel Machek wrote:
>>
>> Hi!
>>
>>>>> If that does not yet exist... you want to create glue layer to be
>> able
>>>>> to use LED as a display backlight. (It may already exist, no idea).
>>>>>
>>>>> ...
>>>>>
>>>>> Actually or maybe a LED trigger. Just set LED's trigger to "this is
>>>>> display backlight".
>>>>
>>>> There is one already:
>>>>
>>>> drivers/leds/trigger/ledtrig-backlight.c
>>>>
>>>> It adds a LED class device to the fb_notifier_list
>>>> (drivers/video/fbdev/core/fb_notify.c)
>>>>
>>>> using fb_register_client(). The same is used in
>>>> backlight_device_register (drivers/video/backlight/backlight.c).
>>>>
>>>> Actually why do you want to have this driver in the LED subsystem,
>>>> if it is advertised as "designed for LCD display backlighting"?
>>>
>>> Well this is also advertised as a driver for Smart phone and tablet
>> devices.  And having worked with the Android lighting
>>> solutions this is the preferred subsystem for Android.  The Android OS
>> manages the led brightness based on ALS values and in
>>> turn calls into the driver to control the brightness register through
>> the vendor provided lighting HAL.
>>>
>>
>> Well.. if it can control other LEDs than just backlight, I believe it
>> can stay in the LED subsystem.
> 
> I also agree with your opinion.

I will make the necessary changes for v4.

Just a heads up I won't be posting v4 until after the US holiday so you
don't think I abandoned everything.

Dan

> 
> Best regards,
> Jingoo Han
> 
>>
>>> I am going to look at the backlight source to figure out how to get the
>> same functionality using the backlight subsystem.
>>> Otherwise I will plug in this driver to the backlight subsystem through
>> the notifier.
>>>
>>
>> The backlight trigger should be ok.
>>
>> Best regards,
>>
> Pavel
>> --
>> (english) http://www.livejournal.com/~pavelmachek
>> (cesky, pictures)
>> http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
> 


-- 
------------------
Dan Murphy