linux-kernel - Re: [PATCH v3 0/4] backlight: pwm_bl: support linear interpolation and brightness to human eye

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Message-ID: <CAFqH_51E+9L2fuTY7Zo3=B2fUmL=pJtg7wz3GdN5wxhpqV8p0g@mail.gmail.com>
Date:   Tue, 20 Mar 2018 13:13:20 +0100
From:   Enric Balletbo Serra <eballetbo@...il.com>
To:     Daniel Thompson <daniel.thompson@...aro.org>
Cc:     Enric Balletbo i Serra <enric.balletbo@...labora.com>,
        Doug Anderson <dianders@...gle.com>,
        Pavel Machek <pavel@....cz>, Rob Herring <robh+dt@...nel.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Richard Purdie <rpurdie@...ys.net>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Brian Norris <briannorris@...gle.com>,
        Guenter Roeck <groeck@...gle.com>,
        Lee Jones <lee.jones@...aro.org>,
        Alexandru Stan <amstan@...gle.com>, linux-leds@...r.kernel.org,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>, kernel@...labora.com
Subject: Re: [PATCH v3 0/4] backlight: pwm_bl: support linear interpolation
 and brightness to human eye

Hi Daniel,


2018-03-20 12:22 GMT+01:00 Daniel Thompson <daniel.thompson@...aro.org>:
> On Mon, Mar 19, 2018 at 05:04:31PM +0100, Enric Balletbo Serra wrote:
>> Hi Daniel,
>>
>> Gentle ping for this series, there is any possibility you have a
>> chance to review it? Let me know if you want I change something.
>
> I haven't got it in my TODO backlog... which means either I mistakenly
> deleted it when it went through originally or that I deliberately deleted
> it because I thought a v4 was coming along soon.
>
> I could go diving through the archives if I need to but were there other
> pending changes for this patchset?
>

Unless I am missing something there isn't pending changes requested.

1/4 I addressed your latest comments in this version.
2/4 Has been acked by Rob Herring
3/4 I did not receive feedback but iirc we agreed to use a pre-computed table.
4/4 Is already acked by you.

Regards,
 Enric

>
> Daniel.
>
>
>>
>> Thanks,
>>   Enric
>>
>> 2018-02-08 12:30 GMT+01:00 Enric Balletbo i Serra
>> <enric.balletbo@...labora.com>:
>> > Dear all,
>> >
>> > This series is a third patchset integrating the requested changes.
>> >
>> > The first and second patch what tries to solve is the problem of
>> > granularity for high resolution PWMs. The idea is simple interpolate
>> > between 2 brightness values so we can have a high PWM duty cycle (a
>> > 16 bits PWM is up to 65535 possible steps) without having to list
>> > out every possible value in the dts. I think that this patch is
>> > required to not break backward compability, to be more flexible and
>> > also extend the functionality to be able to use high resolution PWM
>> > with enough steps to have a good UI experience in userspace.
>> >
>> > The thirth and fourth patch is a bit more ambicious, the idea is let
>> > decide the driver the brightness-levels required in function of the PWM
>> > resolution. To do this create a brightness-levels table filled with the
>> > CIE 1931 algorithm values to convert brightness to PWM duty cycle.
>> >
>> > More detailed info is available in the commit message of every patch.
>> >
>> > Both functionalities were tested on a Samsung Chromebook Plus (that has
>> > a 16 bits PWM) and a SL50 device (with a 8 bits PWM)
>> >
>> > Waiting for your feedback.
>> >
>> > Best regards,
>> >
>> > Enric Balletbo i Serra (4):
>> >   backlight: pwm_bl: linear interpolation between brightness-levels
>> >   dt-bindings: pwm-backlight: add a num-interpolation-steps property.
>> >   backlight: pwm_bl: compute brightness of LED linearly to human eye.
>> >   dt-bindings: pwm-backlight: move brightness-levels to optional.
>> >
>> >  .../bindings/leds/backlight/pwm-backlight.txt      |  34 ++-
>> >  drivers/video/backlight/pwm_bl.c                   | 232 +++++++++++++++++++--
>> >  2 files changed, 246 insertions(+), 20 deletions(-)
>> >
>> > --
>> > 2.15.1
>> >