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

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Date:   Fri, 6 Apr 2018 16:54:39 +0100
From:   Daniel Thompson <daniel.thompson@...aro.org>
To:     Enric Balletbo Serra <eballetbo@...il.com>
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

On Tue, Mar 20, 2018 at 01:13:20PM +0100, Enric Balletbo Serra wrote:
> 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.

You weren't missing anything... and I've just dived through my mail
history and retrieved the patchset so I can review it.

You should now have an ack from me on every patch. Sorry it has taken 
so long.


Daniel.


> 
> 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
> >> >