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From:   ChiaEn Wu <peterwu.pub@gmail.com>
Date:   Thu, 14 Jul 2022 15:13:19 +0800
Message-ID: <CABtFH5LT1Ct_9-B_XRrGwYFmL5kGS6KHR7dNVyUO5z4sTy_6oA@mail.gmail.com>
Subject: Re: [PATCH v4 13/13] video: backlight: mt6370: Add Mediatek MT6370 support
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     Lee Jones <lee.jones@linaro.org>,
        Daniel Thompson <daniel.thompson@linaro.org>,
        Jingoo Han <jingoohan1@gmail.com>, Pavel Machek <pavel@ucw.cz>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        Sebastian Reichel <sre@kernel.org>,
        Chunfeng Yun <chunfeng.yun@mediatek.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Jonathan Cameron <jic23@kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Guenter Roeck <linux@roeck-us.net>,
        "Krogerus, Heikki" <heikki.krogerus@linux.intel.com>,
        Helge Deller <deller@gmx.de>,
        ChiaEn Wu <chiaen_wu@richtek.com>,
        Alice Chen <alice_chen@richtek.com>,
        cy_huang <cy_huang@richtek.com>,
        dri-devel <dri-devel@lists.freedesktop.org>,
        Linux LED Subsystem <linux-leds@vger.kernel.org>,
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Andy Shevchenko <andy.shevchenko@gmail.com> =E6=96=BC 2022=E5=B9=B47=E6=9C=
=8813=E6=97=A5 =E9=80=B1=E4=B8=89 =E6=99=9A=E4=B8=8A8:07=E5=AF=AB=E9=81=93=
=EF=BC=9A
>
> On Wed, Jul 13, 2022 at 12:53 PM ChiaEn Wu <peterwu.pub@gmail.com> wrote:
> > Andy Shevchenko <andy.shevchenko@gmail.com> =E6=96=BC 2022=E5=B9=B47=E6=
=9C=885=E6=97=A5 =E9=80=B1=E4=BA=8C =E6=B8=85=E6=99=A85:14=E5=AF=AB=E9=81=
=93=EF=BC=9A
> > > On Mon, Jul 4, 2022 at 7:43 AM ChiaEn Wu <peterwu.pub@gmail.com> wrot=
e:
>
> Please, remove unneeded context when replying!
>
> ...
>
> > > > +               brightness_val[0] =3D (brightness - 1) & MT6370_BL_=
DIM2_MASK;
> > > > +               brightness_val[1] =3D (brightness - 1)
> > > > +                                   >> fls(MT6370_BL_DIM2_MASK);
> > >
> > > Bad indentation. One line?
> >
> > Well... if indent to one line, it will be over 80 characters(or called =
columns?)
> > From my understanding, it is not allowed, right??
>
> It's allowed to some extent.Use your common sense.
> Here it's obviously broken indentation.
>
> ...
>
> > > > +               prop_val =3D (ilog2(roundup_pow_of_two(prop_val)) +=
 1) >> 1;
> > >
> > > Isn't something closer to get_order() or fls()?
> >
> > I will revise it to "(get_order(prop_va * PAGE_SIZE) + 1) / 2" and
> > this change is meet your expectations??
>
> Nope. Try again. What about fls()?

I have tried two methods so far, as follows
-------------------------------------------------------------
/*
 * prop_val =3D  1      -->  1 steps --> b'00
 * prop_val =3D  2 ~  4 -->  4 steps --> b'01
 * prop_val =3D  5 ~ 16 --> 16 steps --> b'10
 * prop_val =3D 17 ~ 64 --> 64 steps --> b'11
*/

// 1. use fls() and ffs() combination
prop_val =3D ffs(prop_val) =3D=3D fls(prop_val) ? fls(prop_val) >> 1 :
(fls(prop_val) + 1) >> 1;

// 2. use one line for-loop, but without fls()
for (i =3D --prop_val, prop_val =3D 0; i >> 2 * prop_val !=3D 0; prop_val++=
);
-------------------------------------------------------------
Do these changes meet your expectations??

>
> ...
>
> > > > +       props->max_brightness =3D min_t(u32, brightness,
> > > > +                                     MT6370_BL_MAX_BRIGHTNESS);
> > >
> > > One line?
> >
> >  Ditto, it will be over 80 characters...
>
> As per above.
>
> --
> With Best Regards,
> Andy Shevchenko