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From:   ChiaEn Wu <peterwu.pub@gmail.com>
Date:   Wed, 13 Jul 2022 18:53:26 +0800
Message-ID: <CABtFH5K-2+2hbpvpq2nPE5AsznkQxZF2r3MVC64Q39DJhVuUtA@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>,
        devicetree <devicetree@vger.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@lists.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@lists.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Linux PM <linux-pm@vger.kernel.org>,
        USB <linux-usb@vger.kernel.org>,
        linux-iio <linux-iio@vger.kernel.org>,
        "open list:FRAMEBUFFER LAYER" <linux-fbdev@vger.kernel.org>,
        szuni chen <szunichen@gmail.com>
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Hi Andy,
Thanks for your reply! I have some questions want to ask you below.

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> wrote:
> >
> > From: ChiaEn Wu <chiaen_wu@richtek.com>
> >
> > Add Mediatek MT6370 Backlight support.
>
> ...
>
> > +         This driver can also be built as a module. If so the module
>
> If so,
>
> > +         will be called "mt6370-backlight.ko".
>
> No ".ko" part.
>
> ...
>
> > +#include <linux/gpio/driver.h>
>
> Can you elaborate on this?
>
> > +#include <linux/kernel.h>
> > +#include <linux/log2.h>
> > +#include <linux/minmax.h>
> > +#include <linux/module.h>
>
> > +#include <linux/of.h>
>
> Can you elaborate on this?
>
> > +#include <linux/platform_device.h>
> > +#include <linux/regmap.h>
>
> Missed mod_devicetable.h.
>
> ...
>
> > +               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 colu=
mns?)
From my understanding, it is not allowed, right??

>
> ...
>
> > +       if (priv->enable_gpio)
>
> Dup check.
>
> > +               gpiod_set_value(priv->enable_gpio, brightness ? 1 : 0);
>
> ...
>
> > +       brightness =3D brightness_val[1] << fls(MT6370_BL_DIM2_MASK);
> > +       brightness +=3D (brightness_val[0] & MT6370_BL_DIM2_MASK);
>
> Too many parentheses.
>
> ...
>
> > +               /*
> > +                * prop_val =3D  1      -->  1 steps --> 0x00
> > +                * prop_val =3D  2 ~  4 -->  4 steps --> 0x01
> > +                * prop_val =3D  5 ~ 16 --> 16 steps --> 0x10
> > +                * prop_val =3D 17 ~ 64 --> 64 steps --> 0x11
> > +                */
> > +               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??

>
> ...
>
> > +       props->max_brightness =3D min_t(u32, brightness,
> > +                                     MT6370_BL_MAX_BRIGHTNESS);
>
> One line?

 Ditto, it will be over 80 characters...

>
> ...
>
> > +       val =3D 0;
>
> Do you need this here?
>
> > +       prop_val =3D 0;
>
> Useless.
>
> > +       ret =3D device_property_read_u8(dev, "mediatek,bled-channel-use=
",
> > +                                     &prop_val);
> > +       if (ret) {
> > +               dev_err(dev, "mediatek,bled-channel-use DT property mis=
sing\n");
> > +               return ret;
> > +       }
> > +
> > +       if (!prop_val || prop_val > MT6370_BL_MAX_CH) {
> > +               dev_err(dev,
> > +                       "No channel specified or over than upper bound =
(%d)\n",
> > +                       prop_val);
> > +               return -EINVAL;
> > +       }
>
> ...
>
> > +static int mt6370_bl_probe(struct platform_device *pdev)
> > +{
> > +       struct mt6370_priv *priv;
> > +       struct backlight_properties props =3D {
> > +               .type =3D BACKLIGHT_RAW,
> > +               .scale =3D BACKLIGHT_SCALE_LINEAR,
> > +       };
> > +       int ret;
>
>   struct device *dev =3D &pdev->dev;
>
> will save you a few LoCs.
>
> --
> With Best Regards,
> Andy Shevchenko

Best regards,
ChiaEn Wu