linux-kernel - Re: [PATCH v4 13/13] video: backlight: mt6370: Add Mediatek MT6370 support

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Message-ID: <CABtFH5K-2+2hbpvpq2nPE5AsznkQxZF2r3MVC64Q39DJhVuUtA@mail.gmail.com>
Date:   Wed, 13 Jul 2022 18:53:26 +0800
From:   ChiaEn Wu <peterwu.pub@...il.com>
To:     Andy Shevchenko <andy.shevchenko@...il.com>
Cc:     Lee Jones <lee.jones@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>, Pavel Machek <pavel@....cz>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Matthias Brugger <matthias.bgg@...il.com>,
        Sebastian Reichel <sre@...nel.org>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Guenter Roeck <linux@...ck-us.net>,
        "Krogerus, Heikki" <heikki.krogerus@...ux.intel.com>,
        Helge Deller <deller@....de>,
        ChiaEn Wu <chiaen_wu@...htek.com>,
        Alice Chen <alice_chen@...htek.com>,
        cy_huang <cy_huang@...htek.com>,
        dri-devel <dri-devel@...ts.freedesktop.org>,
        Linux LED Subsystem <linux-leds@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        linux-arm Mailing List <linux-arm-kernel@...ts.infradead.org>,
        "moderated list:ARM/Mediatek SoC support" 
        <linux-mediatek@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        USB <linux-usb@...r.kernel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        "open list:FRAMEBUFFER LAYER" <linux-fbdev@...r.kernel.org>,
        szuni chen <szunichen@...il.com>
Subject: Re: [PATCH v4 13/13] video: backlight: mt6370: Add Mediatek MT6370 support

Hi Andy,
Thanks for your reply! I have some questions want to ask you below.

Andy Shevchenko <andy.shevchenko@...il.com> 於 2022年7月5日 週二 清晨5:14寫道：
>
> On Mon, Jul 4, 2022 at 7:43 AM ChiaEn Wu <peterwu.pub@...il.com> wrote:
> >
> > From: ChiaEn Wu <chiaen_wu@...htek.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] = (brightness - 1) & MT6370_BL_DIM2_MASK;
> > +               brightness_val[1] = (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??

>
> ...
>
> > +       if (priv->enable_gpio)
>
> Dup check.
>
> > +               gpiod_set_value(priv->enable_gpio, brightness ? 1 : 0);
>
> ...
>
> > +       brightness = brightness_val[1] << fls(MT6370_BL_DIM2_MASK);
> > +       brightness += (brightness_val[0] & MT6370_BL_DIM2_MASK);
>
> Too many parentheses.
>
> ...
>
> > +               /*
> > +                * prop_val =  1      -->  1 steps --> 0x00
> > +                * prop_val =  2 ~  4 -->  4 steps --> 0x01
> > +                * prop_val =  5 ~ 16 --> 16 steps --> 0x10
> > +                * prop_val = 17 ~ 64 --> 64 steps --> 0x11
> > +                */
> > +               prop_val = (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 = min_t(u32, brightness,
> > +                                     MT6370_BL_MAX_BRIGHTNESS);
>
> One line?

 Ditto, it will be over 80 characters...

>
> ...
>
> > +       val = 0;
>
> Do you need this here?
>
> > +       prop_val = 0;
>
> Useless.
>
> > +       ret = device_property_read_u8(dev, "mediatek,bled-channel-use",
> > +                                     &prop_val);
> > +       if (ret) {
> > +               dev_err(dev, "mediatek,bled-channel-use DT property missing\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 = {
> > +               .type = BACKLIGHT_RAW,
> > +               .scale = BACKLIGHT_SCALE_LINEAR,
> > +       };
> > +       int ret;
>
>   struct device *dev = &pdev->dev;
>
> will save you a few LoCs.
>
> --
> With Best Regards,
> Andy Shevchenko

Best regards,
ChiaEn Wu