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From:   ChiYuan Huang <u0084500@gmail.com>
Date:   Sat, 18 Jun 2022 23:16:44 +0800
Message-ID: <CADiBU3-wO0-0c9y-GpE15ra2AqkAG-ftqTh+hCvYEY-TojZ-pg@mail.gmail.com>
Subject: Re: [PATCH 2/2] iio: adc: Add rtq6056 support
To:     Andy Shevchenko <andy.shevchenko@gmail.com>
Cc:     Jonathan Cameron <jic23@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        cy_huang <cy_huang@richtek.com>,
        linux-iio <linux-iio@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        devicetree <devicetree@vger.kernel.org>
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Andy Shevchenko <andy.shevchenko@gmail.com> =E6=96=BC 2022=E5=B9=B46=E6=9C=
=8818=E6=97=A5 =E9=80=B1=E5=85=AD =E5=87=8C=E6=99=A81:08=E5=AF=AB=E9=81=93=
=EF=BC=9A
>
> On Fri, Jun 17, 2022 at 11:37 AM cy_huang <u0084500@gmail.com> wrote:
> >
> > From: ChiYuan Huang <cy_huang@richtek.com>
> >
> > Add Richtek RTQ6056 supporting.
> >
> > It can be used for the system to monitor load current and power with 16=
bit
>
> 16-bit
>
Ack in next.
> > resolution.
>
> Overall looks good, needs some cosmetic work.
>
> ...
>
> > +KernelVersion: 5.18.2
>
> Wrong version, this won't be part of a stable kernel.
>
From kernel.org, currently the stable kernel version is 5.18.5.
Change to 5.18.5?
> ...
>
> > +#include <linux/of.h>
>
> Any users of this?
>
function 'of_property_read_u32'.
But from Jonathan's reply, I may change it to 'device_property_read_u32'.
And also property.h will be included.
> But for sure you missed
>
>   mod_devicetable.h
>   types.h
>
Ack in next. But for types.h, i2c.h already include device.h.
And device.h already include types.h.
Is it still needed to declare explicitly for types.h??
> ...
>
> > +#define RTQ6056_DEFAULT_RSHUNT 2000
>
> _mOHMs ?
>
From Jonathan's reply, I may remove this value defined.
Since it's already a straight value. To define it, seems to decrease
the readability.
> ...
>
> > +enum {
> > +       F_OPMODE =3D 0, F_VSHUNTCT, F_VBUSCT, F_AVG, F_RESET,
> > +       F_MAX_FIELDS
>
> Hard to read this way. Split to be one emum entry per line.
>
Ack in next.
> > +};
>
> ...
>
> > +struct rtq6056_priv {
> > +       struct device *dev;
> > +       struct regmap *regmap;
>
> Swapping these two might give less code in the generated binary. Have
> you run bloat-o-meter?
>
I never know about this tool.
I'll check it before I submit the next revision.
Thanks for the reminding.

But from Jonathan's reply, I may remove 'struct regmap *regmap'.
If all function need the 'regmap', a local variable 'regmap' need to
be declared.
To use struct regmap *regmap =3D dev_get_regmap(dev, NULL) is more effectiv=
e.
> > +       struct regmap_field *rm_fields[F_MAX_FIELDS];
> > +       u32 shunt_resistor_uohm;
> > +       int vshuntct; /* vshunt conversion time in uS */
> > +       int vbusct; /* vbus conversion time in uS */
> > +       int avg_sample;
> > +};
>
> ...
>
> > +       IIO_CHAN_SOFT_TIMESTAMP(RTQ6056_MAX_CHANNEL)
>
> Keep a comma.
>
Ack in next
> ...
>
>
> > +       /* Only power and vbus channel is unsigned */
> > +       if (channel =3D=3D RTQ6056_CH_VBUS || channel =3D=3D RTQ6056_CH=
_POWER)
> > +               *val =3D regval;
> > +       else
>
> > +               *val =3D (s16)regval;
>
> Why casting? At very minimum this requires a comment.
The value is already the 16-bit 2's complement value. That's why the
casting is here.
From Jonathan's reply, will replace it by sign_extend32.
>
> ...
>
> > +       if (val > 8205 || val < 139)
> > +               return -EINVAL;
>
> This strange range requires a good comment with possible references to
> the datasheet.
>
Ack in next.
> ...
>
> > +static const int rtq6056_avg_sample_list[] =3D {
> > +       1, 4, 16, 64, 128, 256, 512, 1024
>
> Keep a comma at the end.
>
> > +};
>
> ...
>
> > +static int rtq6056_adc_read_label(struct iio_dev *indio_dev,
> > +                                 struct iio_chan_spec const *chan,
> > +                                 char *label)
> > +{
> > +       return snprintf(label, PAGE_SIZE, "%s\n",
> > +                       rtq6056_channel_labels[chan->channel]);
>
> sysfs_emit()
>
> > +}
>
> ...
>
> > +static IIO_DEVICE_ATTR(shunt_resistor, 0644,
> > +                      rtq6056_shunt_resistor_show,
> > +                      rtq6056_shunt_resistor_store, 0);
>
> IIO_DEVICE_ATTR_RW()
>
> ...
>
> > +       for_each_set_bit(bit, indio_dev->active_scan_mask,
> > +                        indio_dev->masklength) {
>
> On one line it's better.
>
Ack in next
> > +
>
> Redundant blank line.
>
Ack in next.
> > +               ret =3D regmap_read(priv->regmap, RTQ6056_REG_SHUNTVOLT=
 + bit,
> > +                                 &raw);
> > +               if (ret)
> > +                       goto out;
> > +
> > +               data.vals[i++] =3D raw;
> > +       }
>
> > +       ret =3D of_property_read_u32(i2c->dev.of_node,
> > +                                  "richtek,shunt-resistor-uohm",
> > +                                  &shunt_resistor_uohm);
>
> device_property_read()
>
From you and other's reply, I may refine this part about the resistor parsi=
ng.
> > +       if (ret)
> > +               shunt_resistor_uohm =3D RTQ6056_DEFAULT_RSHUNT;
>
> Can be done without branch
>
OK
> ... =3D DEFAULT;
> device_property_read_u32(...); // no error checking.
>
> ...
>
> > +static int rtq6056_remove(struct i2c_client *i2c)
> > +{
> > +       struct rtq6056_priv *priv =3D i2c_get_clientdata(i2c);
> > +
> > +       /* Config opmode to 'shutdown' mode to minimize quiescient curr=
ent */
>
> quiescent
>
Sorry for the typo
> > +       return regmap_field_write(priv->rm_fields[F_OPMODE], 0);
> > +}
> > +
> > +static void rtq6056_shutdown(struct i2c_client *i2c)
> > +{
> > +       struct rtq6056_priv *priv =3D i2c_get_clientdata(i2c);
> > +
> > +       /* Config opmode to 'shutdown' mode to minimize quiescient curr=
ent */
>
> quiescent
>
Sorry for the typo
> > +       regmap_field_write(priv->rm_fields[F_OPMODE], 0);
> > +}
>
> --
> With Best Regards,
> Andy Shevchenko