linux-kernel - Re: [PATCH v4 2/2] iio: proximity: Add driver support for vcnl3020 proximity sensor

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Message-ID: <CAHp75Vfo18+PD8N1WaonLDHv=QLOdb6xpD_grVVj02L=GtqNDA@mail.gmail.com>
Date:   Sat, 28 Mar 2020 20:56:39 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Jonathan Cameron <jic23@...nel.org>
Cc:     Ivan Mikhaylov <i.mikhaylov@...ro.com>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio <linux-iio@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v4 2/2] iio: proximity: Add driver support for vcnl3020
 proximity sensor

On Sat, Mar 28, 2020 at 5:11 PM Jonathan Cameron <jic23@...nel.org> wrote:
> On Fri, 27 Mar 2020 13:49:54 +0300
> Ivan Mikhaylov <i.mikhaylov@...ro.com> wrote:

...

> > Datasheet: http://www.vishay.com/docs/84150/vcnl3020.pdf
> > Signed-off-by: Ivan Mikhaylov <i.mikhaylov@...ro.com>
> A few things inline.
>
> I note Andy suggested a Datasheet tag, but has it actually been
> standardised?

I don't think so, but I bet it's a good idea to have it.

...

> > +     rc = device_property_read_u32(data->dev, "led-current", &led_current);
>
> The presence of a firmware read (dt / acpi etc) means that the i2c id table
> isn't actually useful for probing.

...in case if there are no defaults hard coded in the driver.

> > +     if (rc) {
> > +             dev_err(data->dev, "Couldn't get led current (%d)", rc);
> > +             return rc;
> > +     }

...

> > +     rc = regmap_read(data->regmap, VCNL_PS_RESULT_HI, &hi);
> > +     if (rc)
> > +             goto err_unlock;
> > +     dev_dbg(data->dev, "result high byte 0x%x", hi);
> > +
> > +     rc = regmap_read(data->regmap, VCNL_PS_RESULT_LO, &lo);
> > +     if (rc)
> > +             goto err_unlock;
>
> These are neigbouring registers.  Can you not get away with a bulk read?
> The datasheet suggests the device does auto address incrementing.
>
> If you do that, you can read directly into an __be16/__le16 (I haven't
> checked which) and do an endian conversion to whatever the cpu is
> using.

Oh, indeed. How I missed this during my review? :-)

-- 
With Best Regards,
Andy Shevchenko