linux-kernel - Re: [PATCH v5 2/2] iio: light: as73211: New driver

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Date:   Sun, 2 Aug 2020 21:02:35 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Christian Eggers <ceggers@...i.de>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        linux-iio <linux-iio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 2/2] iio: light: as73211: New driver

On Sun, Aug 2, 2020 at 7:40 PM Christian Eggers <ceggers@...i.de> wrote:
>
> Support for AMS AS73211 JENCOLOR(R) Digital XYZ Sensor.
>
> This driver has no built-in trigger. In order for making triggered
> measurements, an external (software) trigger driver like
> iio-trig-hrtimer or iio-trig-sysfs is required.
>
> The sensor supports single and continuous measurement modes. The latter
> is not used by design as this would require tight timing synchronization
> between hardware and driver without much benefit.

Thanks for an update, my comments below.

> Datasheet: https://ams.com/documents/20143/36005/AS73211_DS000556_3-01.pdf/a65474c0-b302-c2fd-e30a-c98df87616df

Do we need the UUID after the document file name?

...

> +/* Available sample frequencies are 1.024MHz multiplied by powers of two. */
> +static const int as73211_samp_freq_avail[] = {
> +       AS73211_SAMPLE_FREQ_BASE * 1,
> +       AS73211_SAMPLE_FREQ_BASE * 2,
> +       AS73211_SAMPLE_FREQ_BASE * 4,
> +       AS73211_SAMPLE_FREQ_BASE * 8

+ Comma.

> +};

...

> +#define AS73211_OFFSET_TEMP (-66.9)
> +#define AS73211_SCALE_TEMP  0.05

In the kernel we don't do float arithmetic. How these are being used?

...

> +               *val2 = (AS73211_OFFSET_TEMP - (int)AS73211_OFFSET_TEMP) * 1000000;

> +                       *val2 = (AS73211_SCALE_TEMP - (int)AS73211_SCALE_TEMP) * 1000000;

Magic 1000000 multiplier.

I think here you got them always 0. And to fix that you need to
redefine (with also units included in the name) above constants like
#define ..._OFFSET_TEMP_mC 66500
... _SCALE_TEMP_?? 50

Consider to use definitions from
https://elixir.bootlin.com/linux/latest/source/include/linux/units.h

...

> +       }}
> +
> +       return -EINVAL;

Make it default case.

> +       }
> +
> +       return -EINVAL;

Ditto.

...

> +       }}
> +
> +       return -EINVAL;

Ditto.

...

> +       ret = devm_iio_device_register(dev, indio_dev);
> +       if (ret < 0)
> +               return ret;
> +
> +       return 0;

  return devm_iio_device_register();

And consider to drop ' < 0' for devm_*() calls. As far as I understood
your intention to explicitly leave them because of i2c_*() calls,
though devm_*() and such are different.

-- 
With Best Regards,
Andy Shevchenko