linux-kernel - Re: [PATCH v4] iio: adc: Add support for TI ADC108S102 and ADC128S102

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Date:   Mon, 8 May 2017 11:25:52 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Jan Kiszka <jan.kiszka@...mens.com>
Cc:     Jonathan Cameron <jic23@...nel.org>, linux-iio@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Sascha Weisenberger <sascha.weisenberger@...mens.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Mika Westerberg <mika.westerberg@...ux.intel.com>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Rob Herring <robh@...nel.org>
Subject: Re: [PATCH v4] iio: adc: Add support for TI ADC108S102 and ADC128S102

On Mon, May 8, 2017 at 10:49 AM, Jan Kiszka <jan.kiszka@...mens.com> wrote:
> This is an upstream port of an IIO driver for the TI ADC108S102 and
> ADC128S102. The former can be found on the Intel Galileo Gen2 and the
> Siemens SIMATIC IOT2000. For those boards, ACPI-based enumeration is
> included.
>
> Due to the lack of regulators under ACPI, we hard-code the voltage
> provided to the VA pin of the ADC to 5 V, the value used on Galileo and
> IOT2000. For DT usage, the regulator "vref-supply" provides this
> information. Note that DT usage has not been tested.
>
> Original author: Bogdan Pricop <bogdan.pricop@...tex.com>
> Ported from Intel Galileo Gen2 BSP to Intel Yocto kernel:
> Todor Minchev <todor@...chev.co.uk>.
>

> +static int adc108s102_read_raw(struct iio_dev *indio_dev,
> +                              struct iio_chan_spec const *chan,
> +                              int *val, int *val2, long m)
> +{
> +       struct adc108s102_state *st = iio_priv(indio_dev);
> +       int ret;
> +
> +       switch (m) {
> +       case IIO_CHAN_INFO_RAW:
> +               ret = iio_device_claim_direct_mode(indio_dev);
> +               if (ret)
> +                       return ret;
> +
> +               ret = adc108s102_scan_direct(st, chan->address);
> +
> +               iio_device_release_direct_mode(indio_dev);
> +
> +               if (ret < 0)
> +                       return ret;
> +
> +               *val = ADC108S102_RES_DATA(ret);
> +
> +               return IIO_VAL_INT;
> +       case IIO_CHAN_INFO_SCALE:
> +               if (chan->type == IIO_VOLTAGE) {
> +                       *val = st->va_millivolt;
> +                       *val2 = chan->scan_type.realbits;
> +                       return IIO_VAL_FRACTIONAL_LOG2;

> +               } else {

Redundant. and I would rather go with pattern

if (chan->type != IIO_VOLTAGE)
 return -EINVAL;

...
return IIO_VAL_FRACTIONAL_LOG2;

_Or_ use

break;

here

> +                       return -EINVAL;
> +               }
> +       default:
> +               return -EINVAL;

...and here.

> +       }

...and

return -EINVAL;

in one place.

> +}

> +       if (ACPI_COMPANION(&spi->dev)) {
> +               st->va_millivolt = ADC108S102_VA_MV_ACPI_DEFAULT;
> +       } else {

> +               st->reg = devm_regulator_get(&spi->dev, "vref");

I'm still not satisfied with this. Why we just can't use _optional()
unconditionally?
If regulator framework is broken it should be fixed first then.

> +               if (IS_ERR(st->reg))
> +                       return PTR_ERR(st->reg);
> +
> +               ret = regulator_enable(st->reg);
> +               if (ret < 0) {
> +                       dev_err(&spi->dev, "Cannot enable vref regulator\n");
> +                       return ret;
> +               }
> +
> +               ret = regulator_get_voltage(st->reg);
> +               if (ret < 0) {
> +                       dev_err(&spi->dev, "vref get voltage failed\n");
> +                       return ret;
> +               }
> +
> +               st->va_millivolt = ret / 1000;
> +       }

> +       if (!IS_ERR(st->reg))

I'm wondering why regulator framework does need this check.

> +               regulator_disable(st->reg);

-- 
With Best Regards,
Andy Shevchenko