linux-kernel - Re: [PATCH v6 3/5] iio: adc: ad7949: add vref selection support

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Message-ID: <CAHp75Vd-AfmwMyYyy5ygwmvGfwZLh9VwvBEzSwW3fc99jxFpnQ@mail.gmail.com>
Date:   Mon, 16 Aug 2021 11:04:49 +0300
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Liam Beguin <liambeguin@...il.com>
Cc:     Lars-Peter Clausen <lars@...afoo.de>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Charles-Antoine Couret <charles-antoine.couret@...ensium.com>,
        Nuno Sá <Nuno.Sa@...log.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH v6 3/5] iio: adc: ad7949: add vref selection support

On Mon, Aug 16, 2021 at 12:35 AM Liam Beguin <liambeguin@...il.com> wrote:
>
> From: Liam Beguin <lvb@...hos.com>
>
> Add support for selecting the voltage reference from the devicetree.
>
> This change is required to get valid readings with all three
> vref hardware configurations supported by the ADC.
>
> For instance if the ADC isn't provided with an external reference,
> the sample request must specify an internal voltage reference to get a
> valid reading.

...

> +       /* Setup internal voltage reference */
> +       tmp = 4096000;
> +       ret = device_property_read_u32(dev, "adi,internal-ref-microvolt", &tmp);

> +       if (ret < 0 && ret != -EINVAL) {

What does this check (second part) is supposed to mean?
The first part will make it mandatory, is it the goal?

> +               dev_err(dev, "invalid value for adi,internal-ref-microvolt\n");
> +               return ret;
> +       }

-- 
With Best Regards,
Andy Shevchenko