linux-kernel - Re: [PATCH v3 9/9] iio: adc: mcp3911: add support to set PGA

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Date:   Tue, 5 Jul 2022 00:02:08 +0200
From:   Andy Shevchenko <andy.shevchenko@...il.com>
To:     Marcus Folkesson <marcus.folkesson@...il.com>
Cc:     Kent Gustavsson <kent@...oris.se>,
        Jonathan Cameron <jic23@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        linux-iio <linux-iio@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3 9/9] iio: adc: mcp3911: add support to set PGA

On Mon, Jul 4, 2022 at 7:23 PM Marcus Folkesson
<marcus.folkesson@...il.com> wrote:
>
> Add support for setting the Programmable Gain Amplifiers by adjust the
> scale value.

...

> +#define MCP3911_GAIN_MASK(ch)          (0x7 << 3 * ch)

GENMASK()

...

> +       /*
> +        * For 24bit Conversion

24-bit

> +        * Raw = ((Voltage)/(Vref) * 2^23 * Gain * 1.5
> +        * Voltage = Raw * (Vref)/(2^23 * Gain * 1.5)
> +        *
> +        * ref = Reference voltage
> +        * div = (2^23 * 1.5 * gain) = 12582912 * gain
> +        */

...

> +       /* Set gain to a known value (1) */

What is '(1)'? In parentheses we usually refer to something like a
formula somewhere.

-- 
With Best Regards,
Andy Shevchenko