linux-kernel - Re: [PATCH v3 14/27] staging: iio: resolver: ad2s1210: implement hysteresis as channel attr

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Date:   Fri, 29 Sep 2023 12:53:00 -0500
From:   David Lechner <dlechner@...libre.com>
To:     linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-staging@...ts.linux.dev
Cc:     David Lechner <david@...hnology.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Nuno Sá <nuno.sa@...log.com>,
        Axel Haslam <ahaslam@...libre.com>,
        Philip Molloy <pmolloy@...libre.com>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 14/27] staging: iio: resolver: ad2s1210: implement
 hysteresis as channel attr

On Fri, Sep 29, 2023 at 12:25 PM David Lechner <dlechner@...libre.com> wrote:
>
> The AD2S1210 resolver has a hysteresis feature that can be used to
> prevent flicker in the LSB of the position register. This can be either
> enabled or disabled. Disabling hysteresis is useful for increasing
> precision by oversampling.
>
> Signed-off-by: David Lechner <dlechner@...libre.com>
> ---

...

> +static int ad2s1210_read_avail(struct iio_dev *indio_dev,
> +                              struct iio_chan_spec const *chan,
> +                              const int **vals, int *type,
> +                              int *length, long mask)
> +{
> +       static const int hysteresis_available[] = { 0, 1 };

This is basically an enable/disable. Should the 1 value be changed to the
appropriate radians value since this is hysteresis on the position
(angle) channel?

> +
> +       switch (mask) {
> +       case IIO_CHAN_INFO_HYSTERESIS:
> +               switch (chan->type) {
> +               case IIO_ANGL:
> +                       *vals = hysteresis_available;
> +                       *type = IIO_VAL_INT;
> +                       *length = ARRAY_SIZE(hysteresis_available);
> +                       return IIO_AVAIL_LIST;
> +               default:
> +                       return -EINVAL;
> +               }
> +       default:
> +               return -EINVAL;
> +       }
> +}
>