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Date:   Sun, 28 May 2023 18:33:13 +0100
From:   Jonathan Cameron <jic23@kernel.org>
To:     Herve Codina <herve.codina@bootlin.com>
Cc:     Liam Girdwood <lgirdwood@gmail.com>,
        Mark Brown <broonie@kernel.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Conor Dooley <conor+dt@kernel.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Jaroslav Kysela <perex@perex.cz>,
        Takashi Iwai <tiwai@suse.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@renesas.com>,
        alsa-devel@alsa-project.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-iio@vger.kernel.org,
        Christophe Leroy <christophe.leroy@csgroup.eu>,
        Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Subject: Re: [PATCH v2 5/9] iio: inkern: Add a helper to query an available
 minimum raw value
Message-ID: <20230528183313.44d7cbf5@jic23-huawei>
In-Reply-To: <20230523151223.109551-6-herve.codina@bootlin.com>
References: <20230523151223.109551-1-herve.codina@bootlin.com>
        <20230523151223.109551-6-herve.codina@bootlin.com>
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On Tue, 23 May 2023 17:12:19 +0200
Herve Codina <herve.codina@bootlin.com> wrote:

> A helper, iio_read_max_channel_raw() exists to read the available
> maximum raw value of a channel but nothing similar exists to read the
> available minimum raw value.
> 
> This new helper, iio_read_min_channel_raw(), fills the hole and can be
> used for reading the available minimum raw value of a channel.
> It is fully based on the existing iio_read_max_channel_raw().
> 
> Signed-off-by: Herve Codina <herve.codina@bootlin.com>

Acked-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

> ---
>  drivers/iio/inkern.c         | 70 ++++++++++++++++++++++++++++++++++++
>  include/linux/iio/consumer.h | 12 +++++++
>  2 files changed, 82 insertions(+)
> 
> diff --git a/drivers/iio/inkern.c b/drivers/iio/inkern.c
> index f738db9a0c04..07b26ff8a334 100644
> --- a/drivers/iio/inkern.c
> +++ b/drivers/iio/inkern.c
> @@ -915,6 +915,76 @@ int iio_read_max_channel_raw(struct iio_channel *chan, int *val)
>  }
>  EXPORT_SYMBOL_GPL(iio_read_max_channel_raw);
>  
> +static int iio_channel_read_min(struct iio_channel *chan,
> +				int *val, int *val2, int *type,
> +				enum iio_chan_info_enum info)
> +{
> +	int unused;
> +	const int *vals;
> +	int length;
> +	int ret;
> +
> +	if (!val2)
> +		val2 = &unused;
> +
> +	ret = iio_channel_read_avail(chan, &vals, type, &length, info);
> +	if (ret < 0)
> +		return ret;
> +
> +	switch (ret) {
> +	case IIO_AVAIL_RANGE:
> +		switch (*type) {
> +		case IIO_VAL_INT:
> +			*val = vals[0];
> +			break;
> +		default:
> +			*val = vals[0];
> +			*val2 = vals[1];
> +		}
> +		return 0;
> +
> +	case IIO_AVAIL_LIST:
> +		if (length <= 0)
> +			return -EINVAL;
> +		switch (*type) {
> +		case IIO_VAL_INT:
> +			*val = vals[--length];
> +			while (length) {
> +				if (vals[--length] < *val)
> +					*val = vals[length];
> +			}
> +			break;
> +		default:
> +			/* FIXME: learn about min for other iio values */
> +			return -EINVAL;
> +		}
> +		return 0;
> +
> +	default:
> +		return -EINVAL;
> +	}
> +}
> +
> +int iio_read_min_channel_raw(struct iio_channel *chan, int *val)
> +{
> +	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(chan->indio_dev);
> +	int ret;
> +	int type;
> +
> +	mutex_lock(&iio_dev_opaque->info_exist_lock);
> +	if (!chan->indio_dev->info) {
> +		ret = -ENODEV;
> +		goto err_unlock;
> +	}
> +
> +	ret = iio_channel_read_min(chan, val, NULL, &type, IIO_CHAN_INFO_RAW);
> +err_unlock:
> +	mutex_unlock(&iio_dev_opaque->info_exist_lock);
> +
> +	return ret;
> +}
> +EXPORT_SYMBOL_GPL(iio_read_min_channel_raw);
> +
>  int iio_get_channel_type(struct iio_channel *chan, enum iio_chan_type *type)
>  {
>  	struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(chan->indio_dev);
> diff --git a/include/linux/iio/consumer.h b/include/linux/iio/consumer.h
> index f536820b9cf2..e9910b41d48e 100644
> --- a/include/linux/iio/consumer.h
> +++ b/include/linux/iio/consumer.h
> @@ -301,6 +301,18 @@ int iio_write_channel_raw(struct iio_channel *chan, int val);
>   */
>  int iio_read_max_channel_raw(struct iio_channel *chan, int *val);
>  
> +/**
> + * iio_read_min_channel_raw() - read minimum available raw value from a given
> + *				channel, i.e. the minimum possible value.
> + * @chan:		The channel being queried.
> + * @val:		Value read back.
> + *
> + * Note, if standard units are required, raw reads from iio channels
> + * need the offset (default 0) and scale (default 1) to be applied
> + * as (raw + offset) * scale.
> + */
> +int iio_read_min_channel_raw(struct iio_channel *chan, int *val);
> +
>  /**
>   * iio_read_avail_channel_raw() - read available raw values from a given channel
>   * @chan:		The channel being queried.