linux-kernel - Re: [PATCH v2 4/9] iio: consumer.h: Fix raw values documentation notes

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Date:   Sun, 28 May 2023 18:29:47 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Herve Codina <herve.codina@...tlin.com>
Cc:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Kuninori Morimoto <kuninori.morimoto.gx@...esas.com>,
        alsa-devel@...a-project.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
        Christophe Leroy <christophe.leroy@...roup.eu>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>
Subject: Re: [PATCH v2 4/9] iio: consumer.h: Fix raw values documentation
 notes

On Tue, 23 May 2023 17:12:18 +0200
Herve Codina <herve.codina@...tlin.com> wrote:

> The raw values notes mention 'ADC counts' and are not fully accurate.
> 
> Reword the notes in order to remove the 'ADC counts' and describe the
> conversion needed between a raw value and a value in the standard units.
> 
> Signed-off-by: Herve Codina <herve.codina@...tlin.com>
I'm not 100% sure what path this will take - though hopefully and immutable
branch I can pick up will be involved. On that basis I won't pick this up
now and instead give

Acked-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> ---
>  include/linux/iio/consumer.h | 25 +++++++++++++++----------
>  1 file changed, 15 insertions(+), 10 deletions(-)
> 
> diff --git a/include/linux/iio/consumer.h b/include/linux/iio/consumer.h
> index 6802596b017c..f536820b9cf2 100644
> --- a/include/linux/iio/consumer.h
> +++ b/include/linux/iio/consumer.h
> @@ -201,8 +201,9 @@ struct iio_dev
>   * @chan:		The channel being queried.
>   * @val:		Value read back.
>   *
> - * Note raw reads from iio channels are in adc counts and hence
> - * scale will need to be applied if standard units required.
> + * 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_channel_raw(struct iio_channel *chan,
>  			 int *val);
> @@ -212,8 +213,9 @@ int iio_read_channel_raw(struct iio_channel *chan,
>   * @chan:		The channel being queried.
>   * @val:		Value read back.
>   *
> - * Note raw reads from iio channels are in adc counts and hence
> - * scale will need to be applied if standard units required.
> + * 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.
>   *
>   * In opposit to the normal iio_read_channel_raw this function
>   * returns the average of multiple reads.
> @@ -281,8 +283,9 @@ int iio_read_channel_attribute(struct iio_channel *chan, int *val,
>   * @chan:		The channel being queried.
>   * @val:		Value being written.
>   *
> - * Note raw writes to iio channels are in dac counts and hence
> - * scale will need to be applied if standard units required.
> + * Note that for raw writes to iio channels, if the value provided is
> + * in standard units, the affect of the scale and offset must be removed
> + * as (value / scale) - offset.
>   */
>  int iio_write_channel_raw(struct iio_channel *chan, int val);
>  
> @@ -292,8 +295,9 @@ int iio_write_channel_raw(struct iio_channel *chan, int val);
>   * @chan:		The channel being queried.
>   * @val:		Value read back.
>   *
> - * Note raw reads from iio channels are in adc counts and hence
> - * scale will need to be applied if standard units are required.
> + * 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_max_channel_raw(struct iio_channel *chan, int *val);
>  
> @@ -308,8 +312,9 @@ int iio_read_max_channel_raw(struct iio_channel *chan, int *val);
>   * For ranges, three vals are always returned; min, step and max.
>   * For lists, all the possible values are enumerated.
>   *
> - * Note raw available values from iio channels are in adc counts and
> - * hence scale will need to be applied if standard units are required.
> + * Note, if standard units are required, raw available values from iio
> + * channels need the offset (default 0) and scale (default 1) to be applied
> + * as (raw + offset) * scale.
>   */
>  int iio_read_avail_channel_raw(struct iio_channel *chan,
>  			       const int **vals, int *length);