linux-kernel - Re: [PATCH v6 04/13] iio: consumer.h: Fix raw values documentation notes

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Message-ID: <ae318459-43a2-386b-5fce-7a07fd7c6f99@csgroup.eu>
Date:   Tue, 27 Jun 2023 09:55:19 +0000
From:   Christophe Leroy <christophe.leroy@...roup.eu>
To:     Herve Codina <herve.codina@...tlin.com>,
        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>,
        Jonathan Cameron <jic23@...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>,
        Andy Shevchenko <andy.shevchenko@...il.com>
CC:     "alsa-devel@...a-project.org" <alsa-devel@...a-project.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-iio@...r.kernel.org" <linux-iio@...r.kernel.org>,
        Wojciech Ziemba <wojciech.ziemba@...el.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: Re: [PATCH v6 04/13] iio: consumer.h: Fix raw values documentation
 notes



Le 23/06/2023 à 10:58, Herve Codina a écrit :
> 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>
> Acked-by: Jonathan Cameron <Jonathan.Cameron@...wei.com>
> Reviewed-by: Andy Shevchenko <andy.shevchenko@...il.com>

Reviewed-by: Christophe Leroy <christophe.leroy@...roup.eu>

> ---
>   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);