linux-kernel - [PATCH v4 04/13] iio: consumer.h: Fix raw values documentation notes

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Message-Id: <20230614074904.29085-5-herve.codina@bootlin.com>
Date:   Wed, 14 Jun 2023 09:48:55 +0200
From:   Herve Codina <herve.codina@...tlin.com>
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, 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>,
        Jonathan Cameron <Jonathan.Cameron@...wei.com>
Subject: [PATCH v4 04/13] iio: consumer.h: Fix raw values documentation notes

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>
---
 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);
-- 
2.40.1