[PATCH 0/2] iio: humditiy: hdc3020: fix units

[PATCH 0/2] iio: humditiy: hdc3020: fix units

[Dimitri Fedrau via B4 Relay]

Fix units to milli degree celsius and milli percent for temperature
respectively relative humidity measurements and thresholds.

Signed-off-by: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
---
Dimitri Fedrau (2):
      iio: humditiy: hdc3020: fix units for temperature and humidity measurement
      iio: humditiy: hdc3020: fix units for thresholds and hysteresis

 drivers/iio/humidity/hdc3020.c | 46 +++++++++++++++++++++---------------------
 1 file changed, 23 insertions(+), 23 deletions(-)
---
base-commit: 43c0f6456f801181a80b73d95def0e0fd134e1cc
change-id: 20250820-hdc3020-units-fix-91edbb8ccd07

Best regards,
-- 
Dimitri Fedrau <dimitri.fedrau@liebherr.com>

[PATCH 1/2] iio: humditiy: hdc3020: fix units for temperature and humidity measurement

[Dimitri Fedrau via B4 Relay]

From: Dimitri Fedrau <dimitri.fedrau@liebherr.com>

According to the ABI the units after application of scale and offset are
milli degrees for temperature measurements and milli percent for relative
humidity measurements. Change scale factor to fix this issue.

Fixes: c9180b8e39be ("iio: humidity: Add driver for ti HDC302x humidity sensors")
Reported-by: Chris Lesiak <chris.lesiak@licorbio.com>
Suggested-by: Chris Lesiak <chris.lesiak@licorbio.com>
Signed-off-by: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
---
 drivers/iio/humidity/hdc3020.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/iio/humidity/hdc3020.c b/drivers/iio/humidity/hdc3020.c
index ffb25596d3a8bad01d1f84a9a972561266f65d76..9de52de628e04263a2b62a512a36203d6c02c5e0 100644
--- a/drivers/iio/humidity/hdc3020.c
+++ b/drivers/iio/humidity/hdc3020.c
@@ -301,9 +301,9 @@ static int hdc3020_read_raw(struct iio_dev *indio_dev,
 	case IIO_CHAN_INFO_SCALE:
 		*val2 = 65536;
 		if (chan->type == IIO_TEMP)
-			*val = 175;
+			*val = 175000;
 		else
-			*val = 100;
+			*val = 100000;
 		return IIO_VAL_FRACTIONAL;
 
 	case IIO_CHAN_INFO_OFFSET:

-- 
2.39.5

Re: [PATCH 1/2] iio: humditiy: hdc3020: fix units for temperature and humidity measurement

[Andy Shevchenko]

On Thu, Aug 21, 2025 at 05:23:54PM +0200, Dimitri Fedrau via B4 Relay wrote:
> From: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
> 
> According to the ABI the units after application of scale and offset are
> milli degrees for temperature measurements and milli percent for relative
> humidity measurements. Change scale factor to fix this issue.

...

>  		if (chan->type == IIO_TEMP)
> -			*val = 175;
> +			*val = 175000;
>  		else
> -			*val = 100;
> +			*val = 100000;

Perhaps  use " * MILL" uin both cases?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 1/2] iio: humditiy: hdc3020: fix units for temperature and humidity measurement

[Andy Shevchenko]

On Thu, Aug 21, 2025 at 06:44:25PM +0300, Andy Shevchenko wrote:
> On Thu, Aug 21, 2025 at 05:23:54PM +0200, Dimitri Fedrau via B4 Relay wrote:

...

> >  		if (chan->type == IIO_TEMP)
> > -			*val = 175;
> > +			*val = 175000;
> >  		else
> > -			*val = 100;
> > +			*val = 100000;

> Perhaps  use " * MILL" uin both cases?

Perhaps  use " * MILLI" in both cases?

-- 
With Best Regards,
Andy Shevchenko

Re: [PATCH 1/2] iio: humditiy: hdc3020: fix units for temperature and humidity measurement

[Dimitri Fedrau]

Am Thu, Aug 21, 2025 at 06:45:02PM +0300 schrieb Andy Shevchenko:
> On Thu, Aug 21, 2025 at 06:44:25PM +0300, Andy Shevchenko wrote:
> > On Thu, Aug 21, 2025 at 05:23:54PM +0200, Dimitri Fedrau via B4 Relay wrote:
> 
> ...
> 
> > >  		if (chan->type == IIO_TEMP)
> > > -			*val = 175;
> > > +			*val = 175000;
> > >  		else
> > > -			*val = 100;
> > > +			*val = 100000;
> 
> > Perhaps  use " * MILL" uin both cases?
> 
> Perhaps  use " * MILLI" in both cases?
> 
>
Ok.

Best regards,
Dimitri Fedrau

[PATCH 2/2] iio: humditiy: hdc3020: fix units for thresholds and hysteresis

[Dimitri Fedrau via B4 Relay]

From: Dimitri Fedrau <dimitri.fedrau@liebherr.com>

According to the ABI the units after application of scale and offset are
milli degree celsius for temperature thresholds and milli percent for
relative humidity thresholds. Change scale factor to fix this issue.

Fixes: 3ad0e7e5f0cb ("iio: humidity: hdc3020: add threshold events support")
Reported-by: Chris Lesiak <chris.lesiak@licorbio.com>
Signed-off-by: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
---
 drivers/iio/humidity/hdc3020.c | 42 +++++++++++++++++++++---------------------
 1 file changed, 21 insertions(+), 21 deletions(-)

diff --git a/drivers/iio/humidity/hdc3020.c b/drivers/iio/humidity/hdc3020.c
index 9de52de628e04263a2b62a512a36203d6c02c5e0..8134d32fceedd2b88d9d4ed7bc9062759045aafe 100644
--- a/drivers/iio/humidity/hdc3020.c
+++ b/drivers/iio/humidity/hdc3020.c
@@ -379,12 +379,12 @@ static int hdc3020_thresh_get_temp(u16 thresh)
 	 * Get the temperature threshold from 9 LSBs, shift them to get
 	 * the truncated temperature threshold representation and
 	 * calculate the threshold according to the formula in the
-	 * datasheet. Result is degree celsius scaled by 65535.
+	 * datasheet. Result is degree celsius scaled by 13107.
 	 */
 	temp = FIELD_GET(HDC3020_THRESH_TEMP_MASK, thresh) <<
 	       HDC3020_THRESH_TEMP_TRUNC_SHIFT;
 
-	return -2949075 + (175 * temp);
+	return -589815 + (35 * temp);
 }
 
 static int hdc3020_thresh_get_hum(u16 thresh)
@@ -395,12 +395,12 @@ static int hdc3020_thresh_get_hum(u16 thresh)
 	 * Get the humidity threshold from 7 MSBs, shift them to get the
 	 * truncated humidity threshold representation and calculate the
 	 * threshold according to the formula in the datasheet. Result is
-	 * percent scaled by 65535.
+	 * percent scaled by 13107.
 	 */
 	hum = FIELD_GET(HDC3020_THRESH_HUM_MASK, thresh) <<
 	      HDC3020_THRESH_HUM_TRUNC_SHIFT;
 
-	return hum * 100;
+	return hum * 20;
 }
 
 static u16 hdc3020_thresh_set_temp(int s_temp, u16 curr_thresh)
@@ -455,8 +455,8 @@ int hdc3020_thresh_clr(s64 s_thresh, s64 s_hyst, enum iio_event_direction dir)
 	else
 		s_clr = s_thresh + s_hyst;
 
-	/* Divide by 65535 to get units of micro */
-	return div_s64(s_clr, 65535);
+	/* Divide by 13107 to get units of micro */
+	return div_s64(s_clr, 13107);
 }
 
 static int _hdc3020_write_thresh(struct hdc3020_data *data, u16 reg, u16 val)
@@ -507,7 +507,7 @@ static int hdc3020_write_thresh(struct iio_dev *indio_dev,
 
 	clr = ret;
 	/* Scale value to include decimal part into calculations */
-	s_val = (val < 0) ? (val * 1000000 - val2) : (val * 1000000 + val2);
+	s_val = (val < 0) ? (val * 1000 - val2) : (val * 1000 + val2);
 	switch (chan->type) {
 	case IIO_TEMP:
 		switch (info) {
@@ -523,7 +523,7 @@ static int hdc3020_write_thresh(struct iio_dev *indio_dev,
 			/* Calculate old hysteresis */
 			s_thresh = (s64)hdc3020_thresh_get_temp(thresh) * 1000000;
 			s_clr = (s64)hdc3020_thresh_get_temp(clr) * 1000000;
-			s_hyst = div_s64(abs(s_thresh - s_clr), 65535);
+			s_hyst = div_s64(abs(s_thresh - s_clr), 13107);
 			/* Set new threshold */
 			thresh = reg_val;
 			/* Set old hysteresis */
@@ -532,16 +532,16 @@ static int hdc3020_write_thresh(struct iio_dev *indio_dev,
 		case IIO_EV_INFO_HYSTERESIS:
 			/*
 			 * Function hdc3020_thresh_get_temp returns temperature
-			 * in degree celsius scaled by 65535. Scale by 1000000
+			 * in degree celsius scaled by 13107. Scale by 1000000
 			 * to be able to subtract scaled hysteresis value.
 			 */
 			s_thresh = (s64)hdc3020_thresh_get_temp(thresh) * 1000000;
 			/*
 			 * Units of s_val are in micro degree celsius, scale by
-			 * 65535 to get same units as s_thresh.
+			 * 13107 to get same units as s_thresh.
 			 */
 			s_val = min(abs(s_val), HDC3020_MAX_TEMP_HYST_MICRO);
-			s_hyst = (s64)s_val * 65535;
+			s_hyst = (s64)s_val * 13107;
 			s_clr = hdc3020_thresh_clr(s_thresh, s_hyst, dir);
 			s_clr = max(s_clr, HDC3020_MIN_TEMP_MICRO);
 			s_clr = min(s_clr, HDC3020_MAX_TEMP_MICRO);
@@ -565,7 +565,7 @@ static int hdc3020_write_thresh(struct iio_dev *indio_dev,
 			/* Calculate old hysteresis */
 			s_thresh = (s64)hdc3020_thresh_get_hum(thresh) * 1000000;
 			s_clr = (s64)hdc3020_thresh_get_hum(clr) * 1000000;
-			s_hyst = div_s64(abs(s_thresh - s_clr), 65535);
+			s_hyst = div_s64(abs(s_thresh - s_clr), 13107);
 			/* Set new threshold */
 			thresh = reg_val;
 			/* Try to set old hysteresis */
@@ -574,15 +574,15 @@ static int hdc3020_write_thresh(struct iio_dev *indio_dev,
 		case IIO_EV_INFO_HYSTERESIS:
 			/*
 			 * Function hdc3020_thresh_get_hum returns relative
-			 * humidity in percent scaled by 65535. Scale by 1000000
+			 * humidity in percent scaled by 13107. Scale by 1000000
 			 * to be able to subtract scaled hysteresis value.
 			 */
 			s_thresh = (s64)hdc3020_thresh_get_hum(thresh) * 1000000;
 			/*
-			 * Units of s_val are in micro percent, scale by 65535
+			 * Units of s_val are in micro percent, scale by 13107
 			 * to get same units as s_thresh.
 			 */
-			s_hyst = (s64)s_val * 65535;
+			s_hyst = (s64)s_val * 13107;
 			s_clr = hdc3020_thresh_clr(s_thresh, s_hyst, dir);
 			s_clr = max(s_clr, 0);
 			s_clr = min(s_clr, HDC3020_MAX_HUM_MICRO);
@@ -630,7 +630,7 @@ static int hdc3020_read_thresh(struct iio_dev *indio_dev,
 		thresh = hdc3020_thresh_get_temp(ret);
 		switch (info) {
 		case IIO_EV_INFO_VALUE:
-			*val = thresh;
+			*val = thresh * 1000;
 			break;
 		case IIO_EV_INFO_HYSTERESIS:
 			ret = hdc3020_read_be16(data, reg_clr);
@@ -638,18 +638,18 @@ static int hdc3020_read_thresh(struct iio_dev *indio_dev,
 				return ret;
 
 			clr = hdc3020_thresh_get_temp(ret);
-			*val = abs(thresh - clr);
+			*val = abs(thresh - clr) * 1000;
 			break;
 		default:
 			return -EOPNOTSUPP;
 		}
-		*val2 = 65535;
+		*val2 = 13107;
 		return IIO_VAL_FRACTIONAL;
 	case IIO_HUMIDITYRELATIVE:
 		thresh = hdc3020_thresh_get_hum(ret);
 		switch (info) {
 		case IIO_EV_INFO_VALUE:
-			*val = thresh;
+			*val = thresh * 1000;
 			break;
 		case IIO_EV_INFO_HYSTERESIS:
 			ret = hdc3020_read_be16(data, reg_clr);
@@ -657,12 +657,12 @@ static int hdc3020_read_thresh(struct iio_dev *indio_dev,
 				return ret;
 
 			clr = hdc3020_thresh_get_hum(ret);
-			*val = abs(thresh - clr);
+			*val = abs(thresh - clr) * 1000;
 			break;
 		default:
 			return -EOPNOTSUPP;
 		}
-		*val2 = 65535;
+		*val2 = 13107;
 		return IIO_VAL_FRACTIONAL;
 	default:
 		return -EOPNOTSUPP;

-- 
2.39.5

Re: [PATCH 2/2] iio: humditiy: hdc3020: fix units for thresholds and hysteresis

[Javier Carrasco]

Hello Dimitri, thank you for your patch. A few comments inline:

> From: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
>
> According to the ABI the units after application of scale and offset are
> milli degree celsius for temperature thresholds and milli percent for
> relative humidity thresholds. Change scale factor to fix this issue.

I miss some explanation of what is going on (i.e. wrong) at the moment,
the scale factor that is being used and what results are being obtained.

> @@ -379,12 +379,12 @@ static int hdc3020_thresh_get_temp(u16 thresh)
>  	 * Get the temperature threshold from 9 LSBs, shift them to get
>  	 * the truncated temperature threshold representation and
>  	 * calculate the threshold according to the formula in the

Having used 65535 back then without explaining why, or at least without using
a #define was not the best idea. It's difficult to understand why it is used
without getting into details.

13107 is even less obvious. I believe you divided 65535 by 5 everywhere in the
code, but it's not clear why.

I'd suggest a clear definition at the beginning of the code because it
is used in different parts of the code, after having explained why it
is necessary in the commit message as I mentioned before.

> -	 * datasheet. Result is degree celsius scaled by 65535.
> +	 * datasheet. Result is degree celsius scaled by 13107.
>  	 */
>  	temp = FIELD_GET(HDC3020_THRESH_TEMP_MASK, thresh) <<
>  	       HDC3020_THRESH_TEMP_TRUNC_SHIFT;
>  

Again, it's difficult to understand why everything is divided by 5.

> -	return -2949075 + (175 * temp);
> +	return -589815 + (35 * temp);
>  }
>  
>  static int hdc3020_thresh_get_hum(u16 thresh)
> @@ -395,12 +395,12 @@ static int hdc3020_thresh_get_hum(u16 thresh)
>  	 * Get the humidity threshold from 7 MSBs, shift them to get the
>  	 * truncated humidity threshold representation and calculate the
>  	 * threshold according to the formula in the datasheet. Result is
> -	 * percent scaled by 65535.
> +	 * percent scaled by 13107.
>  	 */
>  	hum = FIELD_GET(HDC3020_THRESH_HUM_MASK, thresh) <<
>  	      HDC3020_THRESH_HUM_TRUNC_SHIFT;
>  

Similarly, multiplying by 20 (100/5) looks weird for a percentage.

> -	return hum * 100;
> +	return hum * 20;
>  }

...

> @@ -630,7 +630,7 @@ static int hdc3020_read_thresh(struct iio_dev *indio_dev,
>  		thresh = hdc3020_thresh_get_temp(ret);
>  		switch (info) {
>  		case IIO_EV_INFO_VALUE:

MILLI, as suggested for [1/2]? The same would apply to the following
diffs.

> -			*val = thresh;
> +			*val = thresh * 1000;
>  			break;
>  		case IIO_EV_INFO_HYSTERESIS:
>  			ret = hdc3020_read_be16(data, reg_clr);
> @@ -638,18 +638,18 @@ static int hdc3020_read_thresh(struct iio_dev *indio_dev,
>  				return ret;
>  
>  			clr = hdc3020_thresh_get_temp(ret);

Thanks and best regards,
Javier Carrasco

Re: [PATCH 2/2] iio: humditiy: hdc3020: fix units for thresholds and hysteresis

[Dimitri Fedrau]

Hi Javier,

Am Sun, Aug 24, 2025 at 08:36:58PM +0800 schrieb Javier Carrasco:
> Hello Dimitri, thank you for your patch. A few comments inline:
> 
> > From: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
> >
> > According to the ABI the units after application of scale and offset are
> > milli degree celsius for temperature thresholds and milli percent for
> > relative humidity thresholds. Change scale factor to fix this issue.
> 
> I miss some explanation of what is going on (i.e. wrong) at the moment,
> the scale factor that is being used and what results are being obtained.
> 
Yes, will add it. Temperature is currently returned in degree celsius,
but should be returned in milli degree celsius. Relative humdity is
returned in percent, but should be returned in milli percent.

> > @@ -379,12 +379,12 @@ static int hdc3020_thresh_get_temp(u16 thresh)
> >  	 * Get the temperature threshold from 9 LSBs, shift them to get
> >  	 * the truncated temperature threshold representation and
> >  	 * calculate the threshold according to the formula in the
> 
> Having used 65535 back then without explaining why, or at least without using
> a #define was not the best idea. It's difficult to understand why it is used
> without getting into details.
>

Yes, will add a define and change the comment.

> 13107 is even less obvious. I believe you divided 65535 by 5 everywhere in the
> code, but it's not clear why.
>

The reason for it is to avoid overflows, because the thresholds and
hysteresis is now multiplied by 1000. Dividing the scale factor fixes this
issue, but makes the code even harder to understand. Will try to fix
this.

> I'd suggest a clear definition at the beginning of the code because it
> is used in different parts of the code, after having explained why it
> is necessary in the commit message as I mentioned before.
> 

Ok.

> > -	 * datasheet. Result is degree celsius scaled by 65535.
> > +	 * datasheet. Result is degree celsius scaled by 13107.
> >  	 */
> >  	temp = FIELD_GET(HDC3020_THRESH_TEMP_MASK, thresh) <<
> >  	       HDC3020_THRESH_TEMP_TRUNC_SHIFT;
> >  
> 
> Again, it's difficult to understand why everything is divided by 5.
>

Ok.

> > -	return -2949075 + (175 * temp);
> > +	return -589815 + (35 * temp);
> >  }
> >  
> >  static int hdc3020_thresh_get_hum(u16 thresh)
> > @@ -395,12 +395,12 @@ static int hdc3020_thresh_get_hum(u16 thresh)
> >  	 * Get the humidity threshold from 7 MSBs, shift them to get the
> >  	 * truncated humidity threshold representation and calculate the
> >  	 * threshold according to the formula in the datasheet. Result is
> > -	 * percent scaled by 65535.
> > +	 * percent scaled by 13107.
> >  	 */
> >  	hum = FIELD_GET(HDC3020_THRESH_HUM_MASK, thresh) <<
> >  	      HDC3020_THRESH_HUM_TRUNC_SHIFT;
> >  
> 
> Similarly, multiplying by 20 (100/5) looks weird for a percentage.
>

Ok, see above.

> > -	return hum * 100;
> > +	return hum * 20;
> >  }
> 
> ...
> 
> > @@ -630,7 +630,7 @@ static int hdc3020_read_thresh(struct iio_dev *indio_dev,
> >  		thresh = hdc3020_thresh_get_temp(ret);
> >  		switch (info) {
> >  		case IIO_EV_INFO_VALUE:
> 
> MILLI, as suggested for [1/2]? The same would apply to the following
> diffs.
> 

Ok.

> > -			*val = thresh;
> > +			*val = thresh * 1000;
> >  			break;
> >  		case IIO_EV_INFO_HYSTERESIS:
> >  			ret = hdc3020_read_be16(data, reg_clr);
> > @@ -638,18 +638,18 @@ static int hdc3020_read_thresh(struct iio_dev *indio_dev,
> >  				return ret;
> >  
> >  			clr = hdc3020_thresh_get_temp(ret);
> 
Best regards,
Dimitri Fedrau