Re: [PATCH v5 0/4] iio: chemical: Add support for Sensirion SCD4x CO2 sensor

[Roan van Dijk <roan@protonic.nl>]

On 18-10-2021 19:52, Jonathan Cameron wrote:
> On Mon, 18 Oct 2021 10:19:42 +0200
> Roan van Dijk <roan@protonic.nl> wrote:
> 
>> On 14-10-2021 19:19, Jonathan Cameron wrote:
>>> On Thu, 14 Oct 2021 10:24:54 +0200
>>> Roan van Dijk <roan@protonic.nl> wrote:
>>>    
>>>> On 13-10-2021 19:38, Jonathan Cameron wrote:
>>>>> On Sun, 10 Oct 2021 16:59:19 +0100
>>>>> Jonathan Cameron <jic23@kernel.org> wrote:
>>>>>       
>>>>>> On Fri,  8 Oct 2021 12:17:02 +0200
>>>>>> Roan van Dijk <roan@protonic.nl> wrote:
>>>>>>      
>>>>>>> This series adds support for the Sensirion SCD4x sensor.
>>>>>>>
>>>>>>> The driver supports continuous reads of temperature, relative humdity and CO2
>>>>>>> concentration. There is an interval of 5 seconds between readings. During
>>>>>>> this interval the drivers checks if the sensor has new data available.
>>>>>>>
>>>>>>> The driver is based on the scd30 driver. However, The scd4x has become too
>>>>>>> different to just expand the scd30 driver. I made a new driver instead of
>>>>>>> expanding the scd30 driver. I hope I made the right choice by doing so?
>>>>>>
>>>>>> Applied to the togreg branch of iio.git with the issues Randy mentioned tidied
>>>>>> up. Pushed out as testing for 0-day to see if it can find anything we missed
>>>>>
>>>>> And indeed - I missed a bunch of places where explicit __be16 types should have
>>>>> been used.
>>>>>
>>>>> I've applied the following fixup, shout if it's wrong.
>>>>>      
>>>> Thank you Jonathan for applying this fixup. No need to shout :) Your
>>>> changes should fix the issue.
>>>>
>>>> However, I have a question about something else. The co2 concentration
>>>> is an IIO_CHAN_INFO_RAW, but doesn't have a scale or offset at this
>>>> moment. Is an _scale always required for an _raw in the ABI? I could not
>>>> find anything in the documentation if there is a rule for this. Someone
>>>> mentioned this to me, so I want to check if I did this right.
>>>>
>>>> The sensor returns the actual co2 value upon reading, like 450 ppm. We
>>>> can set an offset of this co2 value with the calibration_forced_value
>>>> through the ABI, but this offset is handled internally by the sensor. So
>>>> there isn't anything with scaling or an offset needed at the driver side.
>>>
>>> Ah. We could have mapped this to calibbias, though here it's made more
>>> complex by other calibrations existing that don't use the value so let's
>>> leave it as it is.
>>>    
>>>>
>>>> Was I right by making it of type RAW? If needed we could make it more
>>>> like the scd30 driver, keeping it of type RAW but with scale = 1. What
>>>> should I do or is it fine as it is?
>>>
>>> Hmm. Interesting corner case in the ABI.  A _raw value without a scale
>>> normally means we don't know it for some reason.  The most common case
>>> of this is light sensors where several _raw intensity values are combined
>>> in some (typically non linear) transform to form a single measure of illuminance.
>>> Those intensity_raw channels don't have an meaningful units, but devices
>>> often have threshold events on them so we have to expose them.
>>>
>>> I would say make it a processed value, but there is a quirk.
>>> concentrations in IIO are expressed in percent not per million, so you need
>>> a scale anyway, I guess 10000?  See Documentation/ABI/testing/sysfs-bus-iio
>>>
>>>
>>> No need to do a new driver version, just send a patch tidying up this corner.
>>>    
>>
>> Hi Jonathan,
>>
>> As you suggested, these are my fixes for the concentration reading.
>>
>> The co2 reading is now a processed value and has a scale. I also added
>> the information in sysfs-bus-iio documentation, because this type of
>> processed value is new in the ABI.
>>
>> diff --git a/Documentation/ABI/testing/sysfs-bus-iio
>> b/Documentation/ABI/testing/sysfs-bus-iio
>> index c27347d3608e..66a17f4c831e 100644
>> --- a/Documentation/ABI/testing/sysfs-bus-iio
>> +++ b/Documentation/ABI/testing/sysfs-bus-iio
>> @@ -1716,6 +1716,7 @@ Description:
>>
>>    What:          /sys/bus/iio/devices/iio:deviceX/in_concentration_raw
>>    What:          /sys/bus/iio/devices/iio:deviceX/in_concentrationX_raw
>> +What:          /sys/bus/iio/devices/iio:deviceX/in_concentration_co2_input
>>    What:          /sys/bus/iio/devices/iio:deviceX/in_concentration_co2_raw
>>    What:          /sys/bus/iio/devices/iio:deviceX/in_concentrationX_co2_raw
>>    What:
>> /sys/bus/iio/devices/iio:deviceX/in_concentration_ethanol_raw
>> diff --git a/drivers/iio/chemical/scd4x.c b/drivers/iio/chemical/scd4x.c
>> index 09b34201c42b..bc1c6676029d 100644
>> --- a/drivers/iio/chemical/scd4x.c
>> +++ b/drivers/iio/chemical/scd4x.c
>> @@ -337,6 +337,7 @@ static int scd4x_read_raw(struct iio_dev *indio_dev,
>>
>>           switch (mask) {
>>           case IIO_CHAN_INFO_RAW:
>> +       case IIO_CHAN_INFO_PROCESSED:
>>                   ret = iio_device_claim_direct_mode(indio_dev);
>>                   if (ret)
>>                           return ret;
>> @@ -352,7 +353,11 @@ static int scd4x_read_raw(struct iio_dev *indio_dev,
>>                   *val = ret;
>>                   return IIO_VAL_INT;
>>           case IIO_CHAN_INFO_SCALE:
>> -               if (chan->type == IIO_TEMP) {
>> +               if (chan->type == IIO_CONCENTRATION) {
>> +                       *val = 0;
>> +                       *val2 = 100;
>> +                       return IIO_VAL_INT_PLUS_MICRO;
>> +               } else if (chan->type == IIO_TEMP) {
>>                           *val = 175000;
>>                           *val2 = 65536;
>>                           return IIO_VAL_FRACTIONAL;
>> @@ -501,7 +506,8 @@ static const struct iio_chan_spec scd4x_channels[] = {
>>                   .type = IIO_CONCENTRATION,
>>                   .channel2 = IIO_MOD_CO2,
>>                   .modified = 1,
>> -               .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
>> +               .info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED) |
>> +                                       BIT(IIO_CHAN_INFO_SCALE),
> You shouldn't have scale and processed.  If we need a scale, then it should
> be _RAW.
> 
> Jonathan

Okay, it's now a _RAW value with a scale to make the concentration value 
expressed in percent. This should be the fix then.

diff --git a/drivers/iio/chemical/scd4x.c b/drivers/iio/chemical/scd4x.c
index 09b34201c42b..b063b378c7d5 100644
--- a/drivers/iio/chemical/scd4x.c
+++ b/drivers/iio/chemical/scd4x.c
@@ -352,7 +352,11 @@ static int scd4x_read_raw(struct iio_dev *indio_dev,
                 *val = ret;
                 return IIO_VAL_INT;
         case IIO_CHAN_INFO_SCALE:
-               if (chan->type == IIO_TEMP) {
+               if (chan->type == IIO_CONCENTRATION) {
+                       *val = 0;
+                       *val2 = 100;
+                       return IIO_VAL_INT_PLUS_MICRO;
+               } else if (chan->type == IIO_TEMP) {
                         *val = 175000;
                         *val2 = 65536;
                         return IIO_VAL_FRACTIONAL;
@@ -501,7 +505,8 @@ static const struct iio_chan_spec scd4x_channels[] = {
                 .type = IIO_CONCENTRATION,
                 .channel2 = IIO_MOD_CO2,
                 .modified = 1,
-               .info_mask_separate = BIT(IIO_CHAN_INFO_RAW),
+               .info_mask_separate = BIT(IIO_CHAN_INFO_RAW) |
+                                       BIT(IIO_CHAN_INFO_SCALE),
                 .address = SCD4X_CO2,
                 .scan_index = SCD4X_CO2,
                 .scan_type = {

Thanks,

Roan

> 
>>                   .address = SCD4X_CO2,
>>                   .scan_index = SCD4X_CO2,
>>                   .scan_type = {
>>
>> Thanks,
>>
>> Roan
>>
>>> Thanks,
>>>
>>> Jonathan
>>>
>>>    
>>>> Sorry for not asking this earlier.
>>>>
>>>> Thanks,
>>>>
>>>> Roan
>>>>   
>>>>> diff --git a/drivers/iio/chemical/scd4x.c b/drivers/iio/chemical/scd4x.c
>>>>> index 09b34201c42b..ebebcb117ba2 100644
>>>>> --- a/drivers/iio/chemical/scd4x.c
>>>>> +++ b/drivers/iio/chemical/scd4x.c
>>>>> @@ -263,7 +263,7 @@ static int scd4x_write_and_fetch(struct scd4x_state *state, enum scd4x_cmd cmd,
>>>>>     static int scd4x_read_meas(struct scd4x_state *state, uint16_t *meas)
>>>>>     {
>>>>>     	int i, ret;
>>>>> -	uint16_t buf[3];
>>>>> +	__be16 buf[3];
>>>>>     
>>>>>     	ret = scd4x_read(state, CMD_READ_MEAS, buf, sizeof(buf));
>>>>>     	if (ret)
>>>>> @@ -282,12 +282,13 @@ static int scd4x_wait_meas_poll(struct scd4x_state *state)
>>>>>     	int ret;
>>>>>     
>>>>>     	do {
>>>>> +		__be16 bval;
>>>>>     		uint16_t val;
>>>>>     
>>>>> -		ret = scd4x_read(state, CMD_GET_DATA_READY, &val, sizeof(val));
>>>>> +		ret = scd4x_read(state, CMD_GET_DATA_READY, &bval, sizeof(bval));
>>>>>     		if (ret)
>>>>>     			return -EIO;
>>>>> -		val = be16_to_cpu(val);
>>>>> +		val = be16_to_cpu(bval);
>>>>>     
>>>>>     		/* new measurement available */
>>>>>     		if (val & 0x7FF)
>>>>> @@ -333,7 +334,7 @@ static int scd4x_read_raw(struct iio_dev *indio_dev,
>>>>>     {
>>>>>     	struct scd4x_state *state = iio_priv(indio_dev);
>>>>>     	int ret;
>>>>> -	uint16_t tmp;
>>>>> +	__be16 tmp;
>>>>>     
>>>>>     	switch (mask) {
>>>>>     	case IIO_CHAN_INFO_RAW:
>>>>> @@ -405,17 +406,18 @@ static ssize_t calibration_auto_enable_show(struct device *dev,
>>>>>     	struct iio_dev *indio_dev = dev_to_iio_dev(dev);
>>>>>     	struct scd4x_state *state = iio_priv(indio_dev);
>>>>>     	int ret;
>>>>> -	uint16_t val;
>>>>> +	__be16 bval;
>>>>> +	u16 val;
>>>>>     
>>>>>     	mutex_lock(&state->lock);
>>>>> -	ret = scd4x_read(state, CMD_GET_ASC, &val, sizeof(val));
>>>>> +	ret = scd4x_read(state, CMD_GET_ASC, &bval, sizeof(bval));
>>>>>     	mutex_unlock(&state->lock);
>>>>>     	if (ret) {
>>>>>     		dev_err(dev, "failed to read automatic calibration");
>>>>>     		return ret;
>>>>>     	}
>>>>>     
>>>>> -	val = (be16_to_cpu(val) & SCD4X_READY_MASK) ? 1 : 0;
>>>>> +	val = (be16_to_cpu(bval) & SCD4X_READY_MASK) ? 1 : 0;
>>>>>     
>>>>>     	return sprintf(buf, "%d\n", val);
>>>>>     }
>>>>>
>>>>>       
>>>>>>
>>>>>> Thanks,
>>>>>>
>>>>>> Jonathan
>>>>>>      
>>>>>>>
>>>>>>> Changes since v5:
>>>>>>> scd4x.c:
>>>>>>>      - Fix bug in trigger_handler
>>>>>>>
>>>>>>> Changes since v4:
>>>>>>> scd4x.c:
>>>>>>>      - Minor fixes in documentation
>>>>>>>      - Reorder trigger_handler so memcpy is not needed anymore
>>>>>>> Documentation:
>>>>>>>      - Change information about the KernelVersion for the
>>>>>>>        calibration_forced_value_available
>>>>>>>
>>>>>>> Changes since v3:
>>>>>>> scd4x.c
>>>>>>>      - Change read and write_and_fetch function parameter. CRC byte is now
>>>>>>>        hidden inside the function.
>>>>>>>      - Fix minor style issues
>>>>>>>      - Add calibration_forced_value_available attribute to the driver
>>>>>>>      - Remove including BUFFER_TRIGGERED
>>>>>>>      - Change calibbias to raw ADC readings rather than converting it to
>>>>>>>        milli degrees C.
>>>>>>> Documentation:
>>>>>>>      - Change description of driver attributes
>>>>>>>      - Add calibration_forced_value_available documentation
>>>>>>>
>>>>>>> Changes since v2:
>>>>>>> scd4x.c:
>>>>>>>      - Change boolean operations
>>>>>>>      - Document scope of lock
>>>>>>>      - Remove device *dev from struct
>>>>>>>      - Add goto block for errror handling
>>>>>>>      - Add function to read value per channel in read_raw
>>>>>>>      - Fix bug with lock in error paths
>>>>>>>      - Remove conversion of humidity and temperature values
>>>>>>>      - Add scale and offset to temperature channel
>>>>>>>      - Add scale to humidity channel
>>>>>>>      - Move memset out of locked section
>>>>>>>      - Remove unused irq functions
>>>>>>>      - Move device register at end of probe function
>>>>>>> Documentation:
>>>>>>>      - Copy content of sysfs-bus-iio-scd30 to sysfs-bus-iio
>>>>>>>      - Remove Documentation/ABI/testing/sysfs-bus-iio-scd30
>>>>>>>
>>>>>>> Changes since v1:
>>>>>>> dt-bindings:
>>>>>>>      - Separated compatible string for each sensor type
>>>>>>> scd4x.c:
>>>>>>>      - Changed probe, resume and suspend functions to static
>>>>>>>      - Added SIMPLE_DEV_PM_OPS function call for power management
>>>>>>>        operations.
>>>>>>>
>>>>>>> Roan van Dijk (4):
>>>>>>>      dt-bindings: iio: chemical: sensirion,scd4x: Add yaml description
>>>>>>>      MAINTAINERS: Add myself as maintainer of the scd4x driver
>>>>>>>      drivers: iio: chemical: Add support for Sensirion SCD4x CO2 sensor
>>>>>>>      iio: documentation: Document scd4x calibration use
>>>>>>>
>>>>>>>     Documentation/ABI/testing/sysfs-bus-iio       |  41 ++
>>>>>>>     Documentation/ABI/testing/sysfs-bus-iio-scd30 |  34 -
>>>>>>>     .../iio/chemical/sensirion,scd4x.yaml         |  46 ++
>>>>>>>     MAINTAINERS                                   |   6 +
>>>>>>>     drivers/iio/chemical/Kconfig                  |  13 +
>>>>>>>     drivers/iio/chemical/Makefile                 |   1 +
>>>>>>>     drivers/iio/chemical/scd4x.c                  | 689 ++++++++++++++++++
>>>>>>>     7 files changed, 796 insertions(+), 34 deletions(-)
>>>>>>>     delete mode 100644 Documentation/ABI/testing/sysfs-bus-iio-scd30
>>>>>>>     create mode 100644 Documentation/devicetree/bindings/iio/chemical/sensirion,scd4x.yaml
>>>>>>>     create mode 100644 drivers/iio/chemical/scd4x.c
>>>>>>>          
>>>>>>      
>>>>>       
>>>    
>