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Message-ID: <23636d50-56b9-b7da-59b5-3568e1f3d5ca@protonic.nl>
Date: Tue, 19 Oct 2021 09:30:34 +0200
From: Roan van Dijk <roan@...tonic.nl>
To: Jonathan Cameron <jic23@...nel.org>
Cc: Rob Herring <robh+dt@...nel.org>,
Tomasz Duszynski <tomasz.duszynski@...akon.com>,
linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, david@...tonic.nl,
Lars-Peter Clausen <lars@...afoo.de>
Subject: Re: [PATCH v5 0/4] iio: chemical: Add support for Sensirion SCD4x CO2
sensor
On 18-10-2021 19:52, Jonathan Cameron wrote:
> On Mon, 18 Oct 2021 10:19:42 +0200
> Roan van Dijk <roan@...tonic.nl> wrote:
>
>> On 14-10-2021 19:19, Jonathan Cameron wrote:
>>> On Thu, 14 Oct 2021 10:24:54 +0200
>>> Roan van Dijk <roan@...tonic.nl> wrote:
>>>
>>>> On 13-10-2021 19:38, Jonathan Cameron wrote:
>>>>> On Sun, 10 Oct 2021 16:59:19 +0100
>>>>> Jonathan Cameron <jic23@...nel.org> wrote:
>>>>>
>>>>>> On Fri, 8 Oct 2021 12:17:02 +0200
>>>>>> Roan van Dijk <roan@...tonic.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
>>>>>>>
>>>>>>
>>>>>
>>>
>
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