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Date: Wed, 20 Oct 2021 17:52:54 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Roan van Dijk <roan@...tonic.nl>
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 Tue, 19 Oct 2021 09:30:34 +0200
Roan van Dijk <roan@...tonic.nl> wrote:
> 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.
Looks good to me. Please send as a new patch with Signed-off-by: etc
Technically it's not a 'fix' but I'll probably queue it up as one anyway
as better this definitely makes the same cycle as the driver.
Thanks,
Jonathan
>
> 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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