Re: [RFC PATCH v4 1/1] iio/scmi: Adding support for IIO SCMI Based Sensors

From: Jyoti Bhayana
Date: Tue Feb 02 2021 - 01:54:38 EST

Hi Jonathan,

I wanted to clarify a few things before I upload the next version of
the patch. Can you please help provide some more details regarding the
following questions?

1) You mentioned that
> perhaps we just need to do the maths in here rather than rely
on core handling of IIO_VAL_FRACTIONAL.
> That would give us a greater potential range"

Can you please clarify with some examples of how I can use
IIO_VAL_INT_PLUS_MICRO to represent a range which is larger than 32
bits without changing the sensor scale?

2) > #define ilog10(x) (ilog2(x) / const_ilog2(10))
> That feels like it's probably not great for precision"
I am only using this calculation to get the power of 10 multiplier
used when setting the scmi sensor update interval, so the exact
precision after the decimal point is not necessary. I am only using
at one place in the code, so either I can remove the #define and
directly use it in the function or change the name of the #define.
Please let me know what you think

3)
> +#define UHZ_PER_HZ 1000000UL
> +#define ODR_EXPAND(odr, uodr) (((odr) * 1000000ULL) + (uodr))

>Prefix these if driver specific.
>For those that aren't perhaps we can think about putting them in
>generic headers

UHZ_PER_HZ is generic and not driver specific. Either I can use
USEC_PER_SEC which is already defined in include/linux/time64.h or we
can put UHZ_PER_HZ in a generic header instead. Please let me know
your preference and also which header file you think it needs to be
added in case of generic header.
ODR_EXPAND is only used in one place in the code, and I can remove the
#define and use it directly in the function. Let me know if that will
be fine with you,

Thanks,
Jyoti






On Sun, Jan 31, 2021 at 5:11 AM Jonathan Cameron <jic23@xxxxxxxxxx> wrote:
>
> On Fri, 29 Jan 2021 22:18:18 +0000
> Jyoti Bhayana <jbhayana@xxxxxxxxxx> wrote:
>
> > This change provides ARM SCMI Protocol based IIO device.
> > This driver provides support for Accelerometer and Gyroscope using
> > SCMI Sensor Protocol extensions added in the SCMIv3.0 ARM specification
> >
> > Signed-off-by: Jyoti Bhayana <jbhayana@xxxxxxxxxx>
>
> A few minor things noticed on a fresh read through, but mostly I think
> we are down to figuring out how to deal with the range (as discussed
> in the thread continuing on v3).
>
> On another note, probably time to drop the RFC or give a bit more detail
> on why you think this isn't ready to be applied.
>
> Thanks,
>
> Jonathan
>
> > ---
> > MAINTAINERS | 6 +
> > drivers/iio/common/Kconfig | 1 +
> > drivers/iio/common/Makefile | 1 +
> > drivers/iio/common/scmi_sensors/Kconfig | 18 +
> > drivers/iio/common/scmi_sensors/Makefile | 5 +
> > drivers/iio/common/scmi_sensors/scmi_iio.c | 742 +++++++++++++++++++++
> > 6 files changed, 773 insertions(+)
> > create mode 100644 drivers/iio/common/scmi_sensors/Kconfig
> > create mode 100644 drivers/iio/common/scmi_sensors/Makefile
> > create mode 100644 drivers/iio/common/scmi_sensors/scmi_iio.c
> >
> > diff --git a/MAINTAINERS b/MAINTAINERS
> > index b516bb34a8d5..ccf37d43ab41 100644
> > --- a/MAINTAINERS
> > +++ b/MAINTAINERS
> > @@ -8567,6 +8567,12 @@ S: Maintained
> > F: Documentation/devicetree/bindings/iio/multiplexer/io-channel-mux.txt
> > F: drivers/iio/multiplexer/iio-mux.c
> >
> > +IIO SCMI BASED DRIVER
> > +M: Jyoti Bhayana <jbhayana@xxxxxxxxxx>
> > +L: linux-iio@xxxxxxxxxxxxxxx
> > +S: Maintained
> > +F: drivers/iio/common/scmi_sensors/scmi_iio.c
> > +
> > IIO SUBSYSTEM AND DRIVERS
> > M: Jonathan Cameron <jic23@xxxxxxxxxx>
> > R: Lars-Peter Clausen <lars@xxxxxxxxxx>
> > diff --git a/drivers/iio/common/Kconfig b/drivers/iio/common/Kconfig
> > index 2b9ee9161abd..0334b4954773 100644
> > --- a/drivers/iio/common/Kconfig
> > +++ b/drivers/iio/common/Kconfig
> > @@ -6,5 +6,6 @@
> > source "drivers/iio/common/cros_ec_sensors/Kconfig"
> > source "drivers/iio/common/hid-sensors/Kconfig"
> > source "drivers/iio/common/ms_sensors/Kconfig"
> > +source "drivers/iio/common/scmi_sensors/Kconfig"
> > source "drivers/iio/common/ssp_sensors/Kconfig"
> > source "drivers/iio/common/st_sensors/Kconfig"
> > diff --git a/drivers/iio/common/Makefile b/drivers/iio/common/Makefile
> > index 4bc30bb548e2..fad40e1e1718 100644
> > --- a/drivers/iio/common/Makefile
> > +++ b/drivers/iio/common/Makefile
> > @@ -11,5 +11,6 @@
> > obj-y += cros_ec_sensors/
> > obj-y += hid-sensors/
> > obj-y += ms_sensors/
> > +obj-y += scmi_sensors/
> > obj-y += ssp_sensors/
> > obj-y += st_sensors/
> > diff --git a/drivers/iio/common/scmi_sensors/Kconfig b/drivers/iio/common/scmi_sensors/Kconfig
> > new file mode 100644
> > index 000000000000..67e084cbb1ab
> > --- /dev/null
> > +++ b/drivers/iio/common/scmi_sensors/Kconfig
> > @@ -0,0 +1,18 @@
> > +#
> > +# IIO over SCMI
> > +#
> > +# When adding new entries keep the list in alphabetical order
> > +
> > +menu "IIO SCMI Sensors"
> > +
> > +config IIO_SCMI
> > + tristate "IIO SCMI"
> > + depends on ARM_SCMI_PROTOCOL
> > + select IIO_BUFFER
> > + select IIO_KFIFO_BUF
> > + help
> > + Say yes here to build support for IIO SCMI Driver.
> > + This provides ARM SCMI Protocol based IIO device.
> > + This driver provides support for accelerometer and gyroscope
> > + sensors available on SCMI based platforms.
> > +endmenu
> > diff --git a/drivers/iio/common/scmi_sensors/Makefile b/drivers/iio/common/scmi_sensors/Makefile
> > new file mode 100644
> > index 000000000000..f13140a2575a
> > --- /dev/null
> > +++ b/drivers/iio/common/scmi_sensors/Makefile
> > @@ -0,0 +1,5 @@
> > +# SPDX - License - Identifier : GPL - 2.0 - only
> > +#
> > +# Makefile for the IIO over SCMI
> > +#
> > +obj-$(CONFIG_IIO_SCMI) += scmi_iio.o
> > diff --git a/drivers/iio/common/scmi_sensors/scmi_iio.c b/drivers/iio/common/scmi_sensors/scmi_iio.c
> > new file mode 100644
> > index 000000000000..331ffaffd06f
> > --- /dev/null
> > +++ b/drivers/iio/common/scmi_sensors/scmi_iio.c
> > @@ -0,0 +1,742 @@
> > +// SPDX-License-Identifier: GPL-2.0
> > +
> > +/*
> > + * System Control and Management Interface(SCMI) based IIO sensor driver
> > + *
> > + * Copyright (C) 2020 Google LLC
> Probably want to include 2021 given you are still making substantial changes ;)
>
> > + */
> > +
> > +#include <linux/delay.h>
> > +#include <linux/err.h>
> > +#include <linux/iio/buffer.h>
> > +#include <linux/iio/iio.h>
> > +#include <linux/iio/kfifo_buf.h>
> > +#include <linux/iio/sysfs.h>
> > +#include <linux/kernel.h>
> > +#include <linux/kthread.h>
> > +#include <linux/module.h>
> > +#include <linux/scmi_protocol.h>
> > +#include <linux/time.h>
> > +#include <linux/types.h>
> > +
> > +#define ilog10(x) (ilog2(x) / const_ilog2(10))
>
> That feels like it's probably not great for precision.
>
> > +#define UHZ_PER_HZ 1000000UL
> > +#define ODR_EXPAND(odr, uodr) (((odr) * 1000000ULL) + (uodr))
>
> Prefix these if driver specific.
> For those that aren't perhaps we can think about putting them in
> generic headers.
>
>
> > +#define MAX_NUM_OF_CHANNELS 4
> > +#define H32(x) (FIELD_GET(GENMASK_ULL(63, 32), (x)))
> > +#define L32(x) (FIELD_GET(GENMASK_ULL(31, 0), (x)))
>
> Can we use upper_32_bits() etc in stead of these?
>
> > +
> > +struct scmi_iio_priv {
> > + struct scmi_handle *handle;
> > + const struct scmi_sensor_info *sensor_info;
> > + struct iio_dev *indio_dev;
> > + long long iio_buf[MAX_NUM_OF_CHANNELS];
> > + struct notifier_block sensor_update_nb;
> > + u32 *freq_avail;
> > + /*
> > + * range_avail = [minRange resolution maxRange]
> > + * with IIO val type as IIO_VAL_FRACTIONAL.
> > + * Hence, array of size 6.
> > + */
> > + int range_avail[6];
> > +};
> > +
> > +static int scmi_iio_sensor_update_cb(struct notifier_block *nb,
> > + unsigned long event, void *data)
> > +{
> > + struct scmi_sensor_update_report *sensor_update = data;
> > + struct iio_dev *scmi_iio_dev;
> > + struct scmi_iio_priv *sensor;
> > + s8 tstamp_scale;
> > + u64 time, time_ns;
> > + int i;
> > +
> > + if (sensor_update->readings_count == 0)
> > + return NOTIFY_DONE;
> > +
> > + sensor = container_of(nb, struct scmi_iio_priv, sensor_update_nb);
> > +
> > + for (i = 0; i < sensor_update->readings_count; i++)
> > + sensor->iio_buf[i] = sensor_update->readings[i].value;
> > +
> > + if (!sensor->sensor_info->timestamped) {
> > + time_ns = sensor_update->timestamp;
> > + } else {
> > + /*
> > + * All the axes are supposed to have the same value for timestamp.
> > + * We are just using the values from the Axis 0 here.
>
> Slightly odd indenting of comment here.
>
> > + */
> > + time = sensor_update->readings[0].timestamp;
> > +
> > + /*
> > + * Timestamp returned by SCMI is in seconds and is equal to
> > + * time * power-of-10 multiplier(tstamp_scale) seconds.
> > + * Converting the timestamp to nanoseconds below.
> > + */
> > + tstamp_scale = sensor->sensor_info->tstamp_scale +
> > + ilog10(NSEC_PER_SEC);
> > + if (tstamp_scale < 0)
> > + time_ns = div64_u64(time,
> > + int_pow(10, abs(tstamp_scale)));
> > + else
> > + time_ns = time * int_pow(10, tstamp_scale);
> > + }
> > +
> > + scmi_iio_dev = sensor->indio_dev;
> > + iio_push_to_buffers_with_timestamp(scmi_iio_dev, sensor->iio_buf,
> > + time_ns);
> > + return NOTIFY_OK;
> > +}
> > +
> > +static int scmi_iio_buffer_preenable(struct iio_dev *iio_dev)
> > +{
> > + struct scmi_iio_priv *sensor = iio_priv(iio_dev);
> > + u32 sensor_id = sensor->sensor_info->id;
> > + u32 sensor_config;
> > + int err;
> > +
> > + if (sensor->sensor_info->timestamped)
> > + sensor_config |= FIELD_PREP(SCMI_SENS_CFG_TSTAMP_ENABLED_MASK,
> > + SCMI_SENS_CFG_TSTAMP_ENABLE);
> > +
> > + sensor_config |= FIELD_PREP(SCMI_SENS_CFG_SENSOR_ENABLED_MASK,
> > + SCMI_SENS_CFG_SENSOR_ENABLE);
> > +
> > + err = sensor->handle->notify_ops->register_event_notifier(sensor->handle,
> > + SCMI_PROTOCOL_SENSOR, SCMI_EVENT_SENSOR_UPDATE,
> > + &sensor_id, &sensor->sensor_update_nb);
> > + if (err) {
> > + dev_err(&iio_dev->dev,
> > + "Error in registering sensor update notifier for sensor %s err %d",
> > + sensor->sensor_info->name, err);
> > + return err;
> > + }
> > +
> > + err = sensor->handle->sensor_ops->config_set(sensor->handle,
> > + sensor->sensor_info->id, sensor_config);
> > + if (err) {
> > + sensor->handle->notify_ops->unregister_event_notifier(sensor->handle,
> > + SCMI_PROTOCOL_SENSOR, SCMI_EVENT_SENSOR_UPDATE,
> > + &sensor_id, &sensor->sensor_update_nb);
> > + dev_err(&iio_dev->dev, "Error in enabling sensor %s err %d",
> > + sensor->sensor_info->name, err);
> > + }
> > +
> > + return err;
> > +}
> > +
> > +static int scmi_iio_buffer_postdisable(struct iio_dev *iio_dev)
> > +{
> > + struct scmi_iio_priv *sensor = iio_priv(iio_dev);
> > + u32 sensor_id = sensor->sensor_info->id;
> > + u32 sensor_config = 0;
> > + int err;
> > +
> > + sensor_config |= FIELD_PREP(SCMI_SENS_CFG_SENSOR_ENABLED_MASK,
> > + SCMI_SENS_CFG_SENSOR_DISABLE);
> > +
> > + err = sensor->handle->notify_ops->unregister_event_notifier(sensor->handle,
> > + SCMI_PROTOCOL_SENSOR, SCMI_EVENT_SENSOR_UPDATE,
> > + &sensor_id, &sensor->sensor_update_nb);
> > + if (err) {
> > + dev_err(&iio_dev->dev,
> > + "Error in unregistering sensor update notifier for sensor %s err %d",
> > + sensor->sensor_info->name, err);
> > + return err;
> > + }
> > +
> > + err = sensor->handle->sensor_ops->config_set(sensor->handle, sensor_id,
> > + sensor_config);
> > + if (err) {
> > + dev_err(&iio_dev->dev,
> > + "Error in disabling sensor %s with err %d",
> > + sensor->sensor_info->name, err);
> > + }
> > +
> > + return err;
> > +}
> > +
> > +static const struct iio_buffer_setup_ops scmi_iio_buffer_ops = {
> > + .preenable = scmi_iio_buffer_preenable,
> > + .postdisable = scmi_iio_buffer_postdisable,
> > +};
> > +
> > +static int scmi_iio_read_avail(struct iio_dev *iio_dev,
> > + struct iio_chan_spec const *chan,
> > + const int **vals, int *type, int *length,
> > + long mask)
> > +{
> > + struct scmi_iio_priv *sensor = iio_priv(iio_dev);
> > +
> > + switch (mask) {
> > + case IIO_CHAN_INFO_SAMP_FREQ:
> > + *vals = sensor->freq_avail;
> > + *type = IIO_VAL_INT_PLUS_MICRO;
> > + *length = sensor->sensor_info->intervals.count * 2;
> > + if (sensor->sensor_info->intervals.segmented)
> > + return IIO_AVAIL_RANGE;
> > + else
> > + return IIO_AVAIL_LIST;
> > + case IIO_CHAN_INFO_RAW:
> > + *vals = sensor->range_avail;
> > + *type = IIO_VAL_FRACTIONAL;
> > + *length = ARRAY_SIZE(sensor->range_avail);
> > + return IIO_AVAIL_RANGE;
> > + default:
> > + return -EINVAL;
> > + }
> > +}
> > +
> > +static int scmi_iio_set_odr_val(struct iio_dev *iio_dev, int val, int val2)
> > +{
> > + struct scmi_iio_priv *sensor = iio_priv(iio_dev);
> > + u64 sec, mult, uHz;
> > + u32 sensor_config;
> > +
> > + int err = sensor->handle->sensor_ops->config_get(sensor->handle,
> > + sensor->sensor_info->id, &sensor_config);
> > + if (err) {
> > + dev_err(&iio_dev->dev,
> > + "Error in getting sensor config for sensor %s err %d",
> > + sensor->sensor_info->name, err);
> > + return err;
> > + }
> > +
> > + uHz = ODR_EXPAND(val, val2);
> > +
> > + /*
> > + * The seconds field in the sensor interval in SCMI is 16 bits long
> > + * Therefore seconds = 1/Hz <= 0xFFFF. As floating point calculations are
> > + * discouraged in the kernel driver code, to calculate the scale factor (sf)
> > + * (1* 1000000 * sf)/uHz <= 0xFFFF. Therefore, sf <= (uHz * 0xFFFF)/1000000
> > + */
> > + mult = ilog10(((u64)uHz * 0xFFFF) / UHZ_PER_HZ);
> > +
> > + sec = div64_u64(int_pow(10, mult) * UHZ_PER_HZ, uHz);
> > + if (sec == 0) {
> > + dev_err(&iio_dev->dev,
> > + "Trying to set invalid sensor update value for sensor %s",
> > + sensor->sensor_info->name);
> > + return -EINVAL;
> > + }
> > +
> > + sensor_config &= ~SCMI_SENS_CFG_UPDATE_SECS_MASK;
> > + sensor_config |= FIELD_PREP(SCMI_SENS_CFG_UPDATE_SECS_MASK, sec);
> > + sensor_config &= ~SCMI_SENS_CFG_UPDATE_EXP_MASK;
> > + sensor_config |= FIELD_PREP(SCMI_SENS_CFG_UPDATE_EXP_MASK, -mult);
> > +
> > + if (sensor->sensor_info->timestamped) {
> > + sensor_config &= ~SCMI_SENS_CFG_TSTAMP_ENABLED_MASK;
> > + sensor_config |= FIELD_PREP(SCMI_SENS_CFG_TSTAMP_ENABLED_MASK,
> > + SCMI_SENS_CFG_TSTAMP_ENABLE);
> > + }
> > +
> > + sensor_config &= ~SCMI_SENS_CFG_ROUND_MASK;
> > + sensor_config |=
> > + FIELD_PREP(SCMI_SENS_CFG_ROUND_MASK, SCMI_SENS_CFG_ROUND_AUTO);
> > +
> > + err = sensor->handle->sensor_ops->config_set(sensor->handle,
> > + sensor->sensor_info->id, sensor_config);
> > + if (err)
> > + dev_err(&iio_dev->dev,
> > + "Error in setting sensor update interval for sensor %s value %u err %d",
> > + sensor->sensor_info->name, sensor_config, err);
> > +
> > + return err;
> > +}
> > +
> > +static int scmi_iio_write_raw(struct iio_dev *iio_dev,
> > + struct iio_chan_spec const *chan, int val,
> > + int val2, long mask)
> > +{
> > + int err;
> > +
> > + switch (mask) {
> > + case IIO_CHAN_INFO_SAMP_FREQ:
> > + mutex_lock(&iio_dev->mlock);
> > + err = scmi_iio_set_odr_val(iio_dev, val, val2);
> > + mutex_unlock(&iio_dev->mlock);
> > + return err;
> > + default:
> > + return -EINVAL;
> > + }
> > +}
> > +
> > +static u64 scmi_iio_convert_interval_to_ns(u32 val)
> > +{
> > + u64 sensor_update_interval =
> > + SCMI_SENS_INTVL_GET_SECS(val) * NSEC_PER_SEC;
> > + u64 sensor_interval_mult;
> > + int mult;
> > +
> > + mult = SCMI_SENS_INTVL_GET_EXP(val);
> > + if (mult < 0) {
> > + sensor_interval_mult = int_pow(10, abs(mult));
> > + sensor_update_interval =
> > + sensor_update_interval / sensor_interval_mult;
> > + } else {
> > + sensor_interval_mult = int_pow(10, mult);
> > + sensor_update_interval =
> > + sensor_update_interval * sensor_interval_mult;
> > + }
> > + return sensor_update_interval;
> > +}
> > +
> > +static void convert_ns_to_freq(u64 interval_ns, u64 *hz, u64 *uhz)
> > +{
> > + u64 rem;
> > +
> > + *hz = div64_u64_rem(NSEC_PER_SEC, interval_ns, &rem);
> > + *uhz = (rem * 1000000UL) / interval_ns;
> > +}
> > +
> > +static int scmi_iio_get_odr_val(struct iio_dev *iio_dev, int *val, int *val2)
> > +{
> > + u64 sensor_update_interval, sensor_interval_mult, hz, uhz;
> > + struct scmi_iio_priv *sensor = iio_priv(iio_dev);
> > + u32 sensor_config;
> > + int mult;
> > +
> > + int err = sensor->handle->sensor_ops->config_get(sensor->handle,
> > + sensor->sensor_info->id, &sensor_config);
> > + if (err) {
> > + dev_err(&iio_dev->dev,
> > + "Error in getting sensor config for sensor %s err %d",
> > + sensor->sensor_info->name, err);
> > + return err;
> > + }
> > +
> > + sensor_update_interval =
> > + SCMI_SENS_CFG_GET_UPDATE_SECS(sensor_config) * NSEC_PER_SEC;
> > +
> > + mult = SCMI_SENS_CFG_GET_UPDATE_EXP(sensor_config);
> > + if (mult < 0) {
> > + sensor_interval_mult = int_pow(10, abs(mult));
> > + sensor_update_interval =
> > + sensor_update_interval / sensor_interval_mult;
> > + } else {
> > + sensor_interval_mult = int_pow(10, mult);
> > + sensor_update_interval =
> > + sensor_update_interval * sensor_interval_mult;
> > + }
> > +
> > + convert_ns_to_freq(sensor_update_interval, &hz, &uhz);
> > + *val = hz;
> > + *val2 = uhz;
> > + return 0;
> > +}
> > +
> > +static int scmi_iio_read_raw(struct iio_dev *iio_dev,
> > + struct iio_chan_spec const *ch, int *val,
> > + int *val2, long mask)
> > +{
> > + struct scmi_iio_priv *sensor = iio_priv(iio_dev);
> > + s8 scale;
> > + int ret;
> > +
> > + switch (mask) {
> > + case IIO_CHAN_INFO_SCALE:
> > + scale = sensor->sensor_info->axis[ch->scan_index].scale;
> > + if (scale < 0) {
> > + *val = 1;
> > + *val2 = int_pow(10, abs(scale));
> > + return IIO_VAL_FRACTIONAL;
> > + }
> > + *val = int_pow(10, scale);
> > + return IIO_VAL_INT;
> > + case IIO_CHAN_INFO_SAMP_FREQ:
> > + ret = scmi_iio_get_odr_val(iio_dev, val, val2);
> > + return ret ? ret : IIO_VAL_INT_PLUS_MICRO;
> > + default:
> > + return -EINVAL;
> > + }
> > +}
> > +
> > +static const struct iio_info scmi_iio_info = {
> > + .read_raw = scmi_iio_read_raw,
> > + .read_avail = scmi_iio_read_avail,
> > + .write_raw = scmi_iio_write_raw,
> > +};
> > +
> > +static void scmi_iio_set_timestamp_channel(struct iio_chan_spec *iio_chan,
> > + int scan_index)
> > +{
> > + iio_chan->type = IIO_TIMESTAMP;
> > + iio_chan->channel = -1;
> > + iio_chan->scan_index = scan_index;
> > + iio_chan->scan_type.sign = 'u';
> > + iio_chan->scan_type.realbits = 64;
> > + iio_chan->scan_type.storagebits = 64;
> > +}
> > +
> > +static void scmi_iio_set_data_channel(struct iio_chan_spec *iio_chan,
> > + enum iio_chan_type type,
> > + enum iio_modifier mod, int scan_index)
> > +{
> > + iio_chan->type = type;
> > + iio_chan->modified = 1;
> > + iio_chan->channel2 = mod;
> > + iio_chan->info_mask_separate = BIT(IIO_CHAN_INFO_SCALE);
> > + iio_chan->info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ);
> > + iio_chan->info_mask_shared_by_type_available =
> > + BIT(IIO_CHAN_INFO_SAMP_FREQ) | BIT(IIO_CHAN_INFO_RAW);
> > + iio_chan->scan_index = scan_index;
> > + iio_chan->scan_type.sign = 's';
> > + iio_chan->scan_type.realbits = 64;
> > + iio_chan->scan_type.storagebits = 64;
> > + iio_chan->scan_type.endianness = IIO_LE;
> > +}
> > +
> > +static int scmi_iio_get_chan_modifier(const char *name,
> > + enum iio_modifier *modifier)
> > +{
> > + char *pch, mod;
> > +
> > + if (!name)
> > + return -EINVAL;
> > +
> > + pch = strrchr(name, '_');
> > + if (!pch)
> > + return -EINVAL;
> > +
> > + mod = *(pch + 1);
> > + switch (mod) {
> > + case 'X':
> > + *modifier = IIO_MOD_X;
> > + return 0;
> > + case 'Y':
> > + *modifier = IIO_MOD_Y;
> > + return 0;
> > + case 'Z':
> > + *modifier = IIO_MOD_Z;
> > + return 0;
> > + default:
> > + return -EINVAL;
> > + }
> > +}
> > +
> > +static int scmi_iio_get_chan_type(u8 scmi_type, enum iio_chan_type *iio_type)
> > +{
> > + switch (scmi_type) {
> > + case METERS_SEC_SQUARED:
> > + *iio_type = IIO_ACCEL;
> > + return 0;
> > + case RADIANS_SEC:
> > + *iio_type = IIO_ANGL_VEL;
> > + return 0;
> > + default:
> > + return -EINVAL;
> > + }
> > +}
> > +
> > +static int scmi_iio_get_sensor_max_range(struct iio_dev *iio_dev, int *val,
> > + int *val2)
> > +{
> > + struct scmi_iio_priv *sensor = iio_priv(iio_dev);
> > + int max_range_high, max_range_low;
> > + long long max_range;
> > +
> > + /*
> > + * All the axes are supposed to have the same value for max range.
> > + * We are just using the values from the Axis 0 here.
> > + */
> > + if (sensor->sensor_info->axis[0].extended_attrs) {
> > + max_range = sensor->sensor_info->axis[0].attrs.max_range;
> > + max_range_high = H32(max_range);
> > + max_range_low = L32(max_range);
> > +
> > + /*
> > + * As IIO Val types have no provision for 64 bit values,
> > + * this driver only supports sensors whose maximum range
> > + * reported by the SCMI Platform fits within lower 32 bits
> > + */
> > + if (max_range_high != 0)
> > + return -EINVAL;
> > +
> > + *val = max_range_low;
> > + *val2 = 1;
> > + }
> > + return 0;
> > +}
> > +
> > +static void scmi_iio_get_sensor_resolution(struct iio_dev *iio_dev, int *val,
> > + int *val2)
> > +{
> > + struct scmi_iio_priv *sensor = iio_priv(iio_dev);
> > +
> > + /*
> > + * All the axes are supposed to have the same value for resolution
> > + * and exponent. We are just using the values from the Axis 0 here.
> > + */
> > + if (sensor->sensor_info->axis[0].extended_attrs) {
> > + uint resolution = sensor->sensor_info->axis[0].resolution;
> > + s8 exponent = sensor->sensor_info->axis[0].exponent;
> > + s8 scale = sensor->sensor_info->axis[0].scale;
> > +
> > + /*
> > + * To provide the raw value for the resolution to the userspace,
> > + * need to divide the resolution exponent by the sensor scale
> > + */
> > + exponent = exponent - scale;
> > + if (exponent >= 0) {
> > + *val = resolution * int_pow(10, exponent);
> > + *val2 = 1;
> > + } else {
> > + *val = resolution;
> > + *val2 = int_pow(10, abs(exponent));
> > + }
> > + }
> > +}
> > +
> > +static int scmi_iio_get_sensor_min_range(struct iio_dev *iio_dev, int *val,
> > + int *val2)
> > +{
> > + struct scmi_iio_priv *sensor = iio_priv(iio_dev);
> > + int min_range_high, min_range_low;
> > + long long min_range;
> > +
> > + /*
> > + * All the axes are supposed to have the same value for min range.
> > + * We are just using the values from the Axis 0 here.
> > + */
> > + if (sensor->sensor_info->axis[0].extended_attrs) {
> > + min_range = sensor->sensor_info->axis[0].attrs.min_range;
> > + min_range_high = H32(min_range);
> > + min_range_low = L32(min_range);
> > +
> > + /*
> > + * As IIO Val types have no provision for 64 bit values,
> > + * this driver only supports sensors whose minimum range
> > + * reported by SCMI Platform fits within lower 32 bits
> > + */
>
> As discussed in previous thread (after you sent this!) perhaps we just
> need to do the maths in here rather than rely on core handling of IIO_VAL_FRACTIONAL.
> That would give us a greater potential range. There may still be values
> we can't represent, but it should be less restrictive that this
> assumption. (pity as this was neater!)
>
> > + if (min_range_high != 0xFFFFFFFF)
> > + return -EINVAL;
> > +
> > + *val = min_range_low;
> > + *val2 = 1;
> > + }
> > + return 0;
> > +}
> > +
> > +static int scmi_iio_set_sensor_range_avail(struct iio_dev *iio_dev)
> > +{
> > + struct scmi_iio_priv *sensor = iio_priv(iio_dev);
> > + int ret;
> > +
> > + ret = scmi_iio_get_sensor_min_range(iio_dev, &sensor->range_avail[0],
> > + &sensor->range_avail[1]);
> > + if (ret)
> > + return ret;
> > +
> > + scmi_iio_get_sensor_resolution(iio_dev, &sensor->range_avail[2],
> > + &sensor->range_avail[3]);
> > + ret = scmi_iio_get_sensor_max_range(iio_dev, &sensor->range_avail[4],
> > + &sensor->range_avail[5]);
> > + return ret;
> > +}
> > +
> > +static int scmi_iio_set_sampling_freq_avail(struct iio_dev *iio_dev)
> > +{
> > + u64 cur_interval_ns, low_interval_ns, high_interval_ns, step_size_ns,
> > + hz, uhz;
> > + unsigned int cur_interval, low_interval, high_interval, step_size;
> > + struct scmi_iio_priv *sensor = iio_priv(iio_dev);
> > + int i;
> > +
> > + sensor->freq_avail = devm_kzalloc(&iio_dev->dev,
> > + sizeof(u32) * (sensor->sensor_info->intervals.count * 2),
>
> Slight preference for sizeof(*sensor->freq_avail) *...
> as saves reviewer having to go check types match up.
>
> > + GFP_KERNEL);
> > + if (!sensor->freq_avail)
> > + return -ENOMEM;
> > +
> > + if (sensor->sensor_info->intervals.segmented) {
> > + low_interval = sensor->sensor_info->intervals
> > + .desc[SCMI_SENS_INTVL_SEGMENT_LOW];
> > + low_interval_ns = scmi_iio_convert_interval_to_ns(low_interval);
> > + convert_ns_to_freq(low_interval_ns, &hz, &uhz);
> > + sensor->freq_avail[0] = hz;
> > + sensor->freq_avail[1] = uhz;
> > +
> > + step_size = sensor->sensor_info->intervals
> > + .desc[SCMI_SENS_INTVL_SEGMENT_STEP];
> > + step_size_ns = scmi_iio_convert_interval_to_ns(step_size);
> > + convert_ns_to_freq(step_size_ns, &hz, &uhz);
> > + sensor->freq_avail[2] = hz;
> > + sensor->freq_avail[3] = uhz;
> > +
> > + high_interval = sensor->sensor_info->intervals
> > + .desc[SCMI_SENS_INTVL_SEGMENT_HIGH];
> > + high_interval_ns =
> > + scmi_iio_convert_interval_to_ns(high_interval);
> > + convert_ns_to_freq(high_interval_ns, &hz, &uhz);
> > + sensor->freq_avail[4] = hz;
> > + sensor->freq_avail[5] = uhz;
> > + } else {
> > + for (i = 0; i < sensor->sensor_info->intervals.count; i++) {
> > + cur_interval = sensor->sensor_info->intervals.desc[i];
> > + cur_interval_ns = scmi_iio_convert_interval_to_ns(cur_interval);
> > + convert_ns_to_freq(cur_interval_ns, &hz, &uhz);
> > + sensor->freq_avail[i * 2] = hz;
> > + sensor->freq_avail[i * 2 + 1] = uhz;
> > + }
> > + }
> > + return 0;
> > +}
> > +
> > +static int scmi_iio_buffers_setup(struct iio_dev *scmi_iiodev)
> > +{
> > + struct iio_buffer *buffer;
> > +
> > + buffer = devm_iio_kfifo_allocate(&scmi_iiodev->dev);
> > + if (!buffer)
> > + return -ENOMEM;
> > +
> > + iio_device_attach_buffer(scmi_iiodev, buffer);
> > + scmi_iiodev->modes |= INDIO_BUFFER_SOFTWARE;
> > + scmi_iiodev->setup_ops = &scmi_iio_buffer_ops;
> > + return 0;
> > +}
> > +
> > +static int scmi_alloc_iiodev(struct device *dev, struct scmi_handle *handle,
> > + const struct scmi_sensor_info *sensor_info,
> > + struct iio_dev **scmi_iio_dev)
>
> Perhaps it would be nice to use PTR_ERR etc and have this function just return
> the struct iio_dev. That would fit with more common form for allocation functions.
>
> > +{
> > + struct iio_chan_spec *iio_channels;
> > + struct scmi_iio_priv *sensor;
> > + enum iio_modifier modifier;
> > + enum iio_chan_type type;
> > + struct iio_dev *iiodev;
> > + int i, ret;
> > +
> > + iiodev = devm_iio_device_alloc(dev, sizeof(*sensor));
> > + if (!iiodev)
> > + return -ENOMEM;
> > +
> > + iiodev->modes = INDIO_DIRECT_MODE;
> > + iiodev->dev.parent = dev;
> > + sensor = iio_priv(iiodev);
> > + sensor->handle = handle;
> > + sensor->sensor_info = sensor_info;
> > + sensor->sensor_update_nb.notifier_call = scmi_iio_sensor_update_cb;
> > + sensor->indio_dev = iiodev;
> > +
> > + /* adding one additional channel for timestamp */
> > + iiodev->num_channels = sensor_info->num_axis + 1;
> > + iiodev->name = sensor_info->name;
> > + iiodev->info = &scmi_iio_info;
> > +
> > + iio_channels =
> > + devm_kzalloc(dev,
> > + sizeof(*iio_channels) * (iiodev->num_channels),
> > + GFP_KERNEL);
> > + if (!iio_channels)
> > + return -ENOMEM;
> > +
> > + scmi_iio_set_sampling_freq_avail(iiodev);
> > +
> > + ret = scmi_iio_set_sensor_range_avail(iiodev);
> > + if (ret) {
> > + dev_err(dev, "Error while setting the sensor %s range %d",
> > + sensor_info->name, ret);
> > + return ret;
> > + }
> > +
> > + for (i = 0; i < sensor_info->num_axis; i++) {
> > + ret = scmi_iio_get_chan_type(sensor_info->axis[i].type, &type);
> > + if (ret < 0)
> > + return ret;
> > +
> > + ret = scmi_iio_get_chan_modifier(sensor_info->axis[i].name,
> > + &modifier);
> > + if (ret < 0)
> > + return ret;
> > +
> > + scmi_iio_set_data_channel(&iio_channels[i], type, modifier,
> > + sensor_info->axis[i].id);
> > + }
> > +
> > + scmi_iio_set_timestamp_channel(&iio_channels[i], i);
> > + iiodev->channels = iio_channels;
> > + *scmi_iio_dev = iiodev;
> > + return ret;
> > +}
> > +
> > +static int scmi_iio_dev_probe(struct scmi_device *sdev)
> > +{
> > + const struct scmi_sensor_info *sensor_info;
> > + struct scmi_handle *handle = sdev->handle;
> > + struct device *dev = &sdev->dev;
> > + struct iio_dev *scmi_iio_dev;
> > + u16 nr_sensors;
> > + int err, i;
> > +
> > + if (!handle || !handle->sensor_ops) {
> > + dev_err(dev, "SCMI device has no sensor interface\n");
> I'm going to guess we can't actually get here because the registration
> would't have happened if either of those are true?
> If so perhaps drop the error message.
>
> > + return -EINVAL;
> > + }
> > +
> > + nr_sensors = handle->sensor_ops->count_get(handle);
> > + if (!nr_sensors) {
> > + dev_dbg(dev, "0 sensors found via SCMI bus\n");
> -ENODEV maybe?
> > + return -EINVAL;
> > + }
> > +
> > + dev_dbg(dev, "%d sensors found via SCMI bus\n", nr_sensors);
>
> Clear out any debug prints out that don't provide info that can't be obtained
> farily easily from elsewhere. In this case they will either be registered
> or not and we'll get error messages.
> These sort of prints bitrot over time so we want to limit them to the truely
> useful.
>
> > +
> > + for (i = 0; i < nr_sensors; i++) {
> > + sensor_info = handle->sensor_ops->info_get(handle, i);
> > + if (!sensor_info) {
> > + dev_err(dev, "SCMI sensor %d has missing info\n", i);
> > + return -EINVAL;
> > + }
> > +
> > + /* Skipping scalar sensor,as this driver only supports accel and gyro */
> > + if (sensor_info->num_axis == 0)
> > + continue;
>
> So there is a situation where this driver never creates anything? In that path I'd
> like to see an -ENODEV error return.
>
> > +
> > + err = scmi_alloc_iiodev(dev, handle, sensor_info,
> > + &scmi_iio_dev);
> > + if (err < 0) {
> > + dev_err(dev,
> > + "failed to allocate IIO device for sensor %s: %d\n",
> > + sensor_info->name, err);
> > + return err;
> > + }
> > +
> > + err = scmi_iio_buffers_setup(scmi_iio_dev);
> > + if (err < 0) {
> > + dev_err(dev,
> > + "IIO buffer setup error at sensor %s: %d\n",
> > + sensor_info->name, err);
> > + return err;
> > + }
> > +
> > + err = devm_iio_device_register(dev, scmi_iio_dev);
> > + if (err) {
> > + dev_err(dev,
> > + "IIO device registration failed at sensor %s: %d\n",
> > + sensor_info->name, err);
> > + return err;
> > + }
> > + }
> > + return err;
> > +}
> > +
> > +static const struct scmi_device_id scmi_id_table[] = {
> > + { SCMI_PROTOCOL_SENSOR, "iiodev" },
>
> I'm curious on this. What actually causes a match on that
> iiodev? From digging around the scmi core am I right in thinking
> that this iiodev id needs to be explicitly listed?
>
> It would be good to include any changes needed there in this
> series.
>
> > + {},
> > +};
> > +
> > +MODULE_DEVICE_TABLE(scmi, scmi_id_table);
> > +
> > +static struct scmi_driver scmi_iiodev_driver = {
> > + .name = "scmi-sensor-iiodev",
> > + .probe = scmi_iio_dev_probe,
> > + .id_table = scmi_id_table,
> > +};
> > +
> > +module_scmi_driver(scmi_iiodev_driver);
> > +
> > +MODULE_AUTHOR("Jyoti Bhayana <jbhayana@xxxxxxxxxx>");
> > +MODULE_DESCRIPTION("SCMI IIO Driver");
> > +MODULE_LICENSE("GPL v2");
>