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[RFC PATCH 1/2] iio: hmc5843 Add channel attribute for bias configuration

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  [RFC PATCH 1/2] iio: hmc5843 Add channel attribute for bias configuration Cristina Moraru <cristina.moraru09@gmail.com> - 2016-02-04 16:00 +0100
    Re: [RFC PATCH 1/2] iio: hmc5843 Add channel attribute for bias  configuration Lars-Peter Clausen <lars@metafoo.de> - 2016-02-04 18:50 +0100
      Re: [RFC PATCH 1/2] iio: hmc5843 Add channel attribute for bias configuration Daniel Baluta <daniel.baluta@intel.com> - 2016-02-05 11:00 +0100
        Re: [RFC PATCH 1/2] iio: hmc5843 Add channel attribute for bias  configuration Jonathan Cameron <jic23@kernel.org> - 2016-02-06 19:10 +0100
      Re: [RFC PATCH 1/2] iio: hmc5843 Add channel attribute for bias  configuration Jonathan Cameron <jic23@kernel.org> - 2016-02-06 19:10 +0100

#1326898 — [RFC PATCH 1/2] iio: hmc5843 Add channel attribute for bias configuration

Replace non standard meas_conf attribute with the standard IIO
calibbias attribute.

API for setting bias measurement configuration:

0 - Normal measurement configuration (default): In normal measurement
    configuration the device follows normal measurement flow. Pins BP
    and BN are left floating and high impedance.

1 - Positive bias configuration: In positive bias configuration, a
    positive current is forced across the resistive load on pins BP
    and BN.

2 - Negative bias configuration. In negative bias configuration, a
    negative current is forced across the resistive load on pins BP
    and BN.

3 - Only available on HMC5983. Magnetic sensor is disabled.
    Temperature sensor is enabled.

With this in place, we can think of moving this driver out of staging.

Signed-off-by: Cristina Moraru <cristina.moraru09@gmail.com>
---
 drivers/staging/iio/magnetometer/hmc5843_core.c | 62 +++++++------------------
 1 file changed, 16 insertions(+), 46 deletions(-)

diff --git a/drivers/staging/iio/magnetometer/hmc5843_core.c b/drivers/staging/iio/magnetometer/hmc5843_core.c
index 4aab022..c5f16da 100644
--- a/drivers/staging/iio/magnetometer/hmc5843_core.c
+++ b/drivers/staging/iio/magnetometer/hmc5843_core.c
@@ -205,50 +205,6 @@ static int hmc5843_set_meas_conf(struct hmc5843_data *data, u8 meas_conf)
 }
 
 static
-ssize_t hmc5843_show_measurement_configuration(struct device *dev,
-					       struct device_attribute *attr,
-					       char *buf)
-{
-	struct hmc5843_data *data = iio_priv(dev_to_iio_dev(dev));
-	unsigned int val;
-	int ret;
-
-	ret = regmap_read(data->regmap, HMC5843_CONFIG_REG_A, &val);
-	if (ret)
-		return ret;
-	val &= HMC5843_MEAS_CONF_MASK;
-
-	return sprintf(buf, "%d\n", val);
-}
-
-static
-ssize_t hmc5843_set_measurement_configuration(struct device *dev,
-					      struct device_attribute *attr,
-					      const char *buf,
-					      size_t count)
-{
-	struct hmc5843_data *data = iio_priv(dev_to_iio_dev(dev));
-	unsigned long meas_conf = 0;
-	int ret;
-
-	ret = kstrtoul(buf, 10, &meas_conf);
-	if (ret)
-		return ret;
-	if (meas_conf >= HMC5843_MEAS_CONF_MASK)
-		return -EINVAL;
-
-	ret = hmc5843_set_meas_conf(data, meas_conf);
-
-	return (ret < 0) ? ret : count;
-}
-
-static IIO_DEVICE_ATTR(meas_conf,
-			S_IWUSR | S_IRUGO,
-			hmc5843_show_measurement_configuration,
-			hmc5843_set_measurement_configuration,
-			0);
-
-static
 ssize_t hmc5843_show_samp_freq_avail(struct device *dev,
 				     struct device_attribute *attr, char *buf)
 {
@@ -371,6 +327,13 @@ static int hmc5843_read_raw(struct iio_dev *indio_dev,
 		*val = data->variant->regval_to_samp_freq[rval][0];
 		*val2 = data->variant->regval_to_samp_freq[rval][1];
 		return IIO_VAL_INT_PLUS_MICRO;
+	case IIO_CHAN_INFO_CALIBBIAS:
+		ret = regmap_read(data->regmap, HMC5843_CONFIG_REG_A, &rval);
+		if (ret)
+			return ret;
+		rval &= HMC5843_MEAS_CONF_MASK;
+		*val = rval;
+		return IIO_VAL_INT;
 	}
 	return -EINVAL;
 }
@@ -395,6 +358,11 @@ static int hmc5843_write_raw(struct iio_dev *indio_dev,
 			return -EINVAL;
 
 		return hmc5843_set_range_gain(data, range);
+	case IIO_CHAN_INFO_CALIBBIAS:
+		if (val >= HMC5843_MEAS_CONF_MASK)
+			return -EINVAL;
+
+		return hmc5843_set_meas_conf(data, val);
 	default:
 		return -EINVAL;
 	}
@@ -409,6 +377,8 @@ static int hmc5843_write_raw_get_fmt(struct iio_dev *indio_dev,
 		return IIO_VAL_INT_PLUS_MICRO;
 	case IIO_CHAN_INFO_SCALE:
 		return IIO_VAL_INT_PLUS_NANO;
+	case IIO_CHAN_INFO_CALIBBIAS:
+		return IIO_VAL_INT;
 	default:
 		return -EINVAL;
 	}
@@ -451,7 +421,8 @@ done:
 		.channel2 = IIO_MOD_##axis,				\
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
 		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE) |	\
-			BIT(IIO_CHAN_INFO_SAMP_FREQ),			\
+					BIT(IIO_CHAN_INFO_SAMP_FREQ) |  \
+					BIT(IIO_CHAN_INFO_CALIBBIAS),   \
 		.scan_index = idx,					\
 		.scan_type = {						\
 			.sign = 's',					\
@@ -477,7 +448,6 @@ static const struct iio_chan_spec hmc5883_channels[] = {
 };
 
 static struct attribute *hmc5843_attributes[] = {
-	&iio_dev_attr_meas_conf.dev_attr.attr,
 	&iio_dev_attr_scale_available.dev_attr.attr,
 	&iio_dev_attr_sampling_frequency_available.dev_attr.attr,
 	NULL
-- 
1.9.1

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#1327067 — Re: [RFC PATCH 1/2] iio: hmc5843 Add channel attribute for bias configuration

On 02/04/2016 03:50 PM, Cristina Moraru wrote:
> Replace non standard meas_conf attribute with the standard IIO
> calibbias attribute.
> 
> API for setting bias measurement configuration:
> 
> 0 - Normal measurement configuration (default): In normal measurement
>     configuration the device follows normal measurement flow. Pins BP
>     and BN are left floating and high impedance.
> 
> 1 - Positive bias configuration: In positive bias configuration, a
>     positive current is forced across the resistive load on pins BP
>     and BN.
> 
> 2 - Negative bias configuration. In negative bias configuration, a
>     negative current is forced across the resistive load on pins BP
>     and BN.
> 
> 3 - Only available on HMC5983. Magnetic sensor is disabled.
>     Temperature sensor is enabled.
> 
> With this in place, we can think of moving this driver out of staging.

Using a standard attribute, but overloading it with custom semantics doesn't
do any good either. calibbias is supposed to be a integer that gets added to
measurements internally in the device (unit is device specific though).

This attribute seems to do something else. In that case it might be better
to stay with a custom attribute (as long as it is documented) or come up
with a better way to map the device configuration onto standard attributes.

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#1327587

On Thu, Feb 4, 2016 at 7:45 PM, Lars-Peter Clausen <lars@metafoo.de> wrote:
> On 02/04/2016 03:50 PM, Cristina Moraru wrote:
>> Replace non standard meas_conf attribute with the standard IIO
>> calibbias attribute.
>>
>> API for setting bias measurement configuration:
>>
>> 0 - Normal measurement configuration (default): In normal measurement
>>     configuration the device follows normal measurement flow. Pins BP
>>     and BN are left floating and high impedance.
>>
>> 1 - Positive bias configuration: In positive bias configuration, a
>>     positive current is forced across the resistive load on pins BP
>>     and BN.
>>
>> 2 - Negative bias configuration. In negative bias configuration, a
>>     negative current is forced across the resistive load on pins BP
>>     and BN.
>>
>> 3 - Only available on HMC5983. Magnetic sensor is disabled.
>>     Temperature sensor is enabled.
>>
>> With this in place, we can think of moving this driver out of staging.
>
> Using a standard attribute, but overloading it with custom semantics doesn't
> do any good either. calibbias is supposed to be a integer that gets added to
> measurements internally in the device (unit is device specific though).
>
> This attribute seems to do something else. In that case it might be better
> to stay with a custom attribute (as long as it is documented) or come up
> with a better way to map the device configuration onto standard attributes.

We missed the RFC tag. So, with this in mind we still have some minor
issues to fix and then we can move the code out of staging.

1) checkpatch.pl -- strict warnings
2) suspend/resume functions in hmc5843_core.c.

int hmc5843_common_suspend(struct device *dev)
{
        return hmc5843_set_mode(iio_priv(dev_get_drvdata(dev)),
                        HMC5843_MODE_CONVERSION_CONTINUOUS);
}

int hmc5843_common_resume(struct device *dev)
{
        return hmc5843_set_mode(iio_priv(dev_get_drvdata(dev)),
                                HMC5843_MODE_SLEEP);
}

I think the function names or implementations were swapped.
The device should go to sleep at suspend and back to continuous
mode on resume.

thanks,
Daniel.

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#1328343 — Re: [RFC PATCH 1/2] iio: hmc5843 Add channel attribute for bias configuration

On 05/02/16 09:58, Daniel Baluta wrote:
> On Thu, Feb 4, 2016 at 7:45 PM, Lars-Peter Clausen <lars@metafoo.de> wrote:
>> On 02/04/2016 03:50 PM, Cristina Moraru wrote:
>>> Replace non standard meas_conf attribute with the standard IIO
>>> calibbias attribute.
>>>
>>> API for setting bias measurement configuration:
>>>
>>> 0 - Normal measurement configuration (default): In normal measurement
>>>     configuration the device follows normal measurement flow. Pins BP
>>>     and BN are left floating and high impedance.
>>>
>>> 1 - Positive bias configuration: In positive bias configuration, a
>>>     positive current is forced across the resistive load on pins BP
>>>     and BN.
>>>
>>> 2 - Negative bias configuration. In negative bias configuration, a
>>>     negative current is forced across the resistive load on pins BP
>>>     and BN.
>>>
>>> 3 - Only available on HMC5983. Magnetic sensor is disabled.
>>>     Temperature sensor is enabled.
>>>
>>> With this in place, we can think of moving this driver out of staging.
>>
>> Using a standard attribute, but overloading it with custom semantics doesn't
>> do any good either. calibbias is supposed to be a integer that gets added to
>> measurements internally in the device (unit is device specific though).
>>
>> This attribute seems to do something else. In that case it might be better
>> to stay with a custom attribute (as long as it is documented) or come up
>> with a better way to map the device configuration onto standard attributes.
> 
> We missed the RFC tag. So, with this in mind we still have some minor
> issues to fix and then we can move the code out of staging.
> 
> 1) checkpatch.pl -- strict warnings
> 2) suspend/resume functions in hmc5843_core.c.
> 
> int hmc5843_common_suspend(struct device *dev)
> {
>         return hmc5843_set_mode(iio_priv(dev_get_drvdata(dev)),
>                         HMC5843_MODE_CONVERSION_CONTINUOUS);
> }
> 
> int hmc5843_common_resume(struct device *dev)
> {
>         return hmc5843_set_mode(iio_priv(dev_get_drvdata(dev)),
>                                 HMC5843_MODE_SLEEP);
> }
> 
> I think the function names or implementations were swapped.
> The device should go to sleep at suspend and back to continuous
> mode on resume.
Yup, from a quick glance - it otherwise looks sensible to me.
Will as ever attract more reviews once the move out of staging
patch shows up.

Jonathan

> 
> thanks,
> Daniel.
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#1328342 — Re: [RFC PATCH 1/2] iio: hmc5843 Add channel attribute for bias configuration

On 04/02/16 17:45, Lars-Peter Clausen wrote:
> On 02/04/2016 03:50 PM, Cristina Moraru wrote:
>> Replace non standard meas_conf attribute with the standard IIO
>> calibbias attribute.
>>
>> API for setting bias measurement configuration:
>>
>> 0 - Normal measurement configuration (default): In normal measurement
>>     configuration the device follows normal measurement flow. Pins BP
>>     and BN are left floating and high impedance.
>>
>> 1 - Positive bias configuration: In positive bias configuration, a
>>     positive current is forced across the resistive load on pins BP
>>     and BN.
>>
>> 2 - Negative bias configuration. In negative bias configuration, a
>>     negative current is forced across the resistive load on pins BP
>>     and BN.
>>
>> 3 - Only available on HMC5983. Magnetic sensor is disabled.
>>     Temperature sensor is enabled.
>>
>> With this in place, we can think of moving this driver out of staging.
> 
> Using a standard attribute, but overloading it with custom semantics doesn't
> do any good either. calibbias is supposed to be a integer that gets added to
> measurements internally in the device (unit is device specific though).
> 
> This attribute seems to do something else. In that case it might be better
> to stay with a custom attribute (as long as it is documented) or come up
> with a better way to map the device configuration onto standard attributes.
> 
Agree with Lars on this.  Only consistent way that this 'could' (it's not a good idea!)
be supported would be to make this an explicit output channel in a similar way
to we have debated doing with LED drivers in some of the proximity devices.

If it was meant to be a refined compensation of the measured output (perhaps
to correct for some other local field) then perhaps we could argue it as
an analog correction for which calibbias etc would be just about applicable.
Here it's really about self test I think...  One option would be to write
a sane self test entirely in the driver and run that on probe, similar to
we do for some other devices.  Then you could remove this attribute entirely.

Mind you it's not entirely obvious to me what steps the self test would actually
have so perhaps best to leave this to userspace (at least for now!)

Jonathan

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