[PATCH] iio: adc: nau7802: Expose possible gains in sysfs

[PATCH] iio: adc: nau7802: Expose possible gains in sysfs

[Quentin Schulz]

The Nuvoton NAU7802 ADC is able to adjust its gain but prior knowledge of
its possible values was required to adjust it. Users had to guess the
possible gain values based on the ADC datasheet or on this driver's code.

This exposes the possible values in the in_voltage_scale_available file of
each nau7802 ADC device. The gain is set for the whole ADC and is therefore
not configurable by channel. Thus, there exists only one
in_voltage_scale_available file for each nau7802 ADC device even if it has
two separate channels.

Signed-off-by: Quentin Schulz <quentin.schulz@free-electrons.com>
---

There exists two files to set the gain: in_voltageX_scale_available and
in_voltage-voltage_scale_available. What are the differences between those
two? What are the use cases for each? Which one should I have used?

 drivers/iio/adc/nau7802.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/drivers/iio/adc/nau7802.c b/drivers/iio/adc/nau7802.c
index e525aa6..57365c5 100644
--- a/drivers/iio/adc/nau7802.c
+++ b/drivers/iio/adc/nau7802.c
@@ -79,10 +79,29 @@ static const struct iio_chan_spec nau7802_chan_array[] = {
 static const u16 nau7802_sample_freq_avail[] = {10, 20, 40, 80,
 						10, 10, 10, 320};
 
+static ssize_t nau7802_show_scales(struct device *dev,
+				   struct device_attribute *attr, char *buf)
+{
+	struct nau7802_state *st = iio_priv(dev_to_iio_dev(dev));
+	int i, len = 0;
+
+	for (i = 0; i < ARRAY_SIZE(st->scale_avail); i++)
+		len += scnprintf(buf + len, PAGE_SIZE - len, "0.%09d ",
+				 st->scale_avail[i]);
+
+	buf[len-1] = '\n';
+
+	return len;
+}
+
 static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("10 40 80 320");
 
+static IIO_DEVICE_ATTR(in_voltage_scale_available, S_IRUGO, nau7802_show_scales,
+		       NULL, 0);
+
 static struct attribute *nau7802_attributes[] = {
 	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
+	&iio_dev_attr_in_voltage_scale_available.dev_attr.attr,
 	NULL
 };
 
-- 
2.5.0

Re: [PATCH] iio: adc: nau7802: Expose possible gains in sysfs

[Daniel Baluta]

On Wed, May 18, 2016 at 6:16 PM, Quentin Schulz
<quentin.schulz@free-electrons.com> wrote:
> The Nuvoton NAU7802 ADC is able to adjust its gain but prior knowledge of
> its possible values was required to adjust it. Users had to guess the
> possible gain values based on the ADC datasheet or on this driver's code.
>
> This exposes the possible values in the in_voltage_scale_available file of
> each nau7802 ADC device. The gain is set for the whole ADC and is therefore
> not configurable by channel. Thus, there exists only one
> in_voltage_scale_available file for each nau7802 ADC device even if it has
> two separate channels.
>
> Signed-off-by: Quentin Schulz <quentin.schulz@free-electrons.com>
> ---
>
> There exists two files to set the gain: in_voltageX_scale_available and
> in_voltage-voltage_scale_available. What are the differences between those
> two? What are the use cases for each? Which one should I have used?

First is for single channels while the latter is for differential channels.
In this case it's correct to use in in_voltageX_scale_available as you did.

thanks,
Daniel.

Re: [PATCH] iio: adc: nau7802: Expose possible gains in sysfs

[Alexandre Belloni]

On 18/05/2016 at 17:16:18 +0200, Quentin Schulz wrote :
>
> The Nuvoton NAU7802 ADC is able to adjust its gain but prior knowledge of
> its possible values was required to adjust it. Users had to guess the
> possible gain values based on the ADC datasheet or on this driver's code.
> 
> This exposes the possible values in the in_voltage_scale_available file of
> each nau7802 ADC device. The gain is set for the whole ADC and is therefore
> not configurable by channel. Thus, there exists only one
> in_voltage_scale_available file for each nau7802 ADC device even if it has
> two separate channels.
> 
> Signed-off-by: Quentin Schulz <quentin.schulz@free-electrons.com>
Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>

> ---
> 
> There exists two files to set the gain: in_voltageX_scale_available and
> in_voltage-voltage_scale_available. What are the differences between those
> two? What are the use cases for each? Which one should I have used?
> 
>  drivers/iio/adc/nau7802.c | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/drivers/iio/adc/nau7802.c b/drivers/iio/adc/nau7802.c
> index e525aa6..57365c5 100644
> --- a/drivers/iio/adc/nau7802.c
> +++ b/drivers/iio/adc/nau7802.c
> @@ -79,10 +79,29 @@ static const struct iio_chan_spec nau7802_chan_array[] = {
>  static const u16 nau7802_sample_freq_avail[] = {10, 20, 40, 80,
>  						10, 10, 10, 320};
>  
> +static ssize_t nau7802_show_scales(struct device *dev,
> +				   struct device_attribute *attr, char *buf)
> +{
> +	struct nau7802_state *st = iio_priv(dev_to_iio_dev(dev));
> +	int i, len = 0;
> +
> +	for (i = 0; i < ARRAY_SIZE(st->scale_avail); i++)
> +		len += scnprintf(buf + len, PAGE_SIZE - len, "0.%09d ",
> +				 st->scale_avail[i]);
> +
> +	buf[len-1] = '\n';
> +
> +	return len;
> +}
> +
>  static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("10 40 80 320");
>  
> +static IIO_DEVICE_ATTR(in_voltage_scale_available, S_IRUGO, nau7802_show_scales,
> +		       NULL, 0);
> +
>  static struct attribute *nau7802_attributes[] = {
>  	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
> +	&iio_dev_attr_in_voltage_scale_available.dev_attr.attr,
>  	NULL
>  };
>  
> -- 
> 2.5.0
> 

-- 
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com

Re: [PATCH] iio: adc: nau7802: Expose possible gains in sysfs

[Jonathan Cameron]

On 19/05/16 11:01, Alexandre Belloni wrote:
> On 18/05/2016 at 17:16:18 +0200, Quentin Schulz wrote :
>>
>> The Nuvoton NAU7802 ADC is able to adjust its gain but prior knowledge of
>> its possible values was required to adjust it. Users had to guess the
>> possible gain values based on the ADC datasheet or on this driver's code.
>>
>> This exposes the possible values in the in_voltage_scale_available file of
>> each nau7802 ADC device. The gain is set for the whole ADC and is therefore
>> not configurable by channel. Thus, there exists only one
>> in_voltage_scale_available file for each nau7802 ADC device even if it has
>> two separate channels.
>>
>> Signed-off-by: Quentin Schulz <quentin.schulz@free-electrons.com>
> Acked-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>
Applied to the togreg branch of iio.git - initially pushed out as testing
for the autobuilders to play with it.

Thanks,

Jonathan
> 
>> ---
>>
>> There exists two files to set the gain: in_voltageX_scale_available and
>> in_voltage-voltage_scale_available. What are the differences between those
>> two? What are the use cases for each? Which one should I have used?
>>
>>  drivers/iio/adc/nau7802.c | 19 +++++++++++++++++++
>>  1 file changed, 19 insertions(+)
>>
>> diff --git a/drivers/iio/adc/nau7802.c b/drivers/iio/adc/nau7802.c
>> index e525aa6..57365c5 100644
>> --- a/drivers/iio/adc/nau7802.c
>> +++ b/drivers/iio/adc/nau7802.c
>> @@ -79,10 +79,29 @@ static const struct iio_chan_spec nau7802_chan_array[] = {
>>  static const u16 nau7802_sample_freq_avail[] = {10, 20, 40, 80,
>>  						10, 10, 10, 320};
>>  
>> +static ssize_t nau7802_show_scales(struct device *dev,
>> +				   struct device_attribute *attr, char *buf)
>> +{
>> +	struct nau7802_state *st = iio_priv(dev_to_iio_dev(dev));
>> +	int i, len = 0;
>> +
>> +	for (i = 0; i < ARRAY_SIZE(st->scale_avail); i++)
>> +		len += scnprintf(buf + len, PAGE_SIZE - len, "0.%09d ",
>> +				 st->scale_avail[i]);
>> +
>> +	buf[len-1] = '\n';
>> +
>> +	return len;
>> +}
>> +
>>  static IIO_CONST_ATTR_SAMP_FREQ_AVAIL("10 40 80 320");
>>  
>> +static IIO_DEVICE_ATTR(in_voltage_scale_available, S_IRUGO, nau7802_show_scales,
>> +		       NULL, 0);
>> +
>>  static struct attribute *nau7802_attributes[] = {
>>  	&iio_const_attr_sampling_frequency_available.dev_attr.attr,
>> +	&iio_dev_attr_in_voltage_scale_available.dev_attr.attr,
>>  	NULL
>>  };
>>  
>> -- 
>> 2.5.0
>>
>