iio: adc: nau7802: Expose possible gains in sysfs

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>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/adc/nau7802.c b/drivers/iio/adc/nau7802.c
index e525aa6475c42b20cef6f3653da973620a2bccc9..57365c504093d993e5f09a34b6fa50e82f586a26 100644 (file)
--- 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
 };