staging: iio: cdc: ad7746: Use read_avail() rather than opencoding.

Switch over to the IIO core handling for _available attributes
making them available for in kernel users and enforcing correct
naming etc automatically.
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220626122938.582107-14-jic23@kernel.org

drivers/staging/iio/cdc/ad7746.c

@@ -163,6 +163,7 @@ static const struct iio_chan_spec ad7746_channels[] = {
 		.channel = 0,
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
 		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ),
+		.info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),
 		.address = VIN,
 	},
 	[VIN_VDD] = {
@@ -172,6 +173,7 @@ static const struct iio_chan_spec ad7746_channels[] = {
 		.extend_name = "supply",
 		.info_mask_separate = BIT(IIO_CHAN_INFO_RAW) | BIT(IIO_CHAN_INFO_SCALE),
 		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SAMP_FREQ),
+		.info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),
 		.address = VIN_VDD,
 	},
 	[TEMP_INT] = {
@@ -198,6 +200,7 @@ static const struct iio_chan_spec ad7746_channels[] = {
 		BIT(IIO_CHAN_INFO_CALIBSCALE) | BIT(IIO_CHAN_INFO_OFFSET),
 		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_CALIBBIAS) |
 		BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_SAMP_FREQ),
+		.info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),
 		.address = CIN1,
 	},
 	[CIN1_DIFF] = {
@@ -210,6 +213,7 @@ static const struct iio_chan_spec ad7746_channels[] = {
 		BIT(IIO_CHAN_INFO_CALIBSCALE) | BIT(IIO_CHAN_INFO_ZEROPOINT),
 		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_CALIBBIAS) |
 		BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_SAMP_FREQ),
+		.info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),
 		.address = CIN1_DIFF,
 	},
 	[CIN2] = {
@@ -220,6 +224,7 @@ static const struct iio_chan_spec ad7746_channels[] = {
 		BIT(IIO_CHAN_INFO_CALIBSCALE) | BIT(IIO_CHAN_INFO_OFFSET),
 		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_CALIBBIAS) |
 		BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_SAMP_FREQ),
+		.info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),
 		.address = CIN2,
 	},
 	[CIN2_DIFF] = {
@@ -232,6 +237,7 @@ static const struct iio_chan_spec ad7746_channels[] = {
 		BIT(IIO_CHAN_INFO_CALIBSCALE) | BIT(IIO_CHAN_INFO_ZEROPOINT),
 		.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_CALIBBIAS) |
 		BIT(IIO_CHAN_INFO_SCALE) | BIT(IIO_CHAN_INFO_SAMP_FREQ),
+		.info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_SAMP_FREQ),
 		.address = CIN2_DIFF,
 	}
 };
@@ -440,18 +446,12 @@ static int ad7746_store_vt_filter_rate_setup(struct ad7746_chip_info *chip,
 	return 0;
 }
 
-static IIO_CONST_ATTR(in_voltage_sampling_frequency_available, "50 31 16 8");
-static IIO_CONST_ATTR(in_capacitance_sampling_frequency_available,
-		       "91 84 50 26 16 13 11 9");
-
 static struct attribute *ad7746_attributes[] = {
 	&iio_dev_attr_in_capacitance0_calibbias_calibration.dev_attr.attr,
 	&iio_dev_attr_in_capacitance0_calibscale_calibration.dev_attr.attr,
 	&iio_dev_attr_in_capacitance1_calibscale_calibration.dev_attr.attr,
 	&iio_dev_attr_in_capacitance1_calibbias_calibration.dev_attr.attr,
 	&iio_dev_attr_in_voltage0_calibscale_calibration.dev_attr.attr,
-	&iio_const_attr_in_voltage_sampling_frequency_available.dev_attr.attr,
-	&iio_const_attr_in_capacitance_sampling_frequency_available.dev_attr.attr,
 	NULL,
 };
 
@@ -554,6 +554,32 @@ static int ad7746_write_raw(struct iio_dev *indio_dev,
 	}
 }
 
+static const int ad7746_v_samp_freq[] = { 50, 31, 16, 8, };
+static const int ad7746_cap_samp_freq[] = { 91, 84, 50, 26, 16, 13, 11, 9, };
+
+static int ad7746_read_avail(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan, const int **vals,
+			     int *type, int *length, long mask)
+{
+	if (mask != IIO_CHAN_INFO_SAMP_FREQ)
+		return -EINVAL;
+
+	switch (chan->type) {
+	case IIO_VOLTAGE:
+		*vals = ad7746_v_samp_freq;
+		*length = ARRAY_SIZE(ad7746_v_samp_freq);
+		break;
+	case IIO_CAPACITANCE:
+		*vals = ad7746_cap_samp_freq;
+		*length = ARRAY_SIZE(ad7746_cap_samp_freq);
+		break;
+	default:
+		return -EINVAL;
+	}
+	*type = IIO_VAL_INT;
+	return IIO_AVAIL_LIST;
+}
+
 static int ad7746_read_channel(struct iio_dev *indio_dev,
 			       struct iio_chan_spec const *chan,
 			       int *val)
@@ -689,6 +715,7 @@ static int ad7746_read_raw(struct iio_dev *indio_dev,
 static const struct iio_info ad7746_info = {
 	.attrs = &ad7746_attribute_group,
 	.read_raw = ad7746_read_raw,
+	.read_avail = ad7746_read_avail,
 	.write_raw = ad7746_write_raw,
 };