iio: adc: ad9467: fix scale setting

[ Upstream commit b73f08bb7f ]

When reading in_voltage_scale we can get something like:

root@analog:/sys/bus/iio/devices/iio:device2# cat in_voltage_scale
0.038146

However, when reading the available options:

root@analog:/sys/bus/iio/devices/iio:device2# cat
in_voltage_scale_available
2000.000000 2100.000006 2200.000007 2300.000008 2400.000009 2500.000010

which does not make sense. Moreover, when trying to set a new scale we
get an error because there's no call to __ad9467_get_scale() to give us
values as given when reading in_voltage_scale. Fix it by computing the
available scales during probe and properly pass the list when
.read_available() is called.

While at it, change to use .read_available() from iio_info. Also note
that to properly fix this, adi-axi-adc.c has to be changed accordingly.

Fixes: ad67971202 ("iio: adc: ad9467: add support AD9467 ADC")
Signed-off-by: Nuno Sa <nuno.sa@analog.com>
Reviewed-by: David Lechner <dlechner@baylibre.com>
Link: https://lore.kernel.org/r/20231207-iio-backend-prep-v2-4-a4a33bc4d70e@analog.com
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

include/linux/iio/adc/adi-axi-adc.h

@@ -41,6 +41,7 @@ struct adi_axi_adc_chip_info {
  * @reg_access		IIO debugfs_reg_access hook for the client ADC
  * @read_raw		IIO read_raw hook for the client ADC
  * @write_raw		IIO write_raw hook for the client ADC
+ * @read_avail		IIO read_avail hook for the client ADC
  */
 struct adi_axi_adc_conv {
 	const struct adi_axi_adc_chip_info		*chip_info;
@@ -54,6 +55,9 @@ struct adi_axi_adc_conv {
 	int (*write_raw)(struct adi_axi_adc_conv *conv,
 			 struct iio_chan_spec const *chan,
 			 int val, int val2, long mask);
+	int (*read_avail)(struct adi_axi_adc_conv *conv,
+			  struct iio_chan_spec const *chan,
+			  const int **val, int *type, int *length, long mask);
 };
 
 struct adi_axi_adc_conv *devm_adi_axi_adc_conv_register(struct device *dev,