iio: potentiometer: ds1803: Add available functionality

Adding available functionality for DS1803 driver which
will show the minimum, step and maximum values that the
driver can accepts through sysfs entry.
Now using the max value present in avail array instead of chip
type specific macro to make the driver flexible to add other
type of potentiometer with different max position value.
Signed-off-by: Jagath Jog J <jagathjog1996@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20220223163525.13399-3-jagathjog1996@gmail.comSigned-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/potentiometer/ds1803.c

@@ -16,7 +16,6 @@
 #include <linux/module.h>
 #include <linux/mod_devicetable.h>
 
-#define DS1803_MAX_POS		255
 #define DS1803_WRITE(chan)	(0xa8 | ((chan) + 1))
 
 enum ds1803_type {
@@ -26,27 +25,23 @@ enum ds1803_type {
 };
 
 struct ds1803_cfg {
+	int avail[3];
 	int kohms;
 };
 
-static const struct ds1803_cfg ds1803_cfg[] = {
-	[DS1803_010] = { .kohms =  10, },
-	[DS1803_050] = { .kohms =  50, },
-	[DS1803_100] = { .kohms = 100, },
-};
-
 struct ds1803_data {
 	struct i2c_client *client;
 	const struct ds1803_cfg *cfg;
 };
 
-#define DS1803_CHANNEL(ch) {					\
-	.type = IIO_RESISTANCE,					\
-	.indexed = 1,						\
-	.output = 1,						\
-	.channel = (ch),					\
-	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),		\
-	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),	\
+#define DS1803_CHANNEL(ch) {						\
+	.type = IIO_RESISTANCE,						\
+	.indexed = 1,							\
+	.output = 1,							\
+	.channel = (ch),						\
+	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),			\
+	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),		\
+	.info_mask_shared_by_type_available = BIT(IIO_CHAN_INFO_RAW),   \
 }
 
 static const struct iio_chan_spec ds1803_channels[] = {
@@ -54,6 +49,21 @@ static const struct iio_chan_spec ds1803_channels[] = {
 	DS1803_CHANNEL(1),
 };
 
+static const struct ds1803_cfg ds1803_cfg[] = {
+	[DS1803_010] = {
+		.avail = { 0, 1, 255 },
+		.kohms =  10,
+	},
+	[DS1803_050] = {
+		.avail = { 0, 1, 255 },
+		.kohms =  50,
+	},
+	[DS1803_100] = {
+		.avail = { 0, 1, 255 },
+		.kohms = 100,
+	},
+};
+
 static int ds1803_read_raw(struct iio_dev *indio_dev,
 			   struct iio_chan_spec const *chan,
 			   int *val, int *val2, long mask)
@@ -75,7 +85,7 @@ static int ds1803_read_raw(struct iio_dev *indio_dev,
 
 	case IIO_CHAN_INFO_SCALE:
 		*val = 1000 * data->cfg->kohms;
-		*val2 = DS1803_MAX_POS;
+		*val2 = data->cfg->avail[2]; /* Max wiper position */
 		return IIO_VAL_FRACTIONAL;
 	}
 
@@ -88,13 +98,14 @@ static int ds1803_write_raw(struct iio_dev *indio_dev,
 {
 	struct ds1803_data *data = iio_priv(indio_dev);
 	int pot = chan->channel;
+	int max_pos = data->cfg->avail[2];
 
 	if (val2 != 0)
 		return -EINVAL;
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
-		if (val > DS1803_MAX_POS || val < 0)
+		if (val > max_pos || val < 0)
 			return -EINVAL;
 		break;
 	default:
@@ -104,9 +115,27 @@ static int ds1803_write_raw(struct iio_dev *indio_dev,
 	return i2c_smbus_write_byte_data(data->client, DS1803_WRITE(pot), val);
 }
 
+static int ds1803_read_avail(struct iio_dev *indio_dev,
+			     struct iio_chan_spec const *chan,
+			     const int **vals, int *type,
+			     int *length, long mask)
+{
+	struct ds1803_data *data = iio_priv(indio_dev);
+
+	switch (mask) {
+	case IIO_CHAN_INFO_RAW:
+		*vals = data->cfg->avail;
+		*length = ARRAY_SIZE(data->cfg->avail);
+		*type = IIO_VAL_INT;
+		return IIO_AVAIL_RANGE;
+	}
+	return -EINVAL;
+}
+
 static const struct iio_info ds1803_info = {
 	.read_raw = ds1803_read_raw,
 	.write_raw = ds1803_write_raw,
+	.read_avail = ds1803_read_avail,
 };
 
 static int ds1803_probe(struct i2c_client *client, const struct i2c_device_id *id)