iio: accel: adxl345: convert address field usage in iio_chan_spec

Currently the address field in iio_chan_spec is filled with an accel
data register address for the corresponding axis.

In preparation for adding calibration offset support, this sets the
address field to the index of accel data registers instead of the actual
register address.

This change makes it easier to access both accel registers and
calibration offset registers with fewer lines of code as these are
located in X-axis, Y-axis, Z-axis order.

Cc: Eva Rachel Retuya <eraretuya@gmail.com>
Cc: Andy Shevchenko <andy.shevchenko@gmail.com>
Cc: Jonathan Cameron <jic23@kernel.org>
Signed-off-by: Akinobu Mita <akinobu.mita@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/iio/accel/adxl345_core.c

@@ -23,6 +23,8 @@
 #define ADXL345_REG_DATAX0		0x32
 #define ADXL345_REG_DATAY0		0x34
 #define ADXL345_REG_DATAZ0		0x36
+#define ADXL345_REG_DATA_AXIS(index)	\
+	(ADXL345_REG_DATAX0 + (index) * sizeof(__le16))
 
 #define ADXL345_POWER_CTL_MEASURE	BIT(3)
 #define ADXL345_POWER_CTL_STANDBY	0x00
@@ -49,19 +51,19 @@ struct adxl345_data {
 	u8 data_range;
 };
 
-#define ADXL345_CHANNEL(reg, axis) {					\
+#define ADXL345_CHANNEL(index, axis) {					\
 	.type = IIO_ACCEL,						\
 	.modified = 1,							\
 	.channel2 = IIO_MOD_##axis,					\
-	.address = reg,							\
+	.address = index,						\
 	.info_mask_separate = BIT(IIO_CHAN_INFO_RAW),			\
 	.info_mask_shared_by_type = BIT(IIO_CHAN_INFO_SCALE),		\
 }
 
 static const struct iio_chan_spec adxl345_channels[] = {
-	ADXL345_CHANNEL(ADXL345_REG_DATAX0, X),
-	ADXL345_CHANNEL(ADXL345_REG_DATAY0, Y),
-	ADXL345_CHANNEL(ADXL345_REG_DATAZ0, Z),
+	ADXL345_CHANNEL(0, X),
+	ADXL345_CHANNEL(1, Y),
+	ADXL345_CHANNEL(2, Z),
 };
 
 static int adxl345_read_raw(struct iio_dev *indio_dev,
@@ -69,7 +71,7 @@ static int adxl345_read_raw(struct iio_dev *indio_dev,
 			    int *val, int *val2, long mask)
 {
 	struct adxl345_data *data = iio_priv(indio_dev);
-	__le16 regval;
+	__le16 accel;
 	int ret;
 
 	switch (mask) {
@@ -79,12 +81,13 @@ static int adxl345_read_raw(struct iio_dev *indio_dev,
 		 * ADXL345_REG_DATA(X0/Y0/Z0) contain the least significant byte
 		 * and ADXL345_REG_DATA(X0/Y0/Z0) + 1 the most significant byte
 		 */
-		ret = regmap_bulk_read(data->regmap, chan->address, &regval,
-				       sizeof(regval));
+		ret = regmap_bulk_read(data->regmap,
+				       ADXL345_REG_DATA_AXIS(chan->address),
+				       &accel, sizeof(accel));
 		if (ret < 0)
 			return ret;
 
-		*val = sign_extend32(le16_to_cpu(regval), 12);
+		*val = sign_extend32(le16_to_cpu(accel), 12);
 		return IIO_VAL_INT;
 	case IIO_CHAN_INFO_SCALE:
 		*val = 0;