staging: iio: adt7316: change interpretation of write to dac update mode

Based on the output of adt7316_show_all_DAC_update_modes() and
adt7316_show_DAC_update_mode(), adt7316_store_DAC_update_mode() should
expect the user to enter an integer input from 0 to 3. The user input is
currently expected to account for the actual bit positions in the register.
For example, choosing option 3 would require a write of 0x30 (actually 48
since it expects base 10). To address this inconsistency, create a shift
macro to be used in the valid input check as well as the calculation for
the register write.
Signed-off-by: Jeremy Fertic <jeremyfertic@gmail.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

drivers/staging/iio/addac/adt7316.c

@@ -127,6 +127,7 @@
  */
 #define ADT7316_DA_2VREF_CH_MASK	0xF
 #define ADT7316_DA_EN_MODE_MASK		0x30
+#define ADT7316_DA_EN_MODE_SHIFT	4
 #define ADT7316_DA_EN_MODE_SINGLE	0x00
 #define ADT7316_DA_EN_MODE_AB_CD	0x10
 #define ADT7316_DA_EN_MODE_ABCD		0x20
@@ -884,11 +885,11 @@ static ssize_t adt7316_store_DAC_update_mode(struct device *dev,
 		return -EPERM;
 
 	ret = kstrtou8(buf, 10, &data);
-	if (ret || data > ADT7316_DA_EN_MODE_MASK)
+	if (ret || data > (ADT7316_DA_EN_MODE_MASK >> ADT7316_DA_EN_MODE_SHIFT))
 		return -EINVAL;
 
 	dac_config = chip->dac_config & (~ADT7316_DA_EN_MODE_MASK);
-	dac_config |= data;
+	dac_config |= data << ADT7316_DA_EN_MODE_SHIFT;
 
 	ret = chip->bus.write(chip->bus.client, ADT7316_DAC_CONFIG, dac_config);
 	if (ret)