[PATCH v3] staging: iio: cdc: ad7746: add additional config defines

[Eva Rachel Retuya <eraretuya@gmail.com>]

Introduce defines for shifting and mask under the config register for
better readability. Also, introduce helper variables for index
calculation.

Signed-off-by: Eva Rachel Retuya <eraretuya@gmail.com>
---
This patch might cause a conflict with this patch:
staging: iio: cdc/ad7746: fix missing return value
https://marc.info/?l=linux-driver-devel&m=147741283722806&w=2
I am waiting to rebase to the branch where this commit is present but
I was told it was not yet pushed to kernel.org

Changes in v3:
* Make commit message more detailed.
* Fix incorrect use of GENMASK.
* Drop the AD7746_CONF_*FS(x) macros and use the mask and direct shifting where
  needed.
* With the proper masks set, invert the AND'ng and shifting on the index
  calculations.

Changes in v2:
* Use GENMASK to generate both VTFS and CAPFS masks including offset,
  respectively.
* Introduce helper variables for index calculation.

 drivers/staging/iio/cdc/ad7746.c | 38 ++++++++++++++++++++++----------------
 1 file changed, 22 insertions(+), 16 deletions(-)

diff --git a/drivers/staging/iio/cdc/ad7746.c b/drivers/staging/iio/cdc/ad7746.c
index f41251c..e97658a 100644
--- a/drivers/staging/iio/cdc/ad7746.c
+++ b/drivers/staging/iio/cdc/ad7746.c
@@ -70,8 +70,10 @@
 #define AD7746_EXCSETUP_EXCLVL(x)	(((x) & 0x3) << 0)
 
 /* Config Register Bit Designations (AD7746_REG_CFG) */
-#define AD7746_CONF_VTFS(x)		((x) << 6)
-#define AD7746_CONF_CAPFS(x)		((x) << 3)
+#define AD7746_CONF_VTFS_SHIFT		6
+#define AD7746_CONF_CAPFS_SHIFT		3
+#define AD7746_CONF_VTFS_MASK		GENMASK(7, 6)
+#define AD7746_CONF_CAPFS_MASK		GENMASK(5, 3)
 #define AD7746_CONF_MODE_IDLE		(0 << 0)
 #define AD7746_CONF_MODE_CONT_CONV	(1 << 0)
 #define AD7746_CONF_MODE_SINGLE_CONV	(2 << 0)
@@ -217,15 +219,16 @@ static int ad7746_select_channel(struct iio_dev *indio_dev,
 			    struct iio_chan_spec const *chan)
 {
 	struct ad7746_chip_info *chip = iio_priv(indio_dev);
-	int ret, delay;
+	int ret, delay, idx;
 	u8 vt_setup, cap_setup;
 
 	switch (chan->type) {
 	case IIO_CAPACITANCE:
 		cap_setup = (chan->address & 0xFF) | AD7746_CAPSETUP_CAPEN;
 		vt_setup = chip->vt_setup & ~AD7746_VTSETUP_VTEN;
-		delay = ad7746_cap_filter_rate_table[(chip->config >> 3) &
-			0x7][1];
+		idx = (chip->config & AD7746_CONF_CAPFS_MASK) >>
+			AD7746_CONF_CAPFS_SHIFT;
+		delay = ad7746_cap_filter_rate_table[idx][1];
 
 		if (chip->capdac_set != chan->channel) {
 			ret = i2c_smbus_write_byte_data(chip->client,
@@ -246,8 +249,9 @@ static int ad7746_select_channel(struct iio_dev *indio_dev,
 	case IIO_TEMP:
 		vt_setup = (chan->address & 0xFF) | AD7746_VTSETUP_VTEN;
 		cap_setup = chip->cap_setup & ~AD7746_CAPSETUP_CAPEN;
-		delay = ad7746_cap_filter_rate_table[(chip->config >> 6) &
-			0x3][1];
+		idx = (chip->config & AD7746_CONF_VTFS_MASK) >>
+			AD7746_CONF_VTFS_SHIFT;
+		delay = ad7746_cap_filter_rate_table[idx][1];
 		break;
 	default:
 		return -EINVAL;
@@ -369,8 +373,8 @@ static int ad7746_store_cap_filter_rate_setup(struct ad7746_chip_info *chip,
 	if (i >= ARRAY_SIZE(ad7746_cap_filter_rate_table))
 		i = ARRAY_SIZE(ad7746_cap_filter_rate_table) - 1;
 
-	chip->config &= ~AD7746_CONF_CAPFS(0x7);
-	chip->config |= AD7746_CONF_CAPFS(i);
+	chip->config &= ~AD7746_CONF_CAPFS_MASK;
+	chip->config |= i << AD7746_CONF_CAPFS_SHIFT;
 
 	return 0;
 }
@@ -387,8 +391,8 @@ static int ad7746_store_vt_filter_rate_setup(struct ad7746_chip_info *chip,
 	if (i >= ARRAY_SIZE(ad7746_vt_filter_rate_table))
 		i = ARRAY_SIZE(ad7746_vt_filter_rate_table) - 1;
 
-	chip->config &= ~AD7746_CONF_VTFS(0x3);
-	chip->config |= AD7746_CONF_VTFS(i);
+	chip->config &= ~AD7746_CONF_VTFS_MASK;
+	chip->config |= i << AD7746_CONF_VTFS_SHIFT;
 
 	return 0;
 }
@@ -527,7 +531,7 @@ static int ad7746_read_raw(struct iio_dev *indio_dev,
 			   long mask)
 {
 	struct ad7746_chip_info *chip = iio_priv(indio_dev);
-	int ret, delay;
+	int ret, delay, idx;
 	u8 regval, reg;
 
 	mutex_lock(&indio_dev->mlock);
@@ -635,13 +639,15 @@ static int ad7746_read_raw(struct iio_dev *indio_dev,
 	case IIO_CHAN_INFO_SAMP_FREQ:
 		switch (chan->type) {
 		case IIO_CAPACITANCE:
-			*val = ad7746_cap_filter_rate_table[
-					(chip->config >> 3) & 0x7][0];
+			idx = (chip->config & AD7746_CONF_CAPFS_MASK) >>
+				AD7746_CONF_CAPFS_SHIFT;
+			*val = ad7746_cap_filter_rate_table[idx][0];
 			ret = IIO_VAL_INT;
 			break;
 		case IIO_VOLTAGE:
-			*val = ad7746_vt_filter_rate_table[
-					(chip->config >> 6) & 0x3][0];
+			idx = (chip->config & AD7746_CONF_VTFS_MASK) >>
+				AD7746_CONF_VTFS_SHIFT;
+			*val = ad7746_vt_filter_rate_table[idx][0];
 			break;
 		default:
 			ret = -EINVAL;
-- 
2.7.4