[PATCH v2 4/6] iio:common:ms_sensors:ms_sensors_i2c: rework CRC calculation helper

[Alexandre Belloni]

The CRC calculation always happens on 8 words which is why there is an
extra element in the prom array of struct ms_tp_dev. However, on ms5637 and
similar, only 7 words are readable.

Then, set MS_SENSORS_TP_PROM_WORDS_NB to 8 and stop passing a len parameter
to ms_sensors_tp_crc_valid as this simply hide the fact that it is
hardcoded.

Finally, use the newly introduced hw->prom_len to know how many words can be
read.

Signed-off-by: Alexandre Belloni <alexandre.bell...@bootlin.com>
---
 drivers/iio/common/ms_sensors/ms_sensors_i2c.c | 12 +++++-------
 drivers/iio/common/ms_sensors/ms_sensors_i2c.h |  4 ++--
 2 files changed, 7 insertions(+), 9 deletions(-)

diff --git a/drivers/iio/common/ms_sensors/ms_sensors_i2c.c 
b/drivers/iio/common/ms_sensors/ms_sensors_i2c.c
index b9e2038d05ef..872f90459e2e 100644
--- a/drivers/iio/common/ms_sensors/ms_sensors_i2c.c
+++ b/drivers/iio/common/ms_sensors/ms_sensors_i2c.c
@@ -493,19 +493,18 @@ EXPORT_SYMBOL(ms_sensors_ht_read_humidity);
  *     This function is only used when reading PROM coefficients
  *
  * @prom:      pointer to PROM coefficients array
- * @len:       length of PROM coefficients array
  *
  * Return: True if CRC is ok.
  */
-static bool ms_sensors_tp_crc_valid(u16 *prom, u8 len)
+static bool ms_sensors_tp_crc_valid(u16 *prom)
 {
        unsigned int cnt, n_bit;
        u16 n_rem = 0x0000, crc_read = prom[0], crc = (*prom & 0xF000) >> 12;
 
-       prom[len - 1] = 0;
+       prom[MS_SENSORS_TP_PROM_WORDS_NB - 1] = 0;
        prom[0] &= 0x0FFF;      /* Clear the CRC computation part */
 
-       for (cnt = 0; cnt < len * 2; cnt++) {
+       for (cnt = 0; cnt < MS_SENSORS_TP_PROM_WORDS_NB * 2; cnt++) {
                if (cnt % 2 == 1)
                        n_rem ^= prom[cnt >> 1] & 0x00FF;
                else
@@ -537,7 +536,7 @@ int ms_sensors_tp_read_prom(struct ms_tp_dev *dev_data)
 {
        int i, ret;
 
-       for (i = 0; i < MS_SENSORS_TP_PROM_WORDS_NB; i++) {
+       for (i = 0; i < dev_data->hw->prom_len; i++) {
                ret = ms_sensors_read_prom_word(
                        dev_data->client,
                        MS_SENSORS_TP_PROM_READ + (i << 1),
@@ -547,8 +546,7 @@ int ms_sensors_tp_read_prom(struct ms_tp_dev *dev_data)
                        return ret;
        }
 
-       if (!ms_sensors_tp_crc_valid(dev_data->prom,
-                                    MS_SENSORS_TP_PROM_WORDS_NB + 1)) {
+       if (!ms_sensors_tp_crc_valid(dev_data->prom)) {
                dev_err(&dev_data->client->dev,
                        "Calibration coefficients crc check error\n");
                return -ENODEV;
diff --git a/drivers/iio/common/ms_sensors/ms_sensors_i2c.h 
b/drivers/iio/common/ms_sensors/ms_sensors_i2c.h
index f4a88148c113..f15b973f27c6 100644
--- a/drivers/iio/common/ms_sensors/ms_sensors_i2c.h
+++ b/drivers/iio/common/ms_sensors/ms_sensors_i2c.h
@@ -11,7 +11,7 @@
 #include <linux/i2c.h>
 #include <linux/mutex.h>
 
-#define MS_SENSORS_TP_PROM_WORDS_NB            7
+#define MS_SENSORS_TP_PROM_WORDS_NB            8
 
 /**
  * struct ms_ht_dev - Humidity/Temperature sensor device structure
@@ -47,7 +47,7 @@ struct ms_tp_dev {
        struct i2c_client *client;
        struct mutex lock;
        const struct ms_tp_hw_data *hw;
-       u16 prom[MS_SENSORS_TP_PROM_WORDS_NB + 1];
+       u16 prom[MS_SENSORS_TP_PROM_WORDS_NB];
        u8 res_index;
 };
 
-- 
2.29.2