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

Alexandre Belloni
2020-12-09T23:52:06Z

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.belloni@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;
};

--
2.28.0