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path: root/drivers/iio/temperature/mlx90614.c
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Diffstat (limited to 'drivers/iio/temperature/mlx90614.c')
-rw-r--r--drivers/iio/temperature/mlx90614.c20
1 files changed, 14 insertions, 6 deletions
diff --git a/drivers/iio/temperature/mlx90614.c b/drivers/iio/temperature/mlx90614.c
index e4ec7af4c1bf..5d033a5af615 100644
--- a/drivers/iio/temperature/mlx90614.c
+++ b/drivers/iio/temperature/mlx90614.c
@@ -65,6 +65,13 @@
#define MLX90614_AUTOSLEEP_DELAY 5000 /* default autosleep delay */
+/* Magic constants */
+#define MLX90614_CONST_OFFSET_DEC -13657 /* decimal part of the Kelvin offset */
+#define MLX90614_CONST_OFFSET_REM 500000 /* remainder of offset (273.15*50) */
+#define MLX90614_CONST_SCALE 20 /* Scale in milliKelvin (0.02 * 1000) */
+#define MLX90614_CONST_RAW_EMISSIVITY_MAX 65535 /* max value for emissivity */
+#define MLX90614_CONST_EMISSIVITY_RESOLUTION 15259 /* 1/65535 ~ 0.000015259 */
+
struct mlx90614_data {
struct i2c_client *client;
struct mutex lock; /* for EEPROM access only */
@@ -204,11 +211,11 @@ static int mlx90614_read_raw(struct iio_dev *indio_dev,
*val = ret;
return IIO_VAL_INT;
case IIO_CHAN_INFO_OFFSET:
- *val = -13657;
- *val2 = 500000;
+ *val = MLX90614_CONST_OFFSET_DEC;
+ *val2 = MLX90614_CONST_OFFSET_REM;
return IIO_VAL_INT_PLUS_MICRO;
case IIO_CHAN_INFO_SCALE:
- *val = 20;
+ *val = MLX90614_CONST_SCALE;
return IIO_VAL_INT;
case IIO_CHAN_INFO_CALIBEMISSIVITY: /* 1/65535 / LSB */
mlx90614_power_get(data, false);
@@ -221,12 +228,12 @@ static int mlx90614_read_raw(struct iio_dev *indio_dev,
if (ret < 0)
return ret;
- if (ret == 65535) {
+ if (ret == MLX90614_CONST_RAW_EMISSIVITY_MAX) {
*val = 1;
*val2 = 0;
} else {
*val = 0;
- *val2 = ret * 15259; /* 1/65535 ~ 0.000015259 */
+ *val2 = ret * MLX90614_CONST_EMISSIVITY_RESOLUTION;
}
return IIO_VAL_INT_PLUS_NANO;
default:
@@ -245,7 +252,8 @@ static int mlx90614_write_raw(struct iio_dev *indio_dev,
case IIO_CHAN_INFO_CALIBEMISSIVITY: /* 1/65535 / LSB */
if (val < 0 || val2 < 0 || val > 1 || (val == 1 && val2 != 0))
return -EINVAL;
- val = val * 65535 + val2 / 15259; /* 1/65535 ~ 0.000015259 */
+ val = val * MLX90614_CONST_RAW_EMISSIVITY_MAX +
+ val2 / MLX90614_CONST_EMISSIVITY_RESOLUTION;
mlx90614_power_get(data, false);
mutex_lock(&data->lock);