> Translates the magic constant numbers to named macros and add some
> additional comments about their meaning. Also changed the offset to
> negative as usual equation is: (raw + offset)*scale and in this
> case offset should be negative (as we deduct 273.15 Kelvin to get
> temperature in Celsius).
looks good; strictly, this patch is
(a) a bugfix (the offset should be negative),
(b) cleanup to replace constants by macros
> The diff is made towards togreg branch as that branch seems to have the
> most recent updates of mlx90614 driver (many are yet to be merged).
>
> Signed-off-by: Crt Mori <cmo@xxxxxxxxxxx>
> ---
> drivers/iio/temperature/mlx90614.c | 20 ++++++++++++++------
> 1 file changed, 14 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/iio/temperature/mlx90614.c
> b/drivers/iio/temperature/mlx90614.c
> index cb2e8ad..909278a 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);
>
--
Peter Meerwald
+43-664-2444418 (mobile)
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