linux-kernel - Re: [PATCH v5 3/3] iio: light: ltr390: Calculate 'counts_per

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Message-ID: <20240803151327.6212d29b@jic23-huawei>
Date: Sat, 3 Aug 2024 15:13:27 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Abhash Jha <abhashkumarjha123@...il.com>
Cc: linux-iio@...r.kernel.org, anshulusr@...il.com, lars@...afoo.de,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3/3] iio: light: ltr390: Calculate 'counts_per_uvi'
 dynamically

On Wed, 31 Jul 2024 12:07:05 +0530
Abhash Jha <abhashkumarjha123@...il.com> wrote:

> counts_per_uvi depends on the current value of gain and resolution.
> Hence, we cannot use the hardcoded value 96.
> The `counts_per_uvi` function gives the count based on the current gain
> and resolution (integration time).
> 
> Signed-off-by: Abhash Jha <abhashkumarjha123@...il.com>
A few additional minor comments inline as you are doing a v6 anyway.

Thanks,

Jonathan

> ---
>  drivers/iio/light/ltr390.c | 16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/light/ltr390.c b/drivers/iio/light/ltr390.c
> index d3ce43f20..84c084bec 100644
> --- a/drivers/iio/light/ltr390.c
> +++ b/drivers/iio/light/ltr390.c
> @@ -46,6 +46,8 @@
>  #define LTR390_UVS_MODE	      BIT(3)
>  #define LTR390_SENSOR_ENABLE  BIT(1)
>  
> +#define LTR390_FRACTIONAL_PRECISION 100
> +
>  /*
>   * At 20-bit resolution (integration time: 400ms) and 18x gain, 2300 counts of
>   * the sensor are equal to 1 UV Index [Datasheet Page#8].
> @@ -120,6 +122,16 @@ static int ltr390_set_mode(struct ltr390_data *data, enum ltr390_mode mode)
>  	return 0;
>  }
>  
> +static int ltr390_counts_per_uvi(struct ltr390_data *data)
> +{
> +	int orig_gain = 18;
> +	int orig_int_time = 400;

add const to these two.

> +	int divisor = orig_gain * orig_int_time;
I'd use this orig_gain * orig_int_time inline.

> +	int gain = data->gain;

Use this data->gain inline.

> +
> +	return DIV_ROUND_CLOSEST(23 * gain * data->int_time_us, 10 * divisor);
> +}
> +
>  static int ltr390_read_raw(struct iio_dev *iio_device,
>  			   struct iio_chan_spec const *chan, int *val,
>  			   int *val2, long mask)
> @@ -160,8 +172,8 @@ static int ltr390_read_raw(struct iio_dev *iio_device,
>  			if (ret < 0)
>  				return ret;
>  
> -			*val = LTR390_WINDOW_FACTOR;
> -			*val2 = LTR390_COUNTS_PER_UVI;
> +			*val = LTR390_WINDOW_FACTOR * LTR390_FRACTIONAL_PRECISION;
> +			*val2 = ltr390_counts_per_uvi(data);
>  			return IIO_VAL_FRACTIONAL;
>  
>  		case IIO_LIGHT: