Re: [PATCH] iio: light: veml6075: fix UV index reported at half value

[Javier Carrasco]

On Fri Jun 26, 2026 at 1:04 PM CEST, Shardul Deshpande wrote:
> veml6075_get_uvi_micro() normalises the UV index for the configured
> integration time by dividing the summed, responsivity-weighted UVA/UVB
> components by the integration-time scale factor relative to the 50 ms
> base case (which is returned undivided).
>
> The supported integration times are 50, 100, 200, 400 and 800 ms, i.e.
> the register field index int_index in 0..4 selects (50 << int_index) ms,
> so the correct scale factor is 2^int_index == (1 << int_index).
>
> The code instead divides by (2 << int_index) == 2^(int_index + 1), which
> is twice the correct value. The reported UV index is therefore half of
> the true value for every integration time except 50 ms (handled as a
> separate case). As the driver powers up with VEML6075_IT_100_MS, the UV
> index is reported at half value out of the box.
>
> Divide by (1 << int_index) instead; this also matches the undivided
> 50 ms case (1 << 0 == 1).
>
> Fixes: 3b82f43238ae ("iio: light: add VEML6075 UVA and UVB light sensor driver")
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: Shardul Deshpande <iamsharduld@xxxxxxxxx>
> ---
>  drivers/iio/light/veml6075.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/iio/light/veml6075.c b/drivers/iio/light/veml6075.c
> index 59187244a..af71df69f 100644
> --- a/drivers/iio/light/veml6075.c
> +++ b/drivers/iio/light/veml6075.c
> @@ -244,7 +244,7 @@ static int veml6075_get_uvi_micro(struct veml6075_data *data, int uva_comp,
>  	case VEML6075_IT_200_MS:
>  	case VEML6075_IT_400_MS:
>  	case VEML6075_IT_800_MS:
> -		return (uvia_micro + uvib_micro) / (2 << int_index);
> +		return (uvia_micro + uvib_micro) / (1 << int_index);
>  	default:
>  		return -EINVAL;
>  	}

Hi Shardul, thank you for your patch.

I agree with your reasoning, but why don't you get rid of the switch
once the operation is the same for all cases?

Best regards,
Javier