linux-kernel - Re: [PATCH v2 1/1] iio: ltr501: Add light channel support

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Date:	Fri, 15 May 2015 10:02:52 +0200 (CEST)
From:	Peter Meerwald <pmeerw@...erw.net>
To:	Kuppuswamy Sathyanarayanan 
	<sathyanarayanan.kuppuswamy@...ux.intel.com>
cc:	jic23@...nel.org, linux-iio@...r.kernel.org,
	srinivas.pandruvada@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/1] iio: ltr501: Add light channel support


> Added support to calculate lux value from visible
> and IR spectrum adc count values. Also added IIO_LIGHT
> channel to enable user read the lux value directly
> from device using illuminance input ABI.

minor comment below
 
> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> ---
>  drivers/iio/light/ltr501.c | 57 ++++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 57 insertions(+)
> 
> diff --git a/drivers/iio/light/ltr501.c b/drivers/iio/light/ltr501.c
> index ca4bf47..449b0fd 100644
> --- a/drivers/iio/light/ltr501.c
> +++ b/drivers/iio/light/ltr501.c
> @@ -66,6 +66,9 @@
>  
>  #define LTR501_REGMAP_NAME "ltr501_regmap"
>  
> +#define LTR501_LUX_CONV(vis_coeff, vis_data, ir_coeff, ir_data) \
> +			((vis_coeff * vis_data) - (ir_coeff * ir_data))
> +
>  static const int int_time_mapping[] = {100000, 50000, 200000, 400000};
>  
>  static const struct reg_field reg_field_it =
> @@ -298,6 +301,29 @@ static int ltr501_ps_read_samp_period(struct ltr501_data *data, int *val)
>  	return IIO_VAL_INT;
>  }
>  
> +/* IR and visible spectrum coeff's are given in data sheet */
> +static unsigned long ltr501_calculate_lux(u16 vis_data, u16 ir_data)
> +{
> +	unsigned long ratio, lux;
> +
> +	if (vis_data == 0)
> +		return 0;
> +
> +	/* multiply numerator by 100 to avoid handling ratio < 1 */
> +	ratio = DIV_ROUND_UP(ir_data * 100, ir_data + vis_data);
> +
> +	if (ratio < 45)
> +		lux = LTR501_LUX_CONV(1774, vis_data, -1105, ir_data);
> +	else if (ratio >= 45 && ratio < 64)
> +		lux = LTR501_LUX_CONV(3772, vis_data, 1336, ir_data);
> +	else if (ratio >= 64 && ratio < 85)
> +		lux = LTR501_LUX_CONV(1690, vis_data, 169, ir_data);
> +	else
> +		lux = 0;
> +
> +	return lux / 1000;
> +}
> +
>  static int ltr501_drdy(struct ltr501_data *data, u8 drdy_mask)
>  {
>  	int tries = 100;
> @@ -548,7 +574,20 @@ static const struct iio_event_spec ltr501_pxs_event_spec[] = {
>  	.num_event_specs = _evsize,\
>  }
>  
> +#define LTR501_LIGHT_CHANNEL() { \
> +	.type = IIO_LIGHT, \
> +	.info_mask_separate = BIT(IIO_CHAN_INFO_PROCESSED), \
> +	.scan_index = -1, \

I think there is no need for .scan_type if scan_index == -1

bad examples include: adc/ad7298.c and pressure/st_pressure_core.c


> +	.scan_type = { \
> +		.sign = 'u', \
> +		.realbits = 16, \
> +		.storagebits = 16, \
> +		.endianness = IIO_CPU, \
> +	}, \
> +}
> +
>  static const struct iio_chan_spec ltr501_channels[] = {
> +	LTR501_LIGHT_CHANNEL(),
>  	LTR501_INTENSITY_CHANNEL(0, LTR501_ALS_DATA0, IIO_MOD_LIGHT_BOTH, 0,
>  				 ltr501_als_event_spec,
>  				 ARRAY_SIZE(ltr501_als_event_spec)),
> @@ -576,6 +615,7 @@ static const struct iio_chan_spec ltr501_channels[] = {
>  };
>  
>  static const struct iio_chan_spec ltr301_channels[] = {
> +	LTR501_LIGHT_CHANNEL(),
>  	LTR501_INTENSITY_CHANNEL(0, LTR501_ALS_DATA0, IIO_MOD_LIGHT_BOTH, 0,
>  				 ltr501_als_event_spec,
>  				 ARRAY_SIZE(ltr501_als_event_spec)),
> @@ -596,6 +636,23 @@ static int ltr501_read_raw(struct iio_dev *indio_dev,
>  	int ret, i;
>  
>  	switch (mask) {
> +	case IIO_CHAN_INFO_PROCESSED:
> +		if (iio_buffer_enabled(indio_dev))
> +			return -EBUSY;
> +
> +		switch (chan->type) {
> +		case IIO_LIGHT:
> +			mutex_lock(&data->lock_als);
> +			ret = ltr501_read_als(data, buf);
> +			mutex_unlock(&data->lock_als);
> +			if (ret < 0)
> +				return ret;
> +			*val = ltr501_calculate_lux(le16_to_cpu(buf[1]),
> +						    le16_to_cpu(buf[0]));
> +			return IIO_VAL_INT;
> +		default:
> +			return -EINVAL;
> +		}
>  	case IIO_CHAN_INFO_RAW:
>  		if (iio_buffer_enabled(indio_dev))
>  			return -EBUSY;
> 

-- 

Peter Meerwald
+43-664-2444418 (mobile)
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