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.

Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/iio/light/ltr501.c b/drivers/iio/light/ltr501.c
index 64e235281cef7f6703b3b1928953f1eb9b413fb7..1ef7d3773ab90b4ee54dd69656f95899daed0f56 100644 (file)
--- 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 +574,14 @@ 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, \
+}
+
 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 +609,7 @@ 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 +630,23 @@ 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;