S5PC11X: SENSOR: Change LightSensor to return lux

Our initial LightSensor HAL returned the raw adc from the driver.
Now we implement an initial conversion from adc to lux levels.
It's not perfect, but lux varies quite a bit anyway and the levels
are so large that precision isn't generally as important as being
in the right ballpark.  We can ask HW team to do get more precision
if necessary.

Change-Id: I7ad09bb13831b8100c255ab9cd7287a4b684619d
Signed-off-by: Mike J. Chen <mjchen@sta.samsung.com>

1 files changed, 22 insertions, 8 deletions

diff --git a/libsensors/LightSensor.cpp b/libsensors/LightSensor.cpp
index 087afb4..fa08685 100644
--- a/libsensors/LightSensor.cpp
+++ b/libsensors/LightSensor.cpp
@@ -131,10 +131,7 @@ int LightSensor::readEvents(sensors_event_t* data, int count)
         int type = event->type;
         if (type == EV_ABS) {
             if (event->code == EVENT_TYPE_LIGHT) {
-                if (event->value != -1) {
-                    // FIXME: not sure why we're getting -1 sometimes
-                    mPendingEvent.light = indexToValue(event->value);
-                }
+                mPendingEvent.light = indexToValue(event->value);
             }
         } else if (type == EV_SYN) {
             mPendingEvent.timestamp = timevalToNano(event->time);
@@ -155,8 +152,25 @@ int LightSensor::readEvents(sensors_event_t* data, int count)
 
 float LightSensor::indexToValue(size_t index) const
 {
-#warning Return lux levels
-    /* for now we return just raw ADC levels.  need to convert
-       to lux levels.  tbd. */
-    return index;
+    /* Driver gives a rolling average adc value.  We convert it lux levels. */
+    static const struct adcToLux {
+        size_t adc_value;
+        float  lux_value;
+    } adcToLux[] = {
+        {  150,   10.0 },  /* from    0 -  150 adc, we map to    10.0 lux */
+        {  800,  160.0 },  /* from  151 -  800 adc, we map to   160.0 lux */
+        {  900,  225.0 },  /* from  801 -  900 adc, we map to   225.0 lux */
+        { 1000,  320.0 },  /* from  901 - 1000 adc, we map to   320.0 lux */
+        { 1200,  640.0 },  /* from 1001 - 1200 adc, we map to   640.0 lux */
+        { 1400, 1280.0 },  /* from 1201 - 1400 adc, we map to  1280.0 lux */
+        { 1600, 2600.0 },  /* from 1401 - 1600 adc, we map to  2600.0 lux */
+        { 4095, 10240.0 }, /* from 1601 - 4095 adc, we map to 10240.0 lux */
+    };
+    size_t i;
+    for (i = 0; i < ARRAY_SIZE(adcToLux); i++) {
+        if (index < adcToLux[i].adc_value) {
+            return adcToLux[i].lux_value;
+        }
+    }
+    return adcToLux[ARRAY_SIZE(adcToLux)-1].lux_value;
 }