sensors: Return a calculated lux value instead using the current 8 entry table

The light sensor now uses the lux to current formula in the datasheet,
I = 10 * log(Ev) uA, and multiplies the result by 4 as an attempt
to correct for the glass in front of the sensor.

Also update the config_autoBrightnessLevels table so the auto brightness
change occurs at the same adc values as before (or close for 7.2 lux).

Change-Id: I121ce0f23dca093c9607ac9447b9263f48507a09

3 files changed, 8 insertions, 40 deletions

diff --git a/libsensors/LightSensor.cpp b/libsensors/LightSensor.cpp
index 15ae4e2..29b222b 100644
--- a/libsensors/LightSensor.cpp
+++ b/libsensors/LightSensor.cpp
@@ -31,46 +31,17 @@ LightSensor::LightSensor()
 {
     mPendingEvent.sensor = ID_L;
     mPendingEvent.type = SENSOR_TYPE_LIGHT;
-    mPreviousLight = -1;
-}
-
-int LightSensor::handleEnable(int en) {
-    mPreviousLight = -1;
-    return 0;
 }
 
 bool LightSensor::handleEvent(input_event const *event) {
     if (event->value == -1) {
         return false;
     }
-    mPendingEvent.light = indexToValue(event->value);
-    if (mPendingEvent.light != mPreviousLight) {
-        mPreviousLight = mPendingEvent.light;
-        return true;
-    }
-    return false;
-}
-
-float LightSensor::indexToValue(size_t index) const {
-    /* Driver gives a rolling average adc value.  We convert it lux levels. */
-    static const struct adcToLux {
-        size_t adc_value;
-        float  lux_value;
-    } adcToLux[] = {
-        {   50,   10.0 },  /* from    0 -   50 adc, we map to    10.0 lux  */
-        {  280,  160.0 },  /* from   51 -  280 adc, we map to   160.0 lux  */
-        {  320,  225.0 },  /* from  281 -  320 adc, we map to   225.0 lux  */
-        {  350,  320.0 },  /* from  321 -  350 adc, we map to   320.0 lux  */
-        {  400,  640.0 },  /* from  351 -  400 adc, we map to   640.0 lux  */
-        {  520, 1280.0 },  /* from  401 -  520 adc, we map to  1280.0 lux  */
-        {  590, 2600.0 },  /* from  521 -  590 adc, we map to  2600.0 lux  */
-        { 1024, 10240.0 }, /* from  591 - 1024 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;
+    // Convert adc value to lux assuming:
+    // I = 10 * log(Ev) uA
+    // R = 24kOhm
+    // Max adc value 1023 = 1.25V
+    // 1/4 of light reaches sensor
+    mPendingEvent.light = powf(10, event->value * (125.0f / 1023.0f / 24.0f)) * 4;
+    return true;
 }
diff --git a/libsensors/LightSensor.h b/libsensors/LightSensor.h
index ed3b435..f5f8af0 100644
--- a/libsensors/LightSensor.h
+++ b/libsensors/LightSensor.h
@@ -32,10 +32,7 @@ struct input_event;
 
 class LightSensor:public SamsungSensorBase {
 
-    float mPreviousLight;
-    virtual int handleEnable(int en);
     virtual bool handleEvent(input_event const * event);
-    float indexToValue(size_t index) const;
 public:
     LightSensor();
 };
diff --git a/libsensors/sensors.cpp b/libsensors/sensors.cpp
index 450dbd5..a884ce7 100644
--- a/libsensors/sensors.cpp
+++ b/libsensors/sensors.cpp
@@ -80,7 +80,7 @@ static struct sensor_t sSensorList[LOCAL_SENSORS + MPLSensor::numSensors] = {
       { "GP2A Light sensor",
           "Sharp",
           1, SENSORS_LIGHT_HANDLE,
-          SENSOR_TYPE_LIGHT, 3000.0f, 1.0f, 0.75f, 0, { } },
+          SENSOR_TYPE_LIGHT, powf(10, 125.0f/ 24.0f) * 4, 1.0f, 0.75f, 0, { } },
       { "GP2A Proximity sensor",
           "Sharp",
           1, SENSORS_PROXIMITY_HANDLE,