[sensors](CrOS/Linux) Fix calculations with offset

This cl fixes calculations done with offset value.
Offset value must be added to a raw value and only then multiplied
by a scaling value.
The formula is the following:
processed value = (raw + offset) * scale

BUG=661478

Review-Url: https://codereview.chromium.org/2570693004
Cr-Commit-Position: refs/heads/master@{#438132}

device/generic_sensor/linux/sensor_data_linux.cc

@@ -74,10 +74,10 @@ void InitAccelerometerSensorData(SensorPathsLinux* data) {
   data->sensor_frequency_file_name = "in_accel_base_sampling_frequency";
   data->apply_scaling_func = base::Bind(
       [](double scaling_value, double offset, SensorReading& reading) {
-        double scaling = (kMeanGravity / scaling_value) + offset;
-        reading.values[0] = scaling * reading.values[0];
-        reading.values[1] = scaling * reading.values[1];
-        reading.values[2] = scaling * reading.values[2];
+        double scaling = kMeanGravity / scaling_value;
+        reading.values[0] = scaling * (reading.values[0] + offset);
+        reading.values[1] = scaling * (reading.values[1] + offset);
+        reading.values[2] = scaling * (reading.values[2] + offset);
       });
 #else
   data->sensor_scale_name = "in_accel_scale";
@@ -85,11 +85,10 @@ void InitAccelerometerSensorData(SensorPathsLinux* data) {
   data->sensor_frequency_file_name = "in_accel_sampling_frequency";
   data->apply_scaling_func = base::Bind(
       [](double scaling_value, double offset, SensorReading& reading) {
-        double scaling = scaling_value + offset;
         // Adapt Linux reading values to generic sensor api specs.
-        reading.values[0] = -scaling * reading.values[0];
-        reading.values[1] = -scaling * reading.values[1];
-        reading.values[2] = -scaling * reading.values[2];
+        reading.values[0] = -scaling_value * (reading.values[0] + offset);
+        reading.values[1] = -scaling_value * (reading.values[1] + offset);
+        reading.values[2] = -scaling_value * (reading.values[2] + offset);
       });
 #endif
 
@@ -109,25 +108,23 @@ void InitGyroscopeSensorData(SensorPathsLinux* data) {
 #if defined(OS_CHROMEOS)
   data->sensor_scale_name = "in_anglvel_base_scale";
   data->sensor_frequency_file_name = "in_anglvel_base_frequency";
-  data->apply_scaling_func = base::Bind(
-      [](double scaling_value, double offset, SensorReading& reading) {
-        double scaling =
-            kMeanGravity * kRadiansInDegreesPerSecond / scaling_value + offset;
-        // Adapt CrOS reading values to generic sensor api specs.
-        reading.values[0] = -scaling * reading.values[0];
-        reading.values[1] = -scaling * reading.values[1];
-        reading.values[2] = -scaling * reading.values[2];
-      });
+  data->apply_scaling_func = base::Bind([](double scaling_value, double offset,
+                                           SensorReading& reading) {
+    double scaling = kMeanGravity * kRadiansInDegreesPerSecond / scaling_value;
+    // Adapt CrOS reading values to generic sensor api specs.
+    reading.values[0] = -scaling * (reading.values[0] + offset);
+    reading.values[1] = -scaling * (reading.values[1] + offset);
+    reading.values[2] = -scaling * (reading.values[2] + offset);
+  });
 #else
   data->sensor_scale_name = "in_anglvel_scale";
   data->sensor_offset_file_name = "in_anglvel_offset";
   data->sensor_frequency_file_name = "in_anglvel_sampling_frequency";
   data->apply_scaling_func = base::Bind(
       [](double scaling_value, double offset, SensorReading& reading) {
-        double scaling = scaling_value + offset;
-        reading.values[0] = scaling * reading.values[0];
-        reading.values[1] = scaling * reading.values[1];
-        reading.values[2] = scaling * reading.values[2];
+        reading.values[0] = scaling_value * (reading.values[0] + offset);
+        reading.values[1] = scaling_value * (reading.values[1] + offset);
+        reading.values[2] = scaling_value * (reading.values[2] + offset);
       });
 #endif
 
@@ -149,10 +146,10 @@ void InitMagnitometerSensorData(SensorPathsLinux* data) {
   data->sensor_frequency_file_name = "in_magn_sampling_frequency";
   data->apply_scaling_func = base::Bind(
       [](double scaling_value, double offset, SensorReading& reading) {
-        double scaling = scaling_value + offset;
-        reading.values[0] = scaling * kMicroteslaInGauss * reading.values[0];
-        reading.values[1] = scaling * kMicroteslaInGauss * reading.values[1];
-        reading.values[2] = scaling * kMicroteslaInGauss * reading.values[2];
+        double scaling = scaling_value * kMicroteslaInGauss;
+        reading.values[0] = scaling * (reading.values[0] + offset);
+        reading.values[1] = scaling * (reading.values[1] + offset);
+        reading.values[2] = scaling * (reading.values[2] + offset);
       });
 
   MaybeCheckKernelVersionAndAssignFileNames(file_names_x, file_names_y,

device/generic_sensor/platform_sensor_and_provider_unittest_linux.cc

@@ -550,10 +550,13 @@ TEST_F(PlatformSensorAndProviderLinuxTest,
   EXPECT_THAT(buffer->reading.values[1], scaling * sensor_values[1]);
   EXPECT_THAT(buffer->reading.values[2], scaling * sensor_values[2]);
 #else
-  double scaling = kAccelerometerScalingValue + kAccelerometerOffsetValue;
-  EXPECT_THAT(buffer->reading.values[0], -scaling * sensor_values[0]);
-  EXPECT_THAT(buffer->reading.values[1], -scaling * sensor_values[1]);
-  EXPECT_THAT(buffer->reading.values[2], -scaling * sensor_values[2]);
+  double scaling = kAccelerometerScalingValue;
+  EXPECT_THAT(buffer->reading.values[0],
+              -scaling * (sensor_values[0] + kAccelerometerOffsetValue));
+  EXPECT_THAT(buffer->reading.values[1],
+              -scaling * (sensor_values[1] + kAccelerometerOffsetValue));
+  EXPECT_THAT(buffer->reading.values[2],
+              -scaling * (sensor_values[2] + kAccelerometerOffsetValue));
 #endif
 }
 
@@ -604,10 +607,13 @@ TEST_F(PlatformSensorAndProviderLinuxTest, CheckGyroscopeReadingConversion) {
   EXPECT_THAT(buffer->reading.values[1], -scaling * sensor_values[1]);
   EXPECT_THAT(buffer->reading.values[2], -scaling * sensor_values[2]);
 #else
-  double scaling = kGyroscopeScalingValue + kGyroscopeOffsetValue;
-  EXPECT_THAT(buffer->reading.values[0], scaling * sensor_values[0]);
-  EXPECT_THAT(buffer->reading.values[1], scaling * sensor_values[1]);
-  EXPECT_THAT(buffer->reading.values[2], scaling * sensor_values[2]);
+  double scaling = kGyroscopeScalingValue;
+  EXPECT_THAT(buffer->reading.values[0],
+              scaling * (sensor_values[0] + kGyroscopeOffsetValue));
+  EXPECT_THAT(buffer->reading.values[1],
+              scaling * (sensor_values[1] + kGyroscopeOffsetValue));
+  EXPECT_THAT(buffer->reading.values[2],
+              scaling * (sensor_values[2] + kGyroscopeOffsetValue));
 #endif
 }
 
@@ -651,11 +657,13 @@ TEST_F(PlatformSensorAndProviderLinuxTest, CheckMagnetometerReadingConversion) {
 
   SensorReadingSharedBuffer* buffer =
       static_cast<SensorReadingSharedBuffer*>(mapping.get());
-  double scaling = (kMagnetometerScalingValue + kMagnetometerOffsetValue) *
-                   kMicroteslaInGauss;
-  EXPECT_THAT(buffer->reading.values[0], scaling * sensor_values[0]);
-  EXPECT_THAT(buffer->reading.values[1], scaling * sensor_values[1]);
-  EXPECT_THAT(buffer->reading.values[2], scaling * sensor_values[2]);
+  double scaling = kMagnetometerScalingValue * kMicroteslaInGauss;
+  EXPECT_THAT(buffer->reading.values[0],
+              scaling * (sensor_values[0] + kMagnetometerOffsetValue));
+  EXPECT_THAT(buffer->reading.values[1],
+              scaling * (sensor_values[1] + kMagnetometerOffsetValue));
+  EXPECT_THAT(buffer->reading.values[2],
+              scaling * (sensor_values[2] + kMagnetometerOffsetValue));
 }
 
 }  // namespace device