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

device/generic_sensor/linux/sensor_data_linux.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "base/sys_info.h"
 #include "base/version.h"
 #include "device/generic_sensor/generic_sensor_consts.h"
 #include "device/generic_sensor/linux/sensor_data_linux.h"
 #include "device/generic_sensor/public/cpp/sensor_reading.h"
 
@@ skipping 56 matching lines @@
   std::vector<std::string> file_names_y{"in_accel_y_base_raw",
                                         "in_accel_y_raw"};
   std::vector<std::string> file_names_z{"in_accel_z_base_raw",
                                         "in_accel_z_raw"};
 
 #if defined(OS_CHROMEOS)
   data->sensor_scale_name = "in_accel_base_scale";
   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";
   data->sensor_offset_file_name = "in_accel_offset";
   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
 
   MaybeCheckKernelVersionAndAssignFileNames(file_names_x, file_names_y,
                                             file_names_z, data);
   data->default_configuration =
       PlatformSensorConfiguration(kDefaultAccelerometerFrequencyHz);
 }
 
 void InitGyroscopeSensorData(SensorPathsLinux* data) {
   std::vector<std::string> file_names_x{"in_anglvel_x_base_raw",
                                         "in_anglvel_x_raw"};
   std::vector<std::string> file_names_y{"in_anglvel_y_base_raw",
                                         "in_anglvel_y_raw"};
   std::vector<std::string> file_names_z{"in_anglvel_z_base_raw",
                                         "in_anglvel_z_raw"};
 #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
 
   MaybeCheckKernelVersionAndAssignFileNames(file_names_x, file_names_y,
                                             file_names_z, data);
   data->default_configuration =
       PlatformSensorConfiguration(kDefaultGyroscopeFrequencyHz);
 }
 
 // TODO(maksims): Verify magnitometer works correctly on a chromebook when
 // I get one with that sensor onboard.
 void InitMagnitometerSensorData(SensorPathsLinux* data) {
   std::vector<std::string> file_names_x{"in_magn_x_raw"};
   std::vector<std::string> file_names_y{"in_magn_y_raw"};
   std::vector<std::string> file_names_z{"in_magn_z_raw"};
 
   data->sensor_scale_name = "in_magn_scale";
   data->sensor_offset_file_name = "in_magn_offset";
   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,
                                             file_names_z, data);
   data->default_configuration =
       PlatformSensorConfiguration(kDefaultMagnetometerFrequencyHz);
 }
 
 }  // namespace
 
@@ skipping 40 matching lines @@
       device_frequency(sensor_device_frequency),
       device_scaling_value(sensor_device_scaling_value),
       device_offset_value(sensor_device_offset_value),
       reporting_mode(mode),
       apply_scaling_func(scaling_func),
       device_reading_files(std::move(device_reading_files)) {}
 
 SensorInfoLinux::~SensorInfoLinux() = default;
 
 }  // namespace device