[sensors][CrOS/Linux] Implementation of motion sensors for CrOS/Linux platforms

device/generic_sensor/linux/platform_sensor_utils_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 "device/generic_sensor/linux/platform_sensor_utils_linux.h"
 
 #include "base/files/file_enumerator.h"
 #include "base/files/file_util.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_util.h"
 #include "base/threading/thread_restrictions.h"
-#include "device/generic_sensor/linux/sensor_data_linux.h"
 #include "device/generic_sensor/public/cpp/sensor_reading.h"
 
 namespace device {
 
 namespace {
 
 bool InitSensorPaths(const std::vector<std::string>& input_names,
                      const char* base_path,
                      std::vector<base::FilePath>* sensor_paths) {
   // Search the iio/devices directory for a subdirectory (eg "device0" or
@@ skipping 22 matching lines @@
   // treated as a non-existing one.
   for (auto const& file_names : data.sensor_file_names) {
     // Supply InitSensorPaths() with a set of files.
     // Only one file from each set should be found.
     if (!InitSensorPaths(file_names, data.base_path_sensor_linux, sensor_paths))
       return false;
   }
   return true;
 }
 
+// Returns -1 if unable to read a scaling value, 1 if scaling value is not
+// found. Otherwise, returns a scaling value read from a file.
+double GetSensorScalingValue(const base::FilePath& scale_file_path) {
+  if (!base::PathExists(scale_file_path))
+    return 1;
+
+  std::string value;
+  if (!base::ReadFileToString(scale_file_path, &value))
+    return -1;
+
+  double scaling_value;
+  base::TrimWhitespaceASCII(value, base::TRIM_ALL, &value);
+  if (!base::StringToDouble(value, &scaling_value))
+    return -1;
+  return scaling_value;
+}
+
 }  // namespace
 
 // static
 std::unique_ptr<SensorReader> SensorReader::Create(
     const SensorDataLinux& data) {
   base::ThreadRestrictions::AssertIOAllowed();
   std::vector<base::FilePath> sensor_paths;
   if (!GetSensorFilePaths(data, &sensor_paths))
     return nullptr;
-  return base::WrapUnique(new SensorReader(std::move(sensor_paths)));
+
+  DCHECK(!sensor_paths.empty());
+  const base::FilePath scale_file_path =
+      sensor_paths.back().DirName().Append(data.sensor_scale_name);
+  double scaling_value = GetSensorScalingValue(scale_file_path);
+
+  // A file with a scaling value is found, but couldn't be read.
+  if (scaling_value == -1)
+    return nullptr;
+
+  return base::WrapUnique(new SensorReader(
+      std::move(sensor_paths), scaling_value, data.apply_scaling_func));
 }
 
-SensorReader::SensorReader(std::vector<base::FilePath> sensor_paths)
-    : sensor_paths_(std::move(sensor_paths)) {
+SensorReader::SensorReader(
+    std::vector<base::FilePath> sensor_paths,
+    double scaling_value,
+    const SensorDataLinux::ReaderFunctor& apply_scaling_func)
+    : sensor_paths_(std::move(sensor_paths)),
+      scaling_value_(scaling_value),
+      apply_scaling_func_(apply_scaling_func) {
   DCHECK(!sensor_paths_.empty());
 }
 
 SensorReader::~SensorReader() = default;
 
 bool SensorReader::ReadSensorReading(SensorReading* reading) {
   base::ThreadRestrictions::AssertIOAllowed();
   SensorReading readings;
   DCHECK_LE(sensor_paths_.size(), arraysize(readings.values));
   int i = 0;
   for (const auto& path : sensor_paths_) {
     std::string new_read_value;
     if (!base::ReadFileToString(path, &new_read_value))
       return false;
 
     double new_value = 0;
     base::TrimWhitespaceASCII(new_read_value, base::TRIM_ALL, &new_read_value);
     if (!base::StringToDouble(new_read_value, &new_value))
       return false;
     readings.values[i++] = new_value;
   }
+  if (!apply_scaling_func_.is_null())
+    apply_scaling_func_.Run(scaling_value_, readings);
   *reading = readings;
   return true;
 }
 
 }  // namespace device