[sensors](CrOS/Linux) Implement Sensor device manager for sensors

device/generic_sensor/platform_sensor_manager_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/platform_sensor_manager_linux.h"
+
+#include "base/strings/string_number_conversions.h"
+#include "base/threading/thread_restrictions.h"
+#include "base/threading/thread_task_runner_handle.h"
+#include "device/generic_sensor/linux/sensor_data_linux.h"
+
+namespace device {
+
+namespace {
+
+std::string StringOrEmptyIfNull(const char* value) {
+  return value ? value : std::string();
+}
+
+}  // namespace
+
+SensorDeviceManager::SensorDeviceManager()
+    : observer_(this),
+      delegate_(nullptr),
+      task_runner_(base::ThreadTaskRunnerHandle::Get()) {
+  thread_checker_.DetachFromThread();
+}
+
+SensorDeviceManager::~SensorDeviceManager() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+}
+
+void SensorDeviceManager::Start(Delegate* delegate) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  base::ThreadRestrictions::AssertIOAllowed();
+
+  delegate_ = delegate;

[Reilly Grant (use Gerrit), 2016/12/08 02:31:15]

DCHECK(!delegate_)?

[maksims (do not use this acc), 2016/12/08 18:39:17]

Well, yeah. Good point.

+
+  DeviceMonitorLinux* monitor = DeviceMonitorLinux::GetInstance();
+  observer_.Add(monitor);
+  monitor->Enumerate(
+      base::Bind(&SensorDeviceManager::OnDeviceAdded, base::Unretained(this)));
+
+  task_runner_->PostTask(
+      FROM_HERE, base::Bind(&SensorDeviceManager::Delegate::OnEnumerationReady,
+                            base::Unretained(delegate_)));
+}
+
+std::string SensorDeviceManager::GetUdevDeviceGetSubsystem(udev_device* dev) {
+  return StringOrEmptyIfNull(udev_device_get_subsystem(dev));
+}
+
+std::string SensorDeviceManager::GetUdevDeviceGetSyspath(udev_device* dev) {
+  return StringOrEmptyIfNull(udev_device_get_syspath(dev));
+}
+
+std::string SensorDeviceManager::GetUdevDeviceGetSysattrValue(
+    udev_device* dev,
+    const std::string& attribute) {
+  return StringOrEmptyIfNull(
+      udev_device_get_sysattr_value(dev, attribute.c_str()));
+}
+
+std::string SensorDeviceManager::GetUdevDeviceGetDevnode(udev_device* dev) {
+  return StringOrEmptyIfNull(udev_device_get_devnode(dev));
+}
+
+void SensorDeviceManager::OnDeviceAdded(udev_device* dev) {
+  const std::string subsystem = GetUdevDeviceGetSubsystem(dev);
+  if (subsystem.empty() || subsystem.compare("iio") != 0)
+    return;
+
+  const std::string sysfs_path = GetUdevDeviceGetSyspath(dev);
+  if (sysfs_path.empty())
+    return;
+
+  const std::string device_node = GetUdevDeviceGetDevnode(dev);
+  if (device_node.empty())
+    return;
+
+  const uint32_t first = static_cast<uint32_t>(mojom::SensorType::FIRST);
+  const uint32_t last = static_cast<uint32_t>(mojom::SensorType::LAST);
+  for (uint32_t i = first; i < last; ++i) {
+    SensorPathsLinux data;
+    mojom::SensorType type = static_cast<mojom::SensorType>(i);
+    if (!InitSensorData(type, &data)) {
+      continue;
+    }

[Reilly Grant (use Gerrit), 2016/12/08 02:31:14]

nit: no braces around single-line if

[maksims (do not use this acc), 2016/12/08 18:39:17]

Done.

+
+    std::vector<base::FilePath> sensor_file_names;
+    for (auto const& names : data.sensor_file_names) {

[Reilly Grant (use Gerrit), 2016/12/08 02:31:14]

Spell out the type here so that it is clear what type |name| has below. The
nesting makes it otherwise confusing.

[maksims (do not use this acc), 2016/12/08 18:39:17]

Done.

+      for (auto const& name : names) {

[Reilly Grant (use Gerrit), 2016/12/08 02:31:14]

const auto&

[maksims (do not use this acc), 2016/12/08 18:39:17]

Done.

+        const std::string value =
+            GetUdevDeviceGetSysattrValue(dev, name.c_str());
+        if (value.empty())
+          continue;
+        base::FilePath full_path = base::FilePath(sysfs_path).Append(name);
+        sensor_file_names.push_back(full_path);
+        break;
+      }
+    }
+
+    if (sensor_file_names.empty())
+      continue;
+
+    const std::string scaling_value =
+        GetUdevDeviceGetSysattrValue(dev, data.sensor_scale_name.c_str());
+    // If scaling value is not found, treat it as 1.
+    double sensor_scaling_value = 1;
+    if (!scaling_value.empty())
+      base::StringToDouble(scaling_value, &sensor_scaling_value);
+
+    const std::string offset_vallue =
+        GetUdevDeviceGetSysattrValue(dev, data.sensor_offset_file_name.c_str());
+    // If offset value is not found, treat it as 0.
+    double sensor_offset_value = 0;
+    if (!offset_vallue.empty())
+      base::StringToDouble(offset_vallue, &sensor_offset_value);
+
+    const std::string frequency_value = GetUdevDeviceGetSysattrValue(
+        dev, data.sensor_frequency_file_name.c_str());
+    // If frequency is not found, use default one from SensorPathsLinux struct.
+    double sensor_frequency_value = data.default_configuration.frequency();
+    // By default, |reporting_mode| is ON_CHANGE. But if platform provides
+    // sampling frequency, the reporting mode is CONTINUOUS.
+    mojom::ReportingMode reporting_mode = mojom::ReportingMode::ON_CHANGE;
+    if (!frequency_value.empty()) {
+      base::StringToDouble(frequency_value, &sensor_frequency_value);
+      reporting_mode = mojom::ReportingMode::CONTINUOUS;
+    }
+
+    // Update own cache of known sensor devices.
+    if (!base::ContainsKey(sensors_by_node_, device_node))
+      sensors_by_node_[device_node] = data.type;
+
+    std::unique_ptr<SensorInfoLinux> device(new SensorInfoLinux(
+        device_node, sensor_frequency_value, sensor_scaling_value,
+        sensor_offset_value, reporting_mode, data.apply_scaling_func,
+        std::move(sensor_file_names)));
+    task_runner_->PostTask(
+        FROM_HERE, base::Bind(&SensorDeviceManager::Delegate::OnDeviceAdded,
+                              base::Unretained(delegate_), data.type,
+                              base::Passed(&device)));
+
+    // One |dev| can represent more than one sensor.
+    // For example, there is an accelerometer and gyroscope represented by one
+    // |dev| in Chrome OS, kernel < 3.18. Thus, iterate through all possible
+    // types of sensors.
+  }
+}
+
+void SensorDeviceManager::OnDeviceRemoved(udev_device* dev) {
+  const std::string subsystem = GetUdevDeviceGetSubsystem(dev);
+  if (subsystem.empty() || subsystem.compare("iio") != 0)
+    return;
+
+  const std::string device_node = GetUdevDeviceGetDevnode(dev);
+  if (device_node.empty())
+    return;
+
+  auto sensor = sensors_by_node_.find(device_node);
+  if (sensor == sensors_by_node_.end())
+    return;
+  mojom::SensorType type = sensor->second;
+  sensors_by_node_.erase(sensor);
+
+  task_runner_->PostTask(
+      FROM_HERE, base::Bind(&SensorDeviceManager::Delegate::OnDeviceRemoved,
+                            base::Unretained(delegate_), type, device_node));
+}
+
+}  // namespace device