Reland of [sensors] Ambient light sensor implementation for ChromeOS and Linux.

device/generic_sensor/platform_sensor_linux.cc

Index: device/generic_sensor/platform_sensor_linux.cc
diff --git a/device/generic_sensor/platform_sensor_linux.cc b/device/generic_sensor/platform_sensor_linux.cc
new file mode 100644
index 0000000000000000000000000000000000000000..3495659729c1035f8a50687ce6fbebb4fc961615
--- /dev/null
+++ b/device/generic_sensor/platform_sensor_linux.cc
@@ -0,0 +1,114 @@
+// 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_linux.h"
+
+#include "base/threading/thread.h"
+#include "base/timer/timer.h"
+#include "device/generic_sensor/linux/platform_sensor_utils_linux.h"
+#include "device/generic_sensor/linux/sensor_data_linux.h"
+
+namespace device {
+
+namespace {
+
+// Checks if at least one value has been changed.
+bool HaveValuesChanged(const SensorReading& lhs, const SensorReading& rhs) {
+  return lhs.values[0] != rhs.values[0] || lhs.values[1] != rhs.values[1] ||
+         lhs.values[2] != rhs.values[2];
+}
+
+}  // namespace
+
+PlatformSensorLinux::PlatformSensorLinux(
+    mojom::SensorType type,
+    mojo::ScopedSharedBufferMapping mapping,
+    PlatformSensorProvider* provider,
+    const SensorDataLinux& data,
+    std::unique_ptr<SensorReader> sensor_reader,
+    scoped_refptr<base::SingleThreadTaskRunner> polling_thread_task_runner_)
+    : PlatformSensor(type, std::move(mapping), provider),
+      timer_(new base::RepeatingTimer()),
+      default_configuration_(data.default_configuration),
+      reporting_mode_(data.reporting_mode),
+      sensor_reader_(std::move(sensor_reader)),
+      polling_thread_task_runner_(polling_thread_task_runner_),
+      weak_factory_(this) {}
+
+PlatformSensorLinux::~PlatformSensorLinux() {
+  polling_thread_task_runner_->DeleteSoon(FROM_HERE, timer_);
+}
+
+mojom::ReportingMode PlatformSensorLinux::GetReportingMode() {
+  return reporting_mode_;
+}
+
+bool PlatformSensorLinux::StartSensor(
+    const PlatformSensorConfiguration& configuration) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  return polling_thread_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&PlatformSensorLinux::BeginPoll,
+                            weak_factory_.GetWeakPtr(), configuration));
+}
+
+void PlatformSensorLinux::StopSensor() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  polling_thread_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&PlatformSensorLinux::StopPoll, this));
+}
+
+bool PlatformSensorLinux::CheckSensorConfiguration(
+    const PlatformSensorConfiguration& configuration) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  // TODO(maksims): make this sensor dependent.
+  // For example, in case of accelerometer, check current polling frequency
+  // exposed by iio driver.
+  return configuration.frequency() > 0 &&
+         configuration.frequency() <=
+             mojom::SensorConfiguration::kMaxAllowedFrequency;
+}
+
+PlatformSensorConfiguration PlatformSensorLinux::GetDefaultConfiguration() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  return default_configuration_;
+}
+
+void PlatformSensorLinux::BeginPoll(
+    const PlatformSensorConfiguration& configuration) {
+  DCHECK(polling_thread_task_runner_->BelongsToCurrentThread());
+  timer_->Start(FROM_HERE, base::TimeDelta::FromMicroseconds(
+                               base::Time::kMicrosecondsPerSecond /
+                               configuration.frequency()),
+                this, &PlatformSensorLinux::PollForReadingData);
+}
+
+void PlatformSensorLinux::StopPoll() {
+  DCHECK(polling_thread_task_runner_->BelongsToCurrentThread());
+  timer_->Stop();
+}
+
+void PlatformSensorLinux::PollForReadingData() {
+  DCHECK(polling_thread_task_runner_->BelongsToCurrentThread());
+
+  SensorReading reading;
+  if (!sensor_reader_->ReadSensorReading(&reading)) {
+    task_runner_->PostTask(
+        FROM_HERE, base::Bind(&PlatformSensorLinux::NotifySensorError, this));
+    StopPoll();
+    return;
+  }
+
+  bool notifyNeeded = false;
+  if (GetReportingMode() == mojom::ReportingMode::ON_CHANGE) {
+    if (!HaveValuesChanged(reading, old_values_))
+      return;
+    notifyNeeded = true;
+  }
+
+  old_values_ = reading;
+  reading.timestamp = (base::TimeTicks::Now() - base::TimeTicks()).InSecondsF();
+  UpdateSensorReading(reading, notifyNeeded);
+}
+
+}  // namespace device