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

device/generic_sensor/platform_sensor_iio.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_iio.h"
+
+#include "base/threading/thread.h"
+#include "base/timer/timer.h"
+#include "device/generic_sensor/iio/platform_sensor_utils_iio.h"
+#include "device/generic_sensor/iio/sensor_data_iio.h"
+
+namespace device {
+
+namespace {
+
+// Checks if at least one value has been changed.
+bool HasValuesChanged(const SensorReading& lhs, const SensorReading& rhs) {

[Reilly Grant (use Gerrit), 2016/10/24 21:49:27]

HaveValuesChanged

[maksims (do not use this acc), 2016/10/25 06:23:54]

Done.

+  return lhs.values[0] != rhs.values[0] || lhs.values[1] != rhs.values[1] ||
+         lhs.values[2] != rhs.values[2];
+}
+
+}  // namespace
+
+PlatformSensorIio::PlatformSensorIio(
+    mojom::SensorType type,
+    mojo::ScopedSharedBufferMapping mapping,
+    PlatformSensorProvider* provider,
+    const SensorDataIio& data,
+    std::unique_ptr<base::Thread> polling_thread,
+    std::unique_ptr<SensorReader> sensor_reader)
+    : 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_(std::move(polling_thread)),
+      polling_thread_task_runner_(polling_thread_->task_runner()),
+      weak_factory_(this) {}
+
+PlatformSensorIio::~PlatformSensorIio() {
+  polling_thread_task_runner_->DeleteSoon(FROM_HERE, timer_);
+}
+
+mojom::ReportingMode PlatformSensorIio::GetReportingMode() {
+  return reporting_mode_;
+}
+
+bool PlatformSensorIio::StartSensor(
+    const PlatformSensorConfiguration& configuration) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  if (!polling_thread_->IsRunning() &&
+      !polling_thread_->StartWithOptions(
+          base::Thread::Options(base::MessageLoop::TYPE_IO, 0))) {
+    return false;
+  }
+
+  return polling_thread_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&PlatformSensorIio::BeginPoll,
+                            weak_factory_.GetWeakPtr(), configuration));
+}
+
+void PlatformSensorIio::StopSensor() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  if (polling_thread_->IsRunning()) {
+    polling_thread_task_runner_->PostTask(
+        FROM_HERE, base::Bind(&PlatformSensorIio::StopPoll, this));
+  }
+}
+
+bool PlatformSensorIio::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 PlatformSensorIio::GetDefaultConfiguration() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  return default_configuration_;
+}
+
+void PlatformSensorIio::BeginPoll(
+    const PlatformSensorConfiguration& configuration) {
+  DCHECK(polling_thread_task_runner_->BelongsToCurrentThread());
+  timer_->Start(FROM_HERE, base::TimeDelta::FromMicroseconds(
+                               base::Time::kMicrosecondsPerSecond /
+                               configuration.frequency()),
+                this, &PlatformSensorIio::PollForReadingData);
+}
+
+void PlatformSensorIio::StopPoll() {
+  DCHECK(polling_thread_task_runner_->BelongsToCurrentThread());
+  timer_->Stop();
+}
+
+void PlatformSensorIio::PollForReadingData() {
+  DCHECK(polling_thread_task_runner_->BelongsToCurrentThread());
+
+  SensorReading reading;
+  if (!sensor_reader_->ReadSensorReading(&reading)) {
+    task_runner_->PostTask(
+        FROM_HERE, base::Bind(&PlatformSensorIio::NotifySensorError, this));
+    StopPoll();
+    return;
+  }
+
+  bool notifyNeeded = false;
+  if ((GetReportingMode() == mojom::ReportingMode::ON_CHANGE)) {

[Reilly Grant (use Gerrit), 2016/10/24 21:49:27]

nit: Extra set of parens.

[maksims (do not use this acc), 2016/10/25 06:23:54]

Done.

+    if (!HasValuesChanged(reading, old_values_)) {
+      return;
+    }

[Reilly Grant (use Gerrit), 2016/10/24 21:49:27]

nit: No braces around single-line if.

[maksims (do not use this acc), 2016/10/25 06:23:54]

Done.

+    notifyNeeded = true;
+  }
+
+  old_values_ = reading;
+  reading.timestamp = (base::TimeTicks::Now() - base::TimeTicks()).InSecondsF();
+  UpdateSensorReading(reading, notifyNeeded);
+}
+
+}  // namespace device