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

device/generic_sensor/platform_sensor_provider_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_provider_linux.h"
+
+#include "base/memory/singleton.h"
+#include "base/task_runner_util.h"
+#include "base/threading/thread.h"
+#include "device/generic_sensor/linux/platform_sensor_utils_linux.h"
+#include "device/generic_sensor/linux/sensor_data_linux.h"
+#include "device/generic_sensor/platform_sensor_linux.h"
+
+namespace device {
+
+// static
+PlatformSensorProviderLinux* PlatformSensorProviderLinux::GetInstance() {
+  return base::Singleton<
+      PlatformSensorProviderLinux,
+      base::LeakySingletonTraits<PlatformSensorProviderLinux>>::get();
+}
+
+PlatformSensorProviderLinux::PlatformSensorProviderLinux() = default;
+
+PlatformSensorProviderLinux::~PlatformSensorProviderLinux() = default;
+
+void PlatformSensorProviderLinux::CreateSensorInternal(
+    mojom::SensorType type,
+    mojo::ScopedSharedBufferMapping mapping,
+    const CreateSensorCallback& callback) {
+  SensorDataLinux data;
+  if (!InitSensorData(type, &data)) {
+    callback.Run(nullptr);
+    return;
+  }
+
+  if (!polling_thread_)
+    polling_thread_.reset(new base::Thread("Sensor polling thread"));
+
+  if (!polling_thread_->IsRunning()) {
+    if (!polling_thread_->StartWithOptions(
+            base::Thread::Options(base::MessageLoop::TYPE_IO, 0))) {
+      callback.Run(nullptr);
+      return;
+    }
+    polling_thread_task_runner_ = polling_thread_->task_runner();
+  }
+
+  base::PostTaskAndReplyWithResult(
+      polling_thread_task_runner_.get(), FROM_HERE,
+      base::Bind(SensorReader::Create, data),
+      base::Bind(&PlatformSensorProviderLinux::SensorReaderFound,
+                 base::Unretained(this), type, base::Passed(&mapping), callback,
+                 data));
+}
+
+void PlatformSensorProviderLinux::SensorReaderFound(
+    mojom::SensorType type,
+    mojo::ScopedSharedBufferMapping mapping,
+    const PlatformSensorProviderBase::CreateSensorCallback& callback,
+    const SensorDataLinux& data,
+    std::unique_ptr<SensorReader> sensor_reader) {
+  DCHECK(CalledOnValidThread());
+
+  if (!sensor_reader) {
+    // If there are no sensors, stop polling thread.
+    if (!HasSensors())
+      AllSensorsRemoved();
+    callback.Run(nullptr);
+    return;
+  }
+
+  callback.Run(new PlatformSensorLinux(type, std::move(mapping), this, data,
+                                       std::move(sensor_reader),
+                                       polling_thread_task_runner_));
+}
+
+void PlatformSensorProviderLinux::SetFileTaskRunner(
+    scoped_refptr<base::SingleThreadTaskRunner> file_task_runner) {
+  DCHECK(CalledOnValidThread());
+  if (!file_task_runner_)
+    file_task_runner_ = file_task_runner;
+}
+
+void PlatformSensorProviderLinux::AllSensorsRemoved() {
+  DCHECK(CalledOnValidThread());
+  DCHECK(file_task_runner_);
+  // When there are no sensors left, the polling thread must be stopped.
+  // Stop() can only be called on a different thread that allows io.
+  // Thus, browser's file thread is used for this purpose.
+  file_task_runner_->PostTask(
+      FROM_HERE, base::Bind(&PlatformSensorProviderLinux::StopPollingThread,
+                            base::Unretained(this)));
+}
+
+void PlatformSensorProviderLinux::StopPollingThread() {
+  DCHECK(file_task_runner_);
+  DCHECK(file_task_runner_->BelongsToCurrentThread());
+  polling_thread_->Stop();
+}
+
+}  // namespace device