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

device/generic_sensor/platform_sensor_provider_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_provider_iio.h"
+
+#include "base/memory/singleton.h"
+#include "base/task_runner_util.h"
+#include "base/threading/thread.h"
+#include "device/generic_sensor/iio/platform_sensor_utils_iio.h"
+#include "device/generic_sensor/iio/sensor_data_iio.h"
+#include "device/generic_sensor/platform_sensor_iio.h"
+
+namespace device {
+
+// static
+PlatformSensorProviderIio* PlatformSensorProviderIio::GetInstance() {
+  return base::Singleton<
+      PlatformSensorProviderIio,
+      base::LeakySingletonTraits<PlatformSensorProviderIio>>::get();
+}
+
+PlatformSensorProviderIio::PlatformSensorProviderIio() = default;
+
+PlatformSensorProviderIio::~PlatformSensorProviderIio() = default;
+
+void PlatformSensorProviderIio::CreateSensorInternal(
+    mojom::SensorType type,
+    mojo::ScopedSharedBufferMapping mapping,
+    const CreateSensorCallback& callback) {
+  SensorDataIio data;
+  if (!InitSensorData(type, &data)) {
+    callback.Run(nullptr);
+    return;
+  }
+
+  if (!polling_thread_)
+    polling_thread_.reset(new base::Thread("Linux/CrOS manager thread"));

[timvolodine, 2016/10/31 18:28:17]

If the file is chrome/linux specific it seems to be clear this is a Linux/CrOS
thread. Maybe better name something like "Sensor polling thread" or so..

[maksims (do not use this acc), 2016/10/31 19:21:48]

thanks. forgot to change that.

+
+  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(&PlatformSensorProviderIio::SensorReaderFound,
+                 base::Unretained(this), type, base::Passed(&mapping), callback,
+                 data));
+}
+
+void PlatformSensorProviderIio::SensorReaderFound(
+    mojom::SensorType type,
+    mojo::ScopedSharedBufferMapping mapping,
+    const PlatformSensorProviderBase::CreateSensorCallback& callback,
+    const SensorDataIio& 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 PlatformSensorIio(type, std::move(mapping), this, data,
+                                     std::move(sensor_reader),
+                                     polling_thread_task_runner_));
+}
+
+void PlatformSensorProviderIio::SetFileTaskRunner(
+    scoped_refptr<base::SingleThreadTaskRunner> file_task_runner) {
+  // This task runner mustn't belong to current IO thread.
+  DCHECK(!file_task_runner->BelongsToCurrentThread());

[Mikhail, 2016/10/31 12:50:32]

think this DCHECK is unnecessary.

[maksims (do not use this acc), 2016/11/01 08:10:31]

Done.

+  file_task_runner_ = file_task_runner;

[Mikhail, 2016/10/31 12:50:32]

Should be only set once. And on the valid thread.

[maksims (do not use this acc), 2016/11/01 08:10:31]

Done.

+}
+
+void PlatformSensorProviderIio::AllSensorsRemoved() {
+  DCHECK(CalledOnValidThread());
+  file_task_runner_->PostTask(

[Mikhail, 2016/10/31 12:50:32]

pls add a short comment explaining why this delegated to file_task_runner_

[Mikhail, 2016/10/31 12:50:32]

DCHECK(file_task_runner_);

[maksims (do not use this acc), 2016/11/01 08:10:31]

Done.

[maksims (do not use this acc), 2016/11/01 08:10:31]

Done.

+      FROM_HERE, base::Bind(&PlatformSensorProviderIio::StopPollingThread,
+                            base::Unretained(this)));
+}
+
+void PlatformSensorProviderIio::StopPollingThread() {
+  DCHECK(file_task_runner_->BelongsToCurrentThread());

[Mikhail, 2016/10/31 12:50:32]

DCHECK(file_task_runner_);

[maksims (do not use this acc), 2016/11/01 08:10:31]

Done.

+  polling_thread_->Stop();
+}
+
+}  // namespace device