[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.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 base {
+class SingleThreadTaskRunner;
+}
+
+namespace device {
+
+class PlatformSensorProviderIio : public PlatformSensorProvider {
+ public:
+  PlatformSensorProviderIio();
+  ~PlatformSensorProviderIio() override;
+
+  static PlatformSensorProviderIio* GetInstance();
+
+ protected:
+  void CreateSensorInternal(mojom::SensorType type,
+                            mojo::ScopedSharedBufferMapping mapping,
+                            const CreateSensorCallback& callback) override;
+
+ private:
+  void SensorReaderFound(
+      mojom::SensorType type,
+      mojo::ScopedSharedBufferMapping mapping,
+      const PlatformSensorProviderBase::CreateSensorCallback& callback,
+      const SensorDataIio& data,
+      std::unique_ptr<base::Thread> polling_thread,
+      std::unique_ptr<SensorReader> sensor_reader);
+
+  // Helper function that gets a new sensor reader with a sensor type specific
+  // options taken from SensorDataIio.
+  std::unique_ptr<SensorReader> GetSensorReader(
+      const SensorDataIio& data,
+      scoped_refptr<base::SingleThreadTaskRunner> task_runner);
+
+  // TODO(maksims): make this as a separate class Manager that will
+  // create threads for new sensors, check sensors existence and notify provider
+  // if a new sensor has appeared and it can be created if a request comes
+  // again for the same sensor.
+  // A use case example: a request for a sensor X comes, manager checks if the
+  // sensor exists on a platform and notifies a provider it is not found.
+  // The provider stores this information into its cache and doesn't try to
+  // create this specific sensor if a request comes. But when, for example,
+  // the sensor X is plugged into a usb port, the manager notices that and
+  // notifies the provider, which updates its cache and starts handling requests
+  // for the sensor X.
+  //
+  // Right now, it is only used to delete polling threads if a new sensor
+  // is not created and the thread cannot be passed to it.
+  std::unique_ptr<base::Thread> manager_thread_;
+
+  DISALLOW_COPY_AND_ASSIGN(PlatformSensorProviderIio);
+};
+
+PlatformSensorProvider* PlatformSensorProvider::GetInstance() {
+  return PlatformSensorProviderIio::GetInstance();
+}
+
+// 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 (!CreateSensorData(type, &data)) {
+    callback.Run(nullptr);
+    return;
+  }
+
+  if (!manager_thread_) {
+    manager_thread_.reset(new base::Thread("Linux/CrOS manager thread"));
+    if (!manager_thread_->StartWithOptions(
+            base::Thread::Options(base::MessageLoop::TYPE_IO, 0))) {
+      callback.Run(nullptr);
+      return;
+    }
+  }
+
+  std::unique_ptr<base::Thread> polling_thread(
+      new base::Thread("Linux/CrOS polling sensor thread."));
+
+  if (!polling_thread->StartWithOptions(
+          base::Thread::Options(base::MessageLoop::TYPE_IO, 0))) {
+    callback.Run(nullptr);
+    return;
+  }
+
+  base::PostTaskAndReplyWithResult(
+      polling_thread->task_runner().get(), FROM_HERE,
+      base::Bind(&PlatformSensorProviderIio::GetSensorReader,
+                 base::Unretained(this), data, polling_thread->task_runner()),
+      base::Bind(&PlatformSensorProviderIio::SensorReaderFound,
+                 base::Unretained(this), type, base::Passed(&mapping), callback,
+                 data, base::Passed(&polling_thread)));
+}
+
+void PlatformSensorProviderIio::SensorReaderFound(
+    mojom::SensorType type,
+    mojo::ScopedSharedBufferMapping mapping,
+    const PlatformSensorProviderBase::CreateSensorCallback& callback,
+    const SensorDataIio& data,
+    std::unique_ptr<base::Thread> polling_thread,
+    std::unique_ptr<SensorReader> sensor_reader) {
+  DCHECK(CalledOnValidThread());
+
+  if (!sensor_reader) {
+    manager_thread_->task_runner()->DeleteSoon(FROM_HERE,
+                                               polling_thread.release());
+    callback.Run(nullptr);
+    return;
+  }
+
+  callback.Run(new PlatformSensorIio(type, std::move(mapping), this, data,
+                                     std::move(polling_thread),
+                                     std::move(sensor_reader)));
+}
+
+std::unique_ptr<SensorReader> PlatformSensorProviderIio::GetSensorReader(

[Mikhail, 2016/10/14 13:59:05]

can we do without this method? (call SensorReader::Create(data); right away)

[maksims (do not use this acc), 2016/10/17 06:06:59]

Done.

+    const SensorDataIio& data,
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner) {
+  DCHECK(task_runner->BelongsToCurrentThread());
+  return SensorReader::Create(data);
+}
+
+}  // namespace device