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

device/generic_sensor/platform_sensor_provider_iio.h

+// 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.
+
+#ifndef DEVICE_GENERIC_SENSOR_PUBLIC_PLATFORM_SENSOR_PROVIDER_IIO_H_
+#define DEVICE_GENERIC_SENSOR_PUBLIC_PLATFORM_SENSOR_PROVIDER_IIO_H_
+
+#include "device/generic_sensor/platform_sensor_provider.h"
+
+namespace base {
+class Thread;
+}
+
+namespace device {
+
+struct SensorDataIio;
+class SensorReader;
+
+class PlatformSensorProviderIio : public PlatformSensorProvider {

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

shouldn't the platform-specific implementations live in *_linux or *_chromeos
files?

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

chromeos and linux share the same code. that is why it was decided to name them
*_iio

[Reilly Grant (use Gerrit), 2016/10/31 19:33:21]

When Chrome OS and Linux share code we generally just call it Linux. *_linux.*
sources get built by default on Chrome OS.

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

Done.

+ public:
+  PlatformSensorProviderIio();
+  ~PlatformSensorProviderIio() override;
+
+  static PlatformSensorProviderIio* GetInstance();
+
+ protected:
+  void CreateSensorInternal(mojom::SensorType type,
+                            mojo::ScopedSharedBufferMapping mapping,
+                            const CreateSensorCallback& callback) override;
+
+  void AllSensorsRemoved() override;
+
+  void SetFileTaskRunner(
+      scoped_refptr<base::SingleThreadTaskRunner> file_task_runner) override;
+
+ private:
+  void SensorReaderFound(
+      mojom::SensorType type,
+      mojo::ScopedSharedBufferMapping mapping,
+      const PlatformSensorProviderBase::CreateSensorCallback& callback,
+      const SensorDataIio& data,
+      std::unique_ptr<SensorReader> sensor_reader);
+
+  // Stops a polling thread if there are no sensors left.
+  void StopPollingThread();
+
+  // TODO(maksims): make a separate class Manager that will
+  // create provide sensors with a polling task runner, 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, this thread is used to find sensors files and poll data.
+  std::unique_ptr<base::Thread> polling_thread_;

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

is this a single thread per renderer or browser? maybe having one 'singleton'
polling thread is sufficient?

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

It's a single thread per browser.

+
+  // A task runner that is passed to polling sensors to poll data.
+  scoped_refptr<base::SingleThreadTaskRunner> polling_thread_task_runner_;
+
+  // Browser's file thread task runner passed from renderer. Used to
+  // stop a polling thread.
+  scoped_refptr<base::SingleThreadTaskRunner> file_task_runner_;
+
+  DISALLOW_COPY_AND_ASSIGN(PlatformSensorProviderIio);
+};
+
+}  // namespace device
+
+#endif /* DEVICE_GENERIC_SENSOR_PUBLIC_PLATFORM_SENSOR_PROVIDER_IIO_H_ */

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

usually
#endif  // DEVICE_GENERIC...

[maksims (do not use this acc), 2016/11/01 08:14:08]

Done.