[sensors] [mac] Implement ambient light sensor for macOS

device/generic_sensor/platform_sensor_ambient_light_mac.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_ambient_light_mac.h"
+
+#include <IOKit/IOMessage.h>
+
+#include "base/bind.h"
+#include "device/base/synchronization/shared_memory_seqlock_buffer.h"
+#include "device/generic_sensor/platform_sensor_provider_mac.h"
+#include "device/sensors/public/cpp/device_sensors_consts.h"
+#include "device/sensors/public/cpp/device_util_mac.h"
+
+namespace device {
+
+enum LmuFunctionIndex {
+  kGetSensorReadingID = 0,  // getSensorReading(int *, int *)
+};
+
+PlatformSensorAmbientLightMac::PlatformSensorAmbientLightMac(
+    mojom::SensorType type,
+    mojo::ScopedSharedBufferMapping mapping,
+    PlatformSensorProvider* provider,
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner)
+    : PlatformSensor(type, std::move(mapping), provider),
+      light_sensor_port_(nullptr),
+      task_runner_(std::move(task_runner)),
+      current_lux_(0) {

[Mikhail, 2016/10/06 19:52:54]

nit: 0.0

+  DCHECK_EQ(type, mojom::SensorType::AMBIENT_LIGHT);
+}
+
+PlatformSensorAmbientLightMac::~PlatformSensorAmbientLightMac() = default;
+
+mojom::ReportingMode PlatformSensorAmbientLightMac::GetReportingMode() {
+  return mojom::ReportingMode::ON_CHANGE;
+}
+
+bool PlatformSensorAmbientLightMac::CheckSensorConfiguration(
+    const PlatformSensorConfiguration& configuration) {
+  return configuration.frequency() > 0 &&
+         configuration.frequency() <=
+             mojom::SensorConfiguration::kMaxAllowedFrequency;
+}
+
+PlatformSensorConfiguration
+PlatformSensorAmbientLightMac::GetDefaultConfiguration() {
+  PlatformSensorConfiguration default_configuration;
+  default_configuration.set_frequency(kDefaultAmbientLightFrequencyHz);
+  return default_configuration;
+}
+
+void PlatformSensorAmbientLightMac::IOServiceCallback(void* context,
+                                                      io_service_t service,
+                                                      natural_t message_type,
+                                                      void* message_argument) {
+  PlatformSensorAmbientLightMac* sensor =
+      static_cast<PlatformSensorAmbientLightMac*>(context);
+  uint32_t scalar_output_count = 2;
+  uint64_t lux_values[2];
+  kern_return_t kr = IOConnectCallMethod(
+      sensor->light_sensor_object_, LmuFunctionIndex::kGetSensorReadingID,
+      nullptr, 0, nullptr, 0, lux_values, &scalar_output_count, nullptr, 0);
+
+  if (kr == KERN_SUCCESS)
+    sensor->UpdateReading(lux_values);
+}
+
+bool PlatformSensorAmbientLightMac::StartSensor(
+    const PlatformSensorConfiguration& configuration) {
+  // Tested and verified by riju that the following call works on
+  // MacBookPro9,1 : Macbook Pro 15" (Mid 2012 model)
+  // MacBookPro10,1 : Macbook Pro 15" (Retina Display, Early 2013 model).
+  // MacBookPro10,2 : Macbook Pro 13" (Retina Display, Early 2013 model).
+  // MacBookAir5,2 : Macbook Air 13" (Mid 2012 model) (by François Beaufort).
+  // MacBookAir6,2 : Macbook Air 13" (Mid 2013 model).
+  // Testing plans : please download the code and follow the comments :-
+  // https://gist.github.com/riju/74af8c81a665e412d122/
+  // and add an entry here about the model and the status returned by the code.
+
+  // Look up a registered IOService object whose class is AppleLMUController.
+  light_sensor_service_.reset(IOServiceGetMatchingService(
+      kIOMasterPortDefault, IOServiceMatching("AppleLMUController")));
+
+  // Return early if the ambient light sensor is not present.
+  if (!light_sensor_service_)
+    return false;
+
+  light_sensor_port_.reset(IONotificationPortCreate(kIOMasterPortDefault));
+  if (!light_sensor_port_.is_valid())
+    return false;
+
+  IONotificationPortSetDispatchQueue(
+      light_sensor_port_.get(),
+      dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_BACKGROUND, 0));
+
+  kern_return_t kr = IOServiceAddInterestNotification(
+      light_sensor_port_.get(), light_sensor_service_, kIOGeneralInterest,
+      IOServiceCallback, this, light_sensor_notification_.InitializeInto());
+  if (kr != KERN_SUCCESS)
+    return false;
+
+  kr = IOServiceOpen(light_sensor_service_, mach_task_self(), 0,
+                     light_sensor_object_.InitializeInto());
+
+  return kr == KERN_SUCCESS;
+}
+
+void PlatformSensorAmbientLightMac::StopSensor() {
+  light_sensor_port_.reset();
+  light_sensor_notification_.reset();
+  light_sensor_object_.reset();
+  current_lux_ = 0;

[Mikhail, 2016/10/06 19:52:54]

nit: = 0.0;

+}
+
+void PlatformSensorAmbientLightMac::UpdateReading(uint64_t lux_values[2]) {
+  uint64_t mean = (lux_values[0] + lux_values[1]) / 2;
+  double lux = LMUvalueToLux(mean);
+  if (lux == current_lux_)
+    return;
+  current_lux_ = lux;
+
+  mojom::SensorReading reading;
+  reading.timestamp = (base::TimeTicks::Now() - base::TimeTicks()).InSecondsF();
+  reading.value1 = current_lux_;
+  UpdateSensorReading(reading);
+
+  task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&PlatformSensorAmbientLightMac::NotifySensorReadingChanged,
+                 this));
+}
+
+}  // namespace device