Reland "[On-device adaptive brightness] Implement an AlsReader to ambient light."

Original change's description:
> Revert "[On-device adaptive brightness] Implement an AlsReader to ambient light."
> 
> This reverts commit ea692f36.
> 
> Reason for revert: broke the linux-chromeos-dbg (https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/linux-chromeos-dbg/7744)
> 
> Original change's description:
> > [On-device adaptive brightness] Implement an AlsReader to ambient light.
> > 
> > 
> > Bug: 881215
> > Change-Id: I1cd5bf7ea517e426b54df1f4ebbb5a843b991dbe
> > Reviewed-on: https://chromium-review.googlesource.com/1209000
> > Reviewed-by: Michael Martis <martis@chromium.org>
> > Reviewed-by: Dan Erat <derat@chromium.org>
> > Commit-Queue: Jia Meng <jiameng@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#589843}
> 
> TBR=derat@chromium.org,jiameng@chromium.org,martis@chromium.org
> 
> Change-Id: Id12029b7d3b46eaed672525fe0bcf96960ea143c
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Bug: 881215
> Reviewed-on: https://chromium-review.googlesource.com/1215603
> Reviewed-by: Jia Meng <jiameng@chromium.org>
> Commit-Queue: Jia Meng <jiameng@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#589850}

TBR=derat@chromium.org,jiameng@chromium.org,martis@chromium.org

Change-Id: I8f170731509b2b23d469519fd45d5876175111d5
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 881215
Reviewed-on: https://chromium-review.googlesource.com/1217962Reviewed-by: Jia Meng <jiameng@chromium.org>
Commit-Queue: Jia Meng <jiameng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#590115}

chrome/browser/chromeos/BUILD.gn

@@ -1580,6 +1580,8 @@ source_set("chromeos") {
     "policy/weekly_time/weekly_time_interval.h",
     "policy/wildcard_login_checker.cc",
     "policy/wildcard_login_checker.h",
+    "power/auto_screen_brightness/als_reader.cc",
+    "power/auto_screen_brightness/als_reader.h",
     "power/cpu_data_collector.cc",
     "power/cpu_data_collector.h",
     "power/extension_event_observer.cc",
@@ -2253,6 +2255,7 @@ source_set("unit_tests") {
     "policy/weekly_time/time_utils_unittest.cc",
     "policy/weekly_time/weekly_time_interval_unittest.cc",
     "policy/weekly_time/weekly_time_unittest.cc",
+    "power/auto_screen_brightness/als_reader_unittest.cc",
     "power/cpu_data_collector_unittest.cc",
     "power/extension_event_observer_unittest.cc",
     "power/ml/adaptive_screen_brightness_manager_unittest.cc",

chrome/browser/chromeos/power/auto_screen_brightness/als_reader.cc

+// Copyright 2018 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 "chrome/browser/chromeos/power/auto_screen_brightness/als_reader.h"
+
+#include "base/command_line.h"
+#include "base/files/file_util.h"
+#include "base/macros.h"
+#include "base/process/launch.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_split.h"
+#include "base/strings/string_util.h"
+#include "base/task/post_task.h"
+#include "content/public/browser/browser_thread.h"
+
+namespace chromeos {
+namespace power {
+namespace auto_screen_brightness {
+
+namespace {
+// Returns whether the device has an ALS that we can use. This should run in
+// another thread to be non-blocking to the main thread.
+bool IsAlsEnabled() {
+  DCHECK(!content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+  base::CommandLine command_line{
+      base::FilePath(FILE_PATH_LITERAL("check_powerd_config"))};
+  command_line.AppendArg("--ambient_light_sensor");
+  int exit_code = 0;
+  std::string output;  // Not used.
+  const bool result =
+      base::GetAppOutputWithExitCode(command_line, &output, &exit_code);
+
+  if (!result) {
+    LOG(ERROR) << "Cannot run check_powerd_config --ambient_light_sensor";
+    return false;
+  }
+  return exit_code == 0;
+}
+
+// Returns whether the ALS step config is what we need. This function is only
+// called if an ALS is enabled. This should run in another thread to be
+// non-blocking to the main thread.
+// TODO(jiameng): we assume one specific device now, and only check if the
+// number of steps is 7.
+bool VerifyAlsConfig() {
+  DCHECK(!content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+  base::CommandLine command_line{
+      base::FilePath(FILE_PATH_LITERAL("check_powerd_config"))};
+  command_line.AppendArg("--internal_backlight_ambient_light_steps");
+  int exit_code = 0;
+  std::string output;
+  const bool result =
+      base::GetAppOutputWithExitCode(command_line, &output, &exit_code);
+
+  if (!result || exit_code != 0) {
+    LOG(ERROR) << "Cannot run check_powerd_config "
+                  "--internal_backlight_ambient_light_steps";
+    return false;
+  }
+
+  const std::vector<base::StringPiece> num_steps = base::SplitStringPiece(
+      output, "\n", base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
+  return num_steps.size() == 7;
+}
+
+// Returns ALS path. This should run in another thread to be non-blocking to the
+// main thread.
+std::string GetAlsPath() {
+  DCHECK(!content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+  base::CommandLine command_line{
+      base::FilePath(FILE_PATH_LITERAL("backlight_tool"))};
+  command_line.AppendArg("--get_ambient_light_path");
+  int exit_code = 0;
+  std::string output;
+  const bool result =
+      base::GetAppOutputWithExitCode(command_line, &output, &exit_code);
+  if (!result) {
+    LOG(ERROR) << "Cannot run backlight_tool --get_ambient_light_path";
+    return "";
+  }
+
+  if (exit_code != 0 || output.empty()) {
+    LOG(ERROR) << "Missing ambient light path";
+    return "";
+  }
+
+  return output;
+}
+
+// Reads ALS value from |ambient_light_path|. This should run in another thread
+// to be non-blocking to the main thread.
+std::string ReadAlsFromFile(const base::FilePath& ambient_light_path) {
+  DCHECK(!content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
+  std::string data;
+  if (!base::ReadFileToString(ambient_light_path, &data)) {
+    LOG(ERROR) << "Cannot read ALS value";
+    return "";
+  }
+  return data;
+}
+}  // namespace
+
+constexpr int AlsReader::kMaxInitialAttempts;
+
+AlsReader::AlsReader()
+    : als_task_runner_(base::CreateSequencedTaskRunnerWithTraits(
+          {base::TaskPriority::BEST_EFFORT, base::MayBlock(),
+           base::TaskShutdownBehavior::SKIP_ON_SHUTDOWN})),
+      weak_ptr_factory_(this) {}
+
+AlsReader::~AlsReader() = default;
+
+void AlsReader::AddObserver(Observer* const observer) {
+  DCHECK(observer);
+  observers_.AddObserver(observer);
+}
+
+void AlsReader::RemoveObserver(Observer* const observer) {
+  DCHECK(observer);
+  observers_.RemoveObserver(observer);
+}
+
+AlsReader::AlsInitStatus AlsReader::GetInitStatus() const {
+  return status_;
+}
+
+void AlsReader::Init() {
+  base::PostTaskAndReplyWithResult(
+      als_task_runner_.get(), FROM_HERE, base::BindOnce(&IsAlsEnabled),
+      base::BindOnce(&AlsReader::OnAlsEnableCheckDone, AsWeakPtr()));
+}
+
+void AlsReader::SetTaskRunnerForTesting(
+    const scoped_refptr<base::SequencedTaskRunner> task_runner) {
+  als_task_runner_ = task_runner;
+  als_timer_.SetTaskRunner(task_runner);
+}
+
+void AlsReader::InitForTesting(const base::FilePath& ambient_light_path) {
+  DCHECK(!ambient_light_path.empty());
+  ambient_light_path_ = ambient_light_path;
+  status_ = AlsInitStatus::kSuccess;
+  OnInitializationComplete();
+  ReadAlsPeriodically();
+}
+
+base::WeakPtr<AlsReader> AlsReader::AsWeakPtr() {
+  return weak_ptr_factory_.GetWeakPtr();
+}
+
+void AlsReader::OnAlsEnableCheckDone(const bool is_enabled) {
+  if (!is_enabled) {
+    status_ = AlsInitStatus::kDisabled;
+    OnInitializationComplete();
+    return;
+  }
+
+  base::PostTaskAndReplyWithResult(
+      als_task_runner_.get(), FROM_HERE, base::BindOnce(&VerifyAlsConfig),
+      base::BindOnce(&AlsReader::OnAlsConfigCheckDone, AsWeakPtr()));
+}
+
+void AlsReader::OnAlsConfigCheckDone(const bool is_config_valid) {
+  if (!is_config_valid) {
+    status_ = AlsInitStatus::kIncorrectConfig;
+    OnInitializationComplete();
+    return;
+  }
+
+  RetryAlsPath();
+}
+
+void AlsReader::OnAlsPathReadAttempted(const std::string& path) {
+  if (!path.empty()) {
+    ambient_light_path_ = base::FilePath(path);
+    status_ = AlsInitStatus::kSuccess;
+    OnInitializationComplete();
+    ReadAlsPeriodically();
+    return;
+  }
+
+  ++num_failed_initialization_;
+
+  if (num_failed_initialization_ == kMaxInitialAttempts) {
+    status_ = AlsInitStatus::kMissingPath;
+    OnInitializationComplete();
+    return;
+  }
+
+  als_timer_.Start(FROM_HERE, kAlsFileCheckingInterval, this,
+                   &AlsReader::RetryAlsPath);
+}
+
+void AlsReader::RetryAlsPath() {
+  base::PostTaskAndReplyWithResult(
+      als_task_runner_.get(), FROM_HERE, base::BindOnce(&GetAlsPath),
+      base::BindOnce(&AlsReader::OnAlsPathReadAttempted, AsWeakPtr()));
+}
+
+void AlsReader::OnInitializationComplete() {
+  DCHECK_NE(status_, AlsInitStatus::kInProgress);
+  for (auto& observer : observers_)
+    observer.OnAlsReaderInitialized(status_);
+}
+
+void AlsReader::ReadAlsPeriodically() {
+  base::PostTaskAndReplyWithResult(
+      als_task_runner_.get(), FROM_HERE,
+      base::BindOnce(&ReadAlsFromFile, ambient_light_path_),
+      base::BindOnce(&AlsReader::OnAlsRead, AsWeakPtr()));
+}
+
+void AlsReader::OnAlsRead(const std::string& data) {
+  std::string trimmed_data;
+  base::TrimWhitespaceASCII(data, base::TRIM_ALL, &trimmed_data);
+  int value = 0;
+  if (base::StringToInt(trimmed_data, &value)) {
+    for (auto& observer : observers_)
+      observer.OnAmbientLightUpdated(value);
+  }
+  als_timer_.Start(FROM_HERE, kAlsPollInterval, this,
+                   &AlsReader::ReadAlsPeriodically);
+}
+
+}  // namespace auto_screen_brightness
+}  // namespace power
+}  // namespace chromeos

chrome/browser/chromeos/power/auto_screen_brightness/als_reader.h

+// Copyright 2018 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 CHROME_BROWSER_CHROMEOS_POWER_AUTO_SCREEN_BRIGHTNESS_ALS_READER_H_
+#define CHROME_BROWSER_CHROMEOS_POWER_AUTO_SCREEN_BRIGHTNESS_ALS_READER_H_
+
+#include "base/files/file_path.h"
+#include "base/macros.h"
+#include "base/memory/scoped_refptr.h"
+#include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
+#include "base/sequenced_task_runner.h"
+#include "base/task_runner_util.h"
+#include "base/timer/timer.h"
+
+namespace chromeos {
+namespace power {
+namespace auto_screen_brightness {
+
+// AlsReader periodically reads lux values from the ambient light sensor (ALS)
+// if powerd has been configured to use it.
+class AlsReader {
+ public:
+  // ALS file location may not be ready immediately, so we retry every
+  // |kAlsFileCheckingInterval| until |kMaxInitialAttempts| is reached, then
+  // we give up.
+  static constexpr base::TimeDelta kAlsFileCheckingInterval =
+      base::TimeDelta::FromSeconds(1);
+  static constexpr int kMaxInitialAttempts = 20;
+
+  // Interval for polling ambient light values.
+  static constexpr base::TimeDelta kAlsPollInterval =
+      base::TimeDelta::FromSeconds(1);
+
+  // Status of AlsReader initialization.
+  enum class AlsInitStatus {
+    kSuccess = 0,
+    kInProgress = 1,
+    kDisabled = 2,
+    kIncorrectConfig = 3,
+    kMissingPath = 4,
+    kMaxValue = kMissingPath
+  };
+
+  // Observers should take WeakPtr of AlsReader and remove themselves in
+  // observers' destructors if AlsReader hasn't be destructed.
+  class Observer : public base::CheckedObserver {
+   public:
+    Observer() = default;
+    ~Observer() override = default;
+    virtual void OnAmbientLightUpdated(int lux) = 0;
+    virtual void OnAlsReaderInitialized(AlsInitStatus status) = 0;
+
+   private:
+    DISALLOW_COPY_AND_ASSIGN(Observer);
+  };
+
+  AlsReader();
+  ~AlsReader();
+
+  // Adds or removes an observer.
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
+  // An observer can call this method to check if ALS has been properly
+  // initialized and ready to use.
+  AlsInitStatus GetInitStatus() const;
+
+  // Checks if an ALS is enabled, and if the config is valid . Also
+  // reads ambient light file path.
+  void Init();
+
+  // Sets the task runner for testing purpose.
+  void SetTaskRunnerForTesting(
+      scoped_refptr<base::SequencedTaskRunner> task_runner);
+
+  // Sets ambient light path for testing purpose and initialize. This will cause
+  // all the checks to be skipped, i.e. whether ALS is enabled and if config is
+  // valid.
+  void InitForTesting(const base::FilePath& ambient_light_path);
+
+  base::WeakPtr<AlsReader> AsWeakPtr();
+
+ private:
+  friend class AlsReaderTest;
+
+  // Called when we've checked whether ALS is enabled.
+  void OnAlsEnableCheckDone(bool is_enabled);
+
+  // Called when we've checked whether ALS config is valid.
+  void OnAlsConfigCheckDone(bool is_config_valid);
+
+  // Called when we've tried to read ALS path. If |path| is empty, it would
+  // reschedule another attempt up to |kMaxInitialAttempts|.
+  void OnAlsPathReadAttempted(const std::string& path);
+
+  // Tries to read ALS path.
+  void RetryAlsPath();
+
+  // Notifies all observers with |status_| after AlsReader is initialized.
+  void OnInitializationComplete();
+
+  // Polls ambient light periodically and notifies all observers if a sample is
+  // read.
+  void ReadAlsPeriodically();
+
+  // This is called after ambient light (represented as |data|) is sampled. It
+  // parses |data| to int, notifies its observers and starts |als_timer_| for
+  // next sample.
+  void OnAlsRead(const std::string& data);
+
+  AlsInitStatus status_ = AlsInitStatus::kInProgress;
+  base::FilePath ambient_light_path_;
+  int num_failed_initialization_ = 0;
+
+  // Timer used to retry initialization and also for periodic ambient light
+  // sampling.
+  base::OneShotTimer als_timer_;
+  scoped_refptr<base::SequencedTaskRunner> als_task_runner_;
+  base::ObserverList<Observer> observers_;
+  base::WeakPtrFactory<AlsReader> weak_ptr_factory_;
+
+  DISALLOW_COPY_AND_ASSIGN(AlsReader);
+};
+
+}  // namespace auto_screen_brightness
+}  // namespace power
+}  // namespace chromeos
+
+#endif  // CHROME_BROWSER_CHROMEOS_POWER_AUTO_SCREEN_BRIGHTNESS_ALS_READER_H_

chrome/browser/chromeos/power/auto_screen_brightness/als_reader_unittest.cc

+// Copyright 2018 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 "chrome/browser/chromeos/power/auto_screen_brightness/als_reader.h"
+
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
+#include "base/files/scoped_temp_dir.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/test/scoped_task_environment.h"
+#include "base/threading/sequenced_task_runner_handle.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace chromeos {
+namespace power {
+namespace auto_screen_brightness {
+
+namespace {
+
+class TestObserver : public AlsReader::Observer {
+ public:
+  TestObserver() {}
+  ~TestObserver() override = default;
+
+  // AlsReader::Observer overrides:
+  void OnAmbientLightUpdated(const int lux) override {
+    ambient_light_ = lux;
+    ++num_received_ambient_lights_;
+  }
+
+  void OnAlsReaderInitialized(const AlsReader::AlsInitStatus status) override {
+    status_ = base::Optional<AlsReader::AlsInitStatus>(status);
+  }
+
+  int get_ambient_light() { return ambient_light_; }
+  int get_num_received_ambient_lights() { return num_received_ambient_lights_; }
+
+  AlsReader::AlsInitStatus get_status() {
+    CHECK(status_);
+    return status_.value();
+  }
+
+ private:
+  int ambient_light_ = -1;
+  int num_received_ambient_lights_ = 0;
+  base::Optional<AlsReader::AlsInitStatus> status_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestObserver);
+};
+}  // namespace
+
+class AlsReaderTest : public testing::Test {
+ public:
+  AlsReaderTest()
+      : scoped_task_environment_(
+            std::make_unique<base::test::ScopedTaskEnvironment>(
+                base::test::ScopedTaskEnvironment::MainThreadType::MOCK_TIME)) {
+    CHECK(temp_dir_.CreateUniqueTempDir());
+    ambient_light_path_ = temp_dir_.GetPath().Append("test_als");
+    als_reader_.SetTaskRunnerForTesting(base::SequencedTaskRunnerHandle::Get());
+    als_reader_.AddObserver(&test_observer_);
+    als_reader_.InitForTesting(ambient_light_path_);
+  }
+
+  ~AlsReaderTest() override = default;
+
+ protected:
+  void WriteLux(int lux) {
+    const std::string lux_string = base::IntToString(lux);
+    const int bytes_written = base::WriteFile(
+        ambient_light_path_, lux_string.data(), lux_string.size());
+    ASSERT_EQ(bytes_written, static_cast<int>(lux_string.size()))
+        << "Wrote " << bytes_written << " byte(s) instead of "
+        << lux_string.size() << " to " << ambient_light_path_.value();
+  }
+
+  base::ScopedTempDir temp_dir_;
+  base::FilePath ambient_light_path_;
+
+  std::unique_ptr<base::test::ScopedTaskEnvironment> scoped_task_environment_;
+
+  TestObserver test_observer_;
+  AlsReader als_reader_;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(AlsReaderTest);
+};
+
+TEST_F(AlsReaderTest, CheckInitStatusAlsFileFound) {
+  EXPECT_EQ(AlsReader::AlsInitStatus::kSuccess, als_reader_.GetInitStatus());
+}
+
+TEST_F(AlsReaderTest, OnAlsReaderInitialized) {
+  EXPECT_EQ(AlsReader::AlsInitStatus::kSuccess, test_observer_.get_status());
+}
+
+TEST_F(AlsReaderTest, OneAlsValue) {
+  WriteLux(10);
+  scoped_task_environment_->RunUntilIdle();
+  EXPECT_EQ(10, test_observer_.get_ambient_light());
+  EXPECT_EQ(1, test_observer_.get_num_received_ambient_lights());
+}
+
+TEST_F(AlsReaderTest, TwoAlsValues) {
+  WriteLux(10);
+  // Ambient light is read immediately after initialization, and then
+  // periodically every |kAlsPollInterval|. Below we move time for half of
+  // |kAlsPollInterval| to ensure there is only one reading attempt.
+  scoped_task_environment_->FastForwardBy(AlsReader::kAlsPollInterval / 2);
+  EXPECT_EQ(10, test_observer_.get_ambient_light());
+  EXPECT_EQ(1, test_observer_.get_num_received_ambient_lights());
+
+  WriteLux(20);
+  // Now move time for another |kAlsPollInterval| to trigger another read.
+  scoped_task_environment_->FastForwardBy(AlsReader::kAlsPollInterval);
+  EXPECT_EQ(20, test_observer_.get_ambient_light());
+  EXPECT_EQ(2, test_observer_.get_num_received_ambient_lights());
+}
+
+}  // namespace auto_screen_brightness
+}  // namespace power
+}  // namespace chromeos