chromeos: Add CPU temperature reader

chromeos/system/cpu_temperature_reader.h

Index: chromeos/system/cpu_temperature_reader.h
diff --git a/chromeos/system/cpu_temperature_reader.h b/chromeos/system/cpu_temperature_reader.h
new file mode 100644
index 0000000000000000000000000000000000000000..7fb3dbc30d720bd9af2cdd2a4b962fd0770af991
--- /dev/null
+++ b/chromeos/system/cpu_temperature_reader.h
@@ -0,0 +1,61 @@
+// Copyright 2017 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 CHROMEOS_SYSTEM_CPU_TEMPERATURE_READER_H_
+#define CHROMEOS_SYSTEM_CPU_TEMPERATURE_READER_H_
+
+#include <string>
+#include <utility>
+#include <vector>
+
+#include "base/bind.h"
+#include "base/callback.h"
+#include "base/macros.h"
+
+namespace chromeos {
+namespace system {
+
+// Used to read CPU temperature info from sysfs hwmon.
+class CPUTemperatureReader {
+ public:
+  // Contains info from a CPU temperature sensor.
+  struct CPUTemperatureInfo {
+    // The temperature read by a CPU temperature sensor in degrees Celsius.
+    double temp_celsius;
+
+    // The name of the CPU temperature zone monitored by this sensor. Used to
+    // identify the source of each temperature reading. Taken from sysfs "name"
+    // or "label" field, if it exists.
+    std::string label;
+
+    bool operator<(const CPUTemperatureInfo& other) const {
+      return std::make_pair(temp_celsius, label) <
+             std::make_pair(other.temp_celsius, label);
+    }
+  };
+
+  using GetCPUTemperaturesCallback =
+      base::Callback<void(const std::vector<CPUTemperatureInfo>&)>;
+
+  CPUTemperatureReader();

[Daniel Erat, 2017/04/20 21:23:53]

declare a d'tor here and define it in the .cc file

[Simon Que, 2017/04/21 08:52:26]

Done.

+
+  // Read temperature from each thermal sensor of the CPU. Returns a vector
+  // containing a reading from each sensor to |callback|. This function can be

[Daniel Erat, 2017/04/20 21:23:53]

nit: change second sentence to "Asynchronously runs |callback| with a reading
from each sensor."

[Simon Que, 2017/04/21 08:52:26]

Done.

+  // called on the main UI thread.
+  void GetCPUTemperatures(const GetCPUTemperaturesCallback& callback);
+
+  void set_hwmon_dir_for_test(const std::string& dir) { hwmon_dir_ = dir; }

[Daniel Erat, 2017/04/20 21:23:53]

nit: inline getters/setters usually come after d'tor and before non-inline
methods

[Simon Que, 2017/04/21 08:52:26]

Done.

+
+ private:
+  // Sysfs hwmon directory path. Gets initialized to a default value but can be
+  // overriden by set_hwmon_dir_for_test().

[Daniel Erat, 2017/04/20 21:23:53]

nit: don't need second sentence

[Simon Que, 2017/04/21 08:52:26]

Done.

+  std::string hwmon_dir_;
+
+  DISALLOW_COPY_AND_ASSIGN(CPUTemperatureReader);
+};
+
+}  // namespace system
+}  // namespace chromeos
+
+#endif  // CHROMEOS_SYSTEM_CPU_TEMPERATURE_READER_H_