chromeos: Add CPU temperature reader

chromeos/system/cpu_temperature_reader.cc

Index: chromeos/system/cpu_temperature_reader.cc
diff --git a/chromeos/system/cpu_temperature_reader.cc b/chromeos/system/cpu_temperature_reader.cc
new file mode 100644
index 0000000000000000000000000000000000000000..94fd0fda77db7d2bcb8359dc284067e97d3c3950
--- /dev/null
+++ b/chromeos/system/cpu_temperature_reader.cc
@@ -0,0 +1,107 @@
+// 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.
+
+#include "chromeos/system/cpu_temperature_reader.h"
+
+#include "base/files/file_enumerator.h"
+#include "base/files/file_path.h"
+#include "base/files/file_util.h"
+#include "base/location.h"
+#include "base/strings/string_number_conversions.h"
+#include "base/strings/string_util.h"
+#include "base/task_scheduler/post_task.h"
+#include "base/task_scheduler/task_traits.h"
+
+namespace chromeos {
+namespace system {
+
+namespace {
+
+// The location we read our CPU temperature and channel label from.
+const char kDefaultHwmonDir[] = "/sys/class/hwmon/";

[Daniel Erat, 2017/04/20 21:23:52]

nit: use constexpr char for all of these

[Simon Que, 2017/04/21 08:52:25]

Done.

+const char kDeviceDir[] = "device";
+const char kHwmonDirectoryPattern[] = "hwmon*";
+const char kCPUTempFilePattern[] = "temp*_input";
+
+using CPUTemperatureInfo = CPUTemperatureReader::CPUTemperatureInfo;

[Daniel Erat, 2017/04/20 21:23:52]

move this up outside of the anon namespace (it feels a bit weird to me to put it
here)

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

Done.

+
+bool ReadTemperatureFromPath(const base::FilePath& path, double* temp_celsius) {

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

temp_celsius_out

[Simon Que, 2017/04/21 08:52:25]

Done.

+  std::string temperature_string;
+  uint32_t temperature = 0;
+  if (base::ReadFileToString(path, &temperature_string) &&
+      base::StringToUint(temperature_string, &temperature)) {
+    *temp_celsius = static_cast<double>(temperature) / 1000;

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

instead of static_cast, you can probably just divide the uint32_t by 1000.0

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

Done.

+    return true;
+  }
+  return false;
+}
+
+std::string GetLabelFromPath(const base::FilePath& label_path) {
+  // Get the label describing this temperature. Use temp*_label
+  // if present, fall back on name file or blank.
+  std::string label;
+  if (base::PathExists(base::FilePath(label_path))) {
+    base::ReadFileToString(base::FilePath(label_path), &label);
+    return label;
+  }
+
+  base::FilePath name_path = label_path.DirName().Append("name");
+  if (base::PathExists(base::FilePath(name_path))) {
+    base::ReadFileToString(name_path, &label);
+  }
+  return label;

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

returning an empty string feels a bit strange. would it be better to just return
the original path if we can't find anything else?

[Simon Que, 2017/04/21 08:52:25]

Done.

+}
+
+std::vector<CPUTemperatureInfo> ReadCPUTemperatures(
+    const std::string& hwmon_dir) {
+  std::vector<CPUTemperatureInfo> result;
+
+  // Get directories /sys/class/hwmon/hwmon*

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

nit: add trailing period

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

Done.

+  base::FileEnumerator hwmon_enumerator(base::FilePath(hwmon_dir), false,
+                                        base::FileEnumerator::DIRECTORIES,
+                                        kHwmonDirectoryPattern);
+  for (base::FilePath hwmon_path = hwmon_enumerator.Next(); !hwmon_path.empty();
+       hwmon_path = hwmon_enumerator.Next()) {
+    // Get temp*_input files in hwmon*/ and hwmon*/device/

[Daniel Erat, 2017/04/20 21:23:52]

nit: add trailing period

[Simon Que, 2017/04/21 08:52:25]

Done.

+    if (base::PathExists(hwmon_path.Append(kDeviceDir))) {
+      hwmon_path = hwmon_path.Append(kDeviceDir);
+    }
+    base::FileEnumerator enumerator(
+        hwmon_path, false, base::FileEnumerator::FILES, kCPUTempFilePattern);
+    for (base::FilePath temperature_path = enumerator.Next();
+         !temperature_path.empty(); temperature_path = enumerator.Next()) {
+      // Get appropriate temp*_label file.
+      std::string label_path = temperature_path.MaybeAsASCII();
+      if (label_path.empty()) {
+        LOG(WARNING) << "Unable to parse a path to temp*_input file as ASCII";
+        continue;
+      }
+      CPUTemperatureInfo info;
+      if (!ReadTemperatureFromPath(temperature_path, &info.temp_celsius)) {
+        LOG(WARNING) << "Unable to read CPU temperature from " << label_path;
+        continue;
+      }
+      base::ReplaceSubstringsAfterOffset(&label_path, 0, "input", "label");
+      info.label = GetLabelFromPath(base::FilePath(label_path));
+      result.push_back(info);
+    }
+  }
+  return result;
+}
+
+}  // namespace
+
+CPUTemperatureReader::CPUTemperatureReader() : hwmon_dir_(kDefaultHwmonDir) {}
+
+void CPUTemperatureReader::GetCPUTemperatures(
+    const GetCPUTemperaturesCallback& callback) {
+  base::PostTaskWithTraitsAndReplyWithResult(
+      FROM_HERE,
+      base::TaskTraits().MayBlock().WithPriority(
+          base::TaskPriority::BACKGROUND),
+      base::Bind(&ReadCPUTemperatures, hwmon_dir_), callback);
+}
+
+}  // namespace system
+}  // namespace chromeos