src/chromeos/accelerometer/accelerometer_reader.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "chromeos/accelerometer/accelerometer_reader.h"
   6
   7 #include "base/bind.h"
   8 #include "base/files/file_util.h"
   9 #include "base/location.h"
  10 #include "base/message_loop/message_loop.h"
  11 #include "base/strings/string_number_conversions.h"
  12 #include "base/strings/string_util.h"
  13 #include "base/strings/stringprintf.h"
  14 #include "base/task_runner.h"
  15 #include "base/task_runner_util.h"
  16 #include "base/threading/sequenced_worker_pool.h"
  17
  18 namespace chromeos {
  19
  20 namespace {
  21
  22 // Paths to access necessary data from the accelerometer device.
  23 const base::FilePath::CharType kAccelerometerTriggerPath[] =
  24     FILE_PATH_LITERAL("/sys/bus/iio/devices/trigger0/trigger_now");
  25 const base::FilePath::CharType kAccelerometerDevicePath[] =
  26     FILE_PATH_LITERAL("/dev/cros-ec-accel");
  27 const base::FilePath::CharType kAccelerometerIioBasePath[] =
  28     FILE_PATH_LITERAL("/sys/bus/iio/devices/");
  29
  30 // File within the device in kAccelerometerIioBasePath containing the scale of
  31 // the accelerometers.
  32 const base::FilePath::CharType kScaleNameFormatString[] = "in_accel_%s_scale";
  33
  34 // The filename giving the path to read the scan index of each accelerometer
  35 // axis.
  36 const char kAccelerometerScanIndexPath[] =
  37     "scan_elements/in_accel_%s_%s_index";
  38
  39 // The names of the accelerometers. Matches up with the enum AccelerometerSource
  40 // in ui/accelerometer/accelerometer_types.h.
  41 const char kAccelerometerNames[ui::ACCELEROMETER_SOURCE_COUNT][5] = {
  42     "lid", "base"};
  43
  44 // The axes on each accelerometer.
  45 const char kAccelerometerAxes[][2] = {"y", "x", "z"};
  46
  47 // The length required to read uint values from configuration files.
  48 const size_t kMaxAsciiUintLength = 21;
  49
  50 // The size of individual values.
  51 const size_t kDataSize = 2;
  52
  53 // The time to wait between reading the accelerometer.
  54 const int kDelayBetweenReadsMs = 100;
  55
  56 // The mean acceleration due to gravity on Earth in m/s^2.
  57 const float kMeanGravity = 9.80665f;
  58
  59 // Reads |path| to the unsigned int pointed to by |value|. Returns true on
  60 // success or false on failure.
  61 bool ReadFileToInt(const base::FilePath& path, int* value) {
  62   std::string s;
  63   DCHECK(value);
  64   if (!base::ReadFileToString(path, &s, kMaxAsciiUintLength)) {
  65     return false;
  66   }
  67   base::TrimWhitespaceASCII(s, base::TRIM_ALL, &s);
  68   if (!base::StringToInt(s, value)) {
  69     LOG(ERROR) << "Failed to parse \"" << s << "\" from " << path.value();
  70     return false;
  71   }
  72   return true;
  73 }
  74
  75 bool DetectAndReadAccelerometerConfiguration(
  76     scoped_refptr<AccelerometerReader::Configuration> configuration) {
  77   // Check for accelerometer symlink which will be created by the udev rules
  78   // file on detecting the device.
  79   base::FilePath device;
  80   if (!base::ReadSymbolicLink(base::FilePath(kAccelerometerDevicePath),
  81                               &device)) {
  82     return false;
  83   }
  84
  85   if (!base::PathExists(base::FilePath(kAccelerometerTriggerPath))) {
  86     LOG(ERROR) << "Accelerometer trigger does not exist at"
  87                << kAccelerometerTriggerPath;
  88     return false;
  89   }
  90
  91   base::FilePath iio_path(base::FilePath(kAccelerometerIioBasePath).Append(
  92       device));
  93   // Read configuration of each accelerometer axis from each accelerometer from
  94   // /sys/bus/iio/devices/iio:deviceX/.
  95   for (size_t i = 0; i < arraysize(kAccelerometerNames); ++i) {
  96     // Read scale of accelerometer.
  97     std::string accelerometer_scale_path = base::StringPrintf(
  98         kScaleNameFormatString, kAccelerometerNames[i]);
  99     int scale_divisor;
 100     if (!ReadFileToInt(iio_path.Append(accelerometer_scale_path.c_str()),
 101         &scale_divisor)) {
 102       configuration->data.has[i] = false;
 103       continue;
 104     }
 105
 106     configuration->data.has[i] = true;
 107     configuration->data.count++;
 108     for (size_t j = 0; j < arraysize(kAccelerometerAxes); ++j) {
 109       configuration->data.scale[i][j] = kMeanGravity / scale_divisor;
 110       std::string accelerometer_index_path = base::StringPrintf(
 111           kAccelerometerScanIndexPath, kAccelerometerAxes[j],
 112           kAccelerometerNames[i]);
 113       if (!ReadFileToInt(iio_path.Append(accelerometer_index_path.c_str()),
 114                          &(configuration->data.index[i][j]))) {
 115         return false;
 116       }
 117     }
 118   }
 119
 120   // Adjust the directions of accelerometers to match the AccelerometerUpdate
 121   // type specified in ui/accelerometer/accelerometer_types.h.
 122   configuration->data.scale[ui::ACCELEROMETER_SOURCE_SCREEN][0] *= -1.0f;
 123   for (int i = 0; i < 3; ++i) {
 124     configuration->data.scale[ui::ACCELEROMETER_SOURCE_ATTACHED_KEYBOARD][i] *=
 125         -1.0f;
 126   }
 127
 128   // Verify indices are within bounds.
 129   for (int i = 0; i < ui::ACCELEROMETER_SOURCE_COUNT; ++i) {
 130     if (!configuration->data.has[i])
 131       continue;
 132     for (int j = 0; j < 3; ++j) {
 133       if (configuration->data.index[i][j] < 0 ||
 134           configuration->data.index[i][j] >=
 135               3 * static_cast<int>(configuration->data.count)) {
 136         LOG(ERROR) << "Field index for " << kAccelerometerNames[i] << " "
 137                    << kAccelerometerAxes[j] << " axis out of bounds.";
 138         return false;
 139       }
 140     }
 141   }
 142   configuration->data.length = kDataSize * 3 * configuration->data.count;
 143   return true;
 144 }
 145
 146 bool ReadAccelerometer(
 147     scoped_refptr<AccelerometerReader::Reading> reading,
 148     size_t length) {
 149   // Initiate the trigger to read accelerometers simultaneously
 150   int bytes_written = base::WriteFile(
 151       base::FilePath(kAccelerometerTriggerPath), "1\n", 2);
 152   if (bytes_written < 2) {
 153     PLOG(ERROR) << "Accelerometer trigger failure: " << bytes_written;
 154     return false;
 155   }
 156
 157   // Read resulting sample from /dev/cros-ec-accel.
 158   int bytes_read = base::ReadFile(base::FilePath(kAccelerometerDevicePath),
 159                                   reading->data, length);
 160   if (bytes_read < static_cast<int>(length)) {
 161     LOG(ERROR) << "Read " << bytes_read << " byte(s), expected "
 162                << length << " bytes from accelerometer";
 163     return false;
 164   }
 165   return true;
 166 }
 167
 168 }  // namespace
 169
 170 AccelerometerReader::ConfigurationData::ConfigurationData()
 171     : count(0) {
 172   for (int i = 0; i < ui::ACCELEROMETER_SOURCE_COUNT; ++i) {
 173     has[i] = false;
 174     for (int j = 0; j < 3; ++j) {
 175       scale[i][j] = 0;
 176       index[i][j] = -1;
 177     }
 178   }
 179 }
 180
 181 AccelerometerReader::ConfigurationData::~ConfigurationData() {
 182 }
 183
 184 AccelerometerReader::AccelerometerReader(
 185     scoped_refptr<base::TaskRunner> blocking_task_runner,
 186     AccelerometerReader::Delegate* delegate)
 187     : task_runner_(blocking_task_runner),
 188       delegate_(delegate),
 189       configuration_(new AccelerometerReader::Configuration()),
 190       weak_factory_(this) {
 191   DCHECK(task_runner_.get());
 192   DCHECK(delegate_);
 193   // Asynchronously detect and initialize the accelerometer to avoid delaying
 194   // startup.
 195   base::PostTaskAndReplyWithResult(task_runner_.get(), FROM_HERE,
 196       base::Bind(&DetectAndReadAccelerometerConfiguration, configuration_),
 197       base::Bind(&AccelerometerReader::OnInitialized,
 198                  weak_factory_.GetWeakPtr(), configuration_));
 199 }
 200
 201 AccelerometerReader::~AccelerometerReader() {
 202 }
 203
 204 void AccelerometerReader::OnInitialized(
 205     scoped_refptr<AccelerometerReader::Configuration> configuration,
 206     bool success) {
 207   if (success)
 208     TriggerRead();
 209 }
 210
 211 void AccelerometerReader::TriggerRead() {
 212   DCHECK(!task_runner_->RunsTasksOnCurrentThread());
 213
 214   scoped_refptr<AccelerometerReader::Reading> reading(
 215       new AccelerometerReader::Reading());
 216   base::PostTaskAndReplyWithResult(task_runner_.get(),
 217                                    FROM_HERE,
 218                                    base::Bind(&ReadAccelerometer, reading,
 219                                               configuration_->data.length),
 220                                    base::Bind(&AccelerometerReader::OnDataRead,
 221                                               weak_factory_.GetWeakPtr(),
 222                                               reading));
 223 }
 224
 225 void AccelerometerReader::OnDataRead(
 226     scoped_refptr<AccelerometerReader::Reading> reading,
 227     bool success) {
 228   DCHECK(!task_runner_->RunsTasksOnCurrentThread());
 229
 230   if (success) {
 231     for (int i = 0; i < ui::ACCELEROMETER_SOURCE_COUNT; ++i) {
 232       if (!configuration_->data.has[i])
 233         continue;
 234
 235       int16* values = reinterpret_cast<int16*>(reading->data);
 236       update_.Set(static_cast<ui::AccelerometerSource>(i),
 237                   values[configuration_->data.index[i][0]] *
 238                       configuration_->data.scale[i][0],
 239                   values[configuration_->data.index[i][1]] *
 240                       configuration_->data.scale[i][1],
 241                   values[configuration_->data.index[i][2]] *
 242                       configuration_->data.scale[i][2]);
 243     }
 244     delegate_->HandleAccelerometerUpdate(update_);
 245   }
 246
 247   // Trigger another read after the current sampling delay.
 248   base::MessageLoop::current()->PostDelayedTask(
 249       FROM_HERE,
 250       base::Bind(&AccelerometerReader::TriggerRead,
 251                  weak_factory_.GetWeakPtr()),
 252       base::TimeDelta::FromMilliseconds(kDelayBetweenReadsMs));
 253 }
 254
 255 }  // namespace chromeos