Accelerometer: find trigger name

chromeos/accelerometer/accelerometer_reader.cc

 // Copyright 2014 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/accelerometer/accelerometer_reader.h"
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <string>
@@ skipping 14 matching lines @@
 #include "base/task_runner_util.h"
 #include "base/threading/platform_thread.h"
 #include "base/threading/sequenced_worker_pool.h"
 #include "base/threading/thread_task_runner_handle.h"
 
 namespace chromeos {
 
 namespace {
 
 // Paths to access necessary data from the accelerometer device.
-const base::FilePath::CharType kAccelerometerTriggerPath[] =
-    FILE_PATH_LITERAL("/sys/bus/iio/devices/trigger0/trigger_now");
 const base::FilePath::CharType kAccelerometerDevicePath[] =
     FILE_PATH_LITERAL("/dev/cros-ec-accel");
 const base::FilePath::CharType kAccelerometerIioBasePath[] =
     FILE_PATH_LITERAL("/sys/bus/iio/devices/");
 
+// Trigger created by accelerometer-init.sh to query the sensors.
+const char kTriggerPrefix[] = "trigger";
+const char kTriggerName[] = "sysfstrig0\n";
+
+// Sysfs entry to trigger readings.
+const base::FilePath::CharType kTriggerNow[] = "trigger_now";
+
 // This is the per source scale file in use on kernels older than 3.18. We
 // should remove this when all devices having accelerometers are on kernel 3.18
 // or later or have been patched to use new format: http://crbug.com/510831
 const base::FilePath::CharType kLegacyScaleNameFormatString[] =
     "in_accel_%s_scale";
 
 // File within kAccelerometerDevicePath/device* which denotes a single scale to
 // be used across all axes.
 const base::FilePath::CharType kAccelerometerScaleFileName[] = "scale";
 
@@ skipping 106 matching lines @@
   };
 
   // Configuration structure for accelerometer device.
   struct ConfigurationData {
     ConfigurationData();
     ~ConfigurationData();
 
     // Number of accelerometers on device.
     size_t count;
 
+    // sysfs entry to trigger readings.
+    base::FilePath trigger_now;
+
     // Which accelerometers are present on device.
     bool has[ACCELEROMETER_SOURCE_COUNT];
 
     // Scale of accelerometers (i.e. raw value * scale = m/s^2).
     float scale[ACCELEROMETER_SOURCE_COUNT][3];
 
     // Index of each accelerometer axis in data stream.
     int index[ACCELEROMETER_SOURCE_COUNT][3];
 
     // The information for each accelerometer device to be read. In kernel 3.18
@@ skipping 55 matching lines @@
 
   // Check for accelerometer symlink which will be created by the udev rules
   // file on detecting the device.
   if (base::IsDirectoryEmpty(base::FilePath(kAccelerometerDevicePath))) {
     if (base::SysInfo::IsRunningOnChromeOS()) {
       LOG(WARNING) << "Accelerometer device directory is empty at "
                    << kAccelerometerDevicePath;
     }
     return;
   }
-  if (!base::PathExists(base::FilePath(kAccelerometerTriggerPath))) {
+
+  // Find trigger to use:
+  base::FileEnumerator trigger_dir(base::FilePath(kAccelerometerIioBasePath),
+                                   false, base::FileEnumerator::DIRECTORIES);
+  std::string prefix = kTriggerPrefix;
+  for (base::FilePath name = trigger_dir.Next(); !name.empty();
+       name = trigger_dir.Next()) {
+    if (name.BaseName().value().substr(0, prefix.size()) != prefix)
+      continue;
+    std::string trigger_name;
+    if (!base::ReadFileToString(name.Append("name"), &trigger_name)) {
+      if (base::SysInfo::IsRunningOnChromeOS()) {
+        LOG(WARNING) << "Unable to read the trigger name at " << name.value();
+      }
+      continue;
+    }
+    if (trigger_name == kTriggerName) {
+      base::FilePath trigger_now = name.Append(kTriggerNow);
+      if (!base::PathExists(trigger_now)) {
+        if (base::SysInfo::IsRunningOnChromeOS()) {
+          LOG(ERROR) << "Accelerometer trigger does not exist at "
+                     << trigger_now.value();
+        }
+        return;
+      } else {
+        configuration_.trigger_now = trigger_now;
+        break;
+      }
+    }
+  }
+  if (configuration_.trigger_now.empty()) {
     if (base::SysInfo::IsRunningOnChromeOS()) {
-      LOG(ERROR) << "Accelerometer trigger does not exist at"
-                 << kAccelerometerTriggerPath;
+      LOG(ERROR) << "Accelerometer trigger not found";
     }
     return;
   }
 
   base::FileEnumerator symlink_dir(base::FilePath(kAccelerometerDevicePath),
                                    false, base::FileEnumerator::FILES);
   bool legacy_cross_accel = false;
   for (base::FilePath name = symlink_dir.Next(); !name.empty();
        name = symlink_dir.Next()) {
     base::FilePath iio_device;
@@ skipping 162 matching lines @@
   configuration_.scale[ACCELEROMETER_SOURCE_SCREEN][2] *= -1.0f;
 
   configuration_.reading_data.push_back(reading_data);
   return true;
 }
 
 void AccelerometerFileReader::ReadFileAndNotify() {
   DCHECK(initialization_successful_);
 
   // Initiate the trigger to read accelerometers simultaneously
-  int bytes_written = base::WriteFile(
-      base::FilePath(kAccelerometerTriggerPath), "1\n", 2);
+  int bytes_written = base::WriteFile(configuration_.trigger_now, "1\n", 2);
   if (bytes_written < 2) {
     PLOG(ERROR) << "Accelerometer trigger failure: " << bytes_written;
     return;
   }
 
   // Read resulting sample from /dev/cros-ec-accel.
   update_ = new AccelerometerUpdate();
   for (auto reading_data : configuration_.reading_data) {
     int reading_size = reading_data.sources.size() * kSizeOfReading;
     DCHECK_GT(reading_size, 0);
@@ skipping 60 matching lines @@
 }
 
 AccelerometerReader::AccelerometerReader()
     : accelerometer_file_reader_(new AccelerometerFileReader()) {
 }
 
 AccelerometerReader::~AccelerometerReader() {
 }
 
 }  // namespace chromeos