peripheralmanager/daemon/led_driver_sysfs.cc

/*
 * Copyright (C) 2016 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "led_driver_sysfs.h"

#include <fcntl.h>
#include <string>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include <base/logging.h>

namespace android {
namespace {

const char kSysfsLedPathPrefix[] = "/sys/class/leds/";
const char kMaxBrightnessFilename[] = "max_brightness";
const char kBrightnessFilename[] = "brightness";

}  // namespace

LedDriverSysfs::LedDriverSysfs(std::string* prefix)
    : fd_(-1), prefix_(prefix) {}

LedDriverSysfs::~LedDriverSysfs() {
  if (fd_ >= 0) {
    close(fd_);
  }
}

bool LedDriverSysfs::Init(const std::string& name) {
  LOG(INFO) << "Opening " << name;

  // If a custom prefix was defined, use it.
  std::string path = prefix_ ? *prefix_ + name : kSysfsLedPathPrefix + name;

  int fd = open(path.c_str(), O_RDONLY);
  if (fd < 0) {
    PLOG(WARNING) << "Failed to open " << path;
    return false;
  }

  fd_ = fd;
  return true;
}

bool LedDriverSysfs::SetBrightness(uint32_t val) {
  return WriteToFile(kBrightnessFilename, std::to_string(val));
}

bool LedDriverSysfs::GetBrightness(uint32_t* val) {
  std::string str_val;
  if (!ReadFromFile(kBrightnessFilename, &str_val))
    return false;
  *val = std::stoi(str_val);
  return true;
}

bool LedDriverSysfs::GetMaxBrightness(uint32_t* val) {
  std::string str_val;
  if (!ReadFromFile(kMaxBrightnessFilename, &str_val))
    return false;
  *val = std::stoi(str_val);
  return true;
}

bool LedDriverSysfs::ReadFromFile(const std::string& file, std::string* value) {
  int fd = openat(fd_, file.c_str(), O_RDONLY);
  if (fd < 0)
    return false;
  char tmp_buf[16] = "";
  ssize_t bytes = read(fd, tmp_buf, sizeof(tmp_buf));
  close(fd);
  if (bytes < 0)
    return false;
  value->assign(tmp_buf, bytes);
  return true;
}

bool LedDriverSysfs::WriteToFile(const std::string& file,
                                 const std::string& value) {
  int fd = openat(fd_, file.c_str(), O_RDWR);
  if (fd < 0)
    return false;

  ssize_t bytes = write(fd, value.c_str(), value.size());
  close(fd);
  if (bytes < 0)
    return false;
  if ((size_t)bytes != value.size())
    return false;
  return true;
}

}  // namespace android