1 /** 2 * Copyright (c) 2021, The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef CPP_LIBSYSFSMONITOR_SRC_SYSFSMONITOR_H_ 18 #define CPP_LIBSYSFSMONITOR_SRC_SYSFSMONITOR_H_ 19 20 #include <android-base/result.h> 21 #include <android-base/unique_fd.h> 22 #include <utils/RefBase.h> 23 24 #include <functional> 25 #include <string> 26 #include <thread> // NOLINT(build/c++11) 27 #include <unordered_set> 28 29 namespace android { 30 namespace automotive { 31 32 using CallbackFunc = ::std::function<void(const std::vector<int32_t>&)>; 33 34 /** 35 * SysfsMonitor monitors sysfs file changes and invokes the registered callback when there is a 36 * change at the sysfs files to monitor. 37 */ 38 class SysfsMonitor final : public RefBase { 39 public: 40 // Initializes SysfsMonitor instance. 41 android::base::Result<void> init(CallbackFunc callback); 42 // Releases resources used for monitoring. 43 android::base::Result<void> release(); 44 // Registers a sysfs file to monitor. 45 android::base::Result<void> registerFd(int32_t fd); 46 // Unregisters a sysfs file to monitor. 47 // Some events may be in process, so events may 48 // continue to be reported even after this method completes. 49 android::base::Result<void> unregisterFd(int32_t fd); 50 // Starts observing sysfs file changes. 51 android::base::Result<void> observe(); 52 53 private: 54 android::base::unique_fd mEpollFd; 55 std::unordered_set<int32_t> mMonitoringFds; 56 CallbackFunc mCallback; 57 std::thread mMonitoringThread; 58 int mPipefd[2]; 59 }; 60 61 } // namespace automotive 62 } // namespace android 63 64 #endif // CPP_LIBSYSFSMONITOR_SRC_SYSFSMONITOR_H_ 65