146 lines
3.9 KiB
C++
146 lines
3.9 KiB
C++
/*
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* Copyright (C) 2022 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#pragma once
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#include <linux/netlink.h>
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#include <poll.h>
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#include <sys/eventfd.h>
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#include <sys/socket.h>
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#include <cerrno>
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#include <memory>
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#include <optional>
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#include <string>
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#include "utils/fd.h"
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#include "utils/log.h"
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namespace android::drm_hwcomposer {
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class UEvent {
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public:
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static auto CreateInstance() -> std::unique_ptr<UEvent> {
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auto fd = MakeUniqueFd(
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socket(PF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_KOBJECT_UEVENT));
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if (!fd) {
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ALOGE("Failed to open uevent socket: errno=%i", errno);
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return {};
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}
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struct sockaddr_nl addr {};
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addr.nl_family = AF_NETLINK;
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addr.nl_pid = 0;
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addr.nl_groups = UINT32_MAX;
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// NOLINTNEXTLINE(cppcoreguidelines-pro-type-cstyle-cast)
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const int ret = bind(*fd, (struct sockaddr *)&addr, sizeof(addr));
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if (ret != 0) {
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ALOGE("Failed to bind uevent socket: errno=%i", errno);
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return {};
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}
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auto stop_event_fd = MakeUniqueFd(eventfd(0, EFD_CLOEXEC));
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if (!stop_event_fd) {
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ALOGE("Failed to create eventfd: errno=%i", errno);
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return {};
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}
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return std::unique_ptr<UEvent>(new UEvent(fd, stop_event_fd));
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}
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auto ReadNext() -> std::optional<std::string> {
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constexpr int kUEventBufferSize = 1024;
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char buffer[kUEventBufferSize];
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if (!WaitForData()) {
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return {};
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}
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ssize_t ret = 0;
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ret = read(*fd_, &buffer, sizeof(buffer));
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if (ret == 0)
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return {};
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if (ret < 0) {
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ALOGE("Got error reading uevent %zd", ret);
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return {};
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}
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for (int i = 0; i < ret - 1; i++) {
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if (buffer[i] == '\0') {
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buffer[i] = '\n';
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}
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}
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return std::string(buffer, ret);
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}
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void Stop() {
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// Increment the eventfd by writing 1. All subsequent calls to ReadNext will
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// return false.
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const uint64_t value = 1;
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const ssize_t ret = write(*stop_event_fd_, &value, sizeof(value));
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if (ret == -1) {
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ALOGE("Error writing to eventfd. errno: %d", errno);
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} else if (ret != sizeof(value)) {
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ALOGE("Wrote fewer bytes to eventfd than expected: %zd vs %zd", ret,
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sizeof(value));
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}
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}
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private:
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enum { kFdIdx = 0, kStopEventFdIdx, kNumFds };
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UEvent(UniqueFd &fd, UniqueFd &stop_event_fd)
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: fd_(std::move(fd)), stop_event_fd_(std::move(stop_event_fd)) {};
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// Returns true if there is data to be read off of fd_.
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bool WaitForData() {
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struct pollfd poll_fds[kNumFds];
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poll_fds[kFdIdx].fd = *fd_;
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poll_fds[kFdIdx].events = POLLIN;
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poll_fds[kStopEventFdIdx].fd = *stop_event_fd_;
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poll_fds[kStopEventFdIdx].events = POLLIN;
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const int ret = poll(poll_fds, kNumFds, -1);
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if (ret == 0) {
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// Timeout shouldn't happen, but return here anyways.
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ALOGE("Timed out polling uevent.");
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return false;
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}
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if (ret < 1) {
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ALOGE("Error polling uevent. errno: %d", errno);
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return false;
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}
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if ((poll_fds[kStopEventFdIdx].revents & POLLIN) != 0) {
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// Stop event has been signalled. Return without reading from the fd to
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// ensure that this fd stays in a readable state.
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ALOGI("Stop event signalled.");
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return false;
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}
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// Return true if there is data to read.
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return (poll_fds[kFdIdx].revents & POLLIN) != 0;
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}
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UniqueFd fd_;
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UniqueFd stop_event_fd_;
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};
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} // namespace android::drm_hwcomposer
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