system/hwc3/DrmEventListener.cpp

/*
 * Copyright 2022 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 "DrmEventListener.h"

#include <linux/netlink.h>
#include <sys/socket.h>

namespace aidl::android::hardware::graphics::composer3::impl {

std::unique_ptr<DrmEventListener> DrmEventListener::create(::android::base::borrowed_fd drmFd,
                                                           std::function<void()> callback) {
    std::unique_ptr<DrmEventListener> listener(new DrmEventListener(std::move(callback)));

    if (!listener->init(drmFd)) {
        return nullptr;
    }

    return listener;
}

bool DrmEventListener::init(::android::base::borrowed_fd drmFd) {
    mEventFd = ::android::base::unique_fd(socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT));
    if (!mEventFd.ok()) {
        ALOGE("Failed to open uevent socket: %s", strerror(errno));
        return false;
    }
    struct sockaddr_nl addr;
    memset(&addr, 0, sizeof(addr));
    addr.nl_family = AF_NETLINK;
    addr.nl_pid = 0;
    addr.nl_groups = 0xFFFFFFFF;

    int ret = bind(mEventFd, (struct sockaddr*)&addr, sizeof(addr));
    if (ret) {
        ALOGE("Failed to bind uevent socket: %s", strerror(errno));
        return false;
    }

    FD_ZERO(&mMonitoredFds);
    FD_SET(drmFd.get(), &mMonitoredFds);
    FD_SET(mEventFd.get(), &mMonitoredFds);
    mMaxMonitoredFd = std::max(drmFd.get(), mEventFd.get());

    mThread = std::thread([this]() { threadLoop(); });

    return true;
}

void DrmEventListener::threadLoop() {
    int ret;
    do {
        ret = select(mMaxMonitoredFd + 1, &mMonitoredFds, NULL, NULL, NULL);
    } while (ret == -1 && errno == EINTR);

    if (!FD_ISSET(mEventFd.get(), &mMonitoredFds)) {
        ALOGE("%s: DrmEventListevener event fd unset?", __FUNCTION__);
        return;
    }

    char buffer[1024];
    while (true) {
        ret = read(mEventFd.get(), &buffer, sizeof(buffer));
        if (ret == 0) {
            return;
        } else if (ret < 0) {
            ALOGE("Got error reading uevent %d", ret);
            return;
        }

        bool drmEvent = false, hotplugEvent = false;
        for (int i = 0; i < ret;) {
            char* event = buffer + i;
            if (strcmp(event, "DEVTYPE=drm_minor")) {
                drmEvent = true;
            } else if (strcmp(event, "HOTPLUG=1")) {
                hotplugEvent = true;
            }

            i += strlen(event) + 1;
        }

        if (drmEvent && hotplugEvent) {
            DEBUG_LOG("DrmEventListener detected hotplug event .");
            mOnEventCallback();
        }
    }
}

}  // namespace aidl::android::hardware::graphics::composer3::impl