evs/sampleDriver/EvsEnumerator.cpp

/*
 * 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 "EvsEnumerator.h"
#include "EvsV4lCamera.h"
#include "EvsGlDisplay.h"
#include "ConfigManager.h"

#include <dirent.h>

#include <android-base/file.h>
#include <android-base/strings.h>
#include <android-base/stringprintf.h>
#include <hardware_legacy/uevent.h>
#include <hwbinder/IPCThreadState.h>
#include <cutils/android_filesystem_config.h>

using namespace std::chrono_literals;
using CameraDesc_1_0 = ::android::hardware::automotive::evs::V1_0::CameraDesc;
using CameraDesc_1_1 = ::android::hardware::automotive::evs::V1_1::CameraDesc;

namespace android {
namespace hardware {
namespace automotive {
namespace evs {
namespace V1_1 {
namespace implementation {


// NOTE:  All members values are static so that all clients operate on the same state
//        That is to say, this is effectively a singleton despite the fact that HIDL
//        constructs a new instance for each client.
std::unordered_map<std::string, EvsEnumerator::CameraRecord> EvsEnumerator::sCameraList;
wp<EvsGlDisplay>                                             EvsEnumerator::sActiveDisplay;
std::mutex                                                   EvsEnumerator::sLock;
std::condition_variable                                      EvsEnumerator::sCameraSignal;
std::unique_ptr<ConfigManager>                               EvsEnumerator::sConfigManager;
sp<IAutomotiveDisplayProxyService>                           EvsEnumerator::sDisplayProxy;
std::unordered_map<uint8_t, uint64_t>                        EvsEnumerator::sDisplayPortList;
uint64_t                                                     EvsEnumerator::sInternalDisplayId;


// Constants
const auto kEnumerationTimeout = 10s;


bool EvsEnumerator::checkPermission() {
    hardware::IPCThreadState *ipc = hardware::IPCThreadState::self();
    if (AID_AUTOMOTIVE_EVS != ipc->getCallingUid() &&
        AID_ROOT != ipc->getCallingUid()) {
        LOG(ERROR) << "EVS access denied: "
                   << "pid = " << ipc->getCallingPid()
                   << ", uid = " << ipc->getCallingUid();
        return false;
    }

    return true;
}

void EvsEnumerator::EvsUeventThread(std::atomic<bool>& running) {
    int status = uevent_init();
    if (!status) {
        LOG(ERROR) << "Failed to initialize uevent handler.";
        return;
    }

    char uevent_data[PAGE_SIZE - 2] = {};
    while (running) {
        int length = uevent_next_event(uevent_data, static_cast<int32_t>(sizeof(uevent_data)));

        // Ensure double-null termination.
        uevent_data[length] = uevent_data[length + 1] = '\0';

        const char *action = nullptr;
        const char *devname = nullptr;
        const char *subsys = nullptr;
        char *cp = uevent_data;
        while (*cp) {
            // EVS is interested only in ACTION, SUBSYSTEM, and DEVNAME.
            if (!std::strncmp(cp, "ACTION=", 7)) {
                action = cp + 7;
            } else if (!std::strncmp(cp, "SUBSYSTEM=", 10)) {
                subsys = cp + 10;
            } else if (!std::strncmp(cp, "DEVNAME=", 8)) {
                devname = cp + 8;
            }

            // Advance to after next \0
            while (*cp++);
        }

        if (!devname || !subsys || std::strcmp(subsys, "video4linux")) {
            // EVS expects that the subsystem of enabled video devices is
            // video4linux.
            continue;
        }

        // Update shared list.
        bool cmd_addition = !std::strcmp(action, "add");
        bool cmd_removal  = !std::strcmp(action, "remove");
        {
            std::string devpath = "/dev/";
            devpath += devname;

            std::lock_guard<std::mutex> lock(sLock);
            if (cmd_removal) {
                sCameraList.erase(devpath);
                LOG(INFO) << devpath << " is removed.";
            } else if (cmd_addition) {
                // NOTE: we are here adding new device without a validation
                // because it always fails to open, b/132164956.
                CameraRecord cam(devpath.c_str());
                if (sConfigManager != nullptr) {
                    unique_ptr<ConfigManager::CameraInfo> &camInfo =
                        sConfigManager->getCameraInfo(devpath);
                    if (camInfo != nullptr) {
                        cam.desc.metadata.setToExternal(
                            (uint8_t *)camInfo->characteristics,
                             get_camera_metadata_size(camInfo->characteristics)
                        );
                    }
                }
                sCameraList.emplace(devpath, cam);
                LOG(INFO) << devpath << " is added.";
            } else {
                // Ignore all other actions including "change".
            }

            // Notify the change.
            sCameraSignal.notify_all();
        }
    }

    return;
}

EvsEnumerator::EvsEnumerator(sp<IAutomotiveDisplayProxyService> proxyService) {
    LOG(DEBUG) << "EvsEnumerator is created.";

    if (sConfigManager == nullptr) {
        /* loads and initializes ConfigManager in a separate thread */
        sConfigManager =
            ConfigManager::Create();
    }

    if (sDisplayProxy == nullptr) {
        /* sets a car-window service handle */
        sDisplayProxy = proxyService;
    }

    enumerateCameras();
    enumerateDisplays();
}

void EvsEnumerator::enumerateCameras() {
    // For every video* entry in the dev folder, see if it reports suitable capabilities
    // WARNING:  Depending on the driver implementations this could be slow, especially if
    //           there are timeouts or round trips to hardware required to collect the needed
    //           information.  Platform implementers should consider hard coding this list of
    //           known good devices to speed up the startup time of their EVS implementation.
    //           For example, this code might be replaced with nothing more than:
    //                   sCameraList.emplace("/dev/video0");
    //                   sCameraList.emplace("/dev/video1");
    LOG(INFO) << __FUNCTION__
              << ": Starting dev/video* enumeration";
    unsigned videoCount   = 0;
    unsigned captureCount = 0;
    DIR* dir = opendir("/dev");
    if (!dir) {
        LOG_FATAL("Failed to open /dev folder\n");
    }
    struct dirent* entry;
    {
        std::lock_guard<std::mutex> lock(sLock);

        while ((entry = readdir(dir)) != nullptr) {
            // We're only looking for entries starting with 'video'
            if (strncmp(entry->d_name, "video", 5) == 0) {
                std::string deviceName("/dev/");
                deviceName += entry->d_name;
                videoCount++;
                if (sCameraList.find(deviceName) != sCameraList.end()) {
                    LOG(INFO) << deviceName << " has been added already.";
                    captureCount++;
                } else if(qualifyCaptureDevice(deviceName.c_str())) {
                    sCameraList.emplace(deviceName, deviceName.c_str());
                    captureCount++;
                }
            }
        }
    }

    LOG(INFO) << "Found " << captureCount << " qualified video capture devices "
              << "of " << videoCount << " checked.";
}


void EvsEnumerator::enumerateDisplays() {
    LOG(INFO) << __FUNCTION__
              << ": Starting display enumeration";
    if (!sDisplayProxy) {
        LOG(ERROR) << "AutomotiveDisplayProxyService is not available!";
        return;
    }

    sDisplayProxy->getDisplayIdList(
        [](const auto& displayIds) {
            // The first entry of the list is the internal display.  See
            // SurfaceFlinger::getPhysicalDisplayIds() implementation.
            if (displayIds.size() > 0) {
                sInternalDisplayId = displayIds[0];
                for (const auto& id : displayIds) {
                    const auto port = id & 0xFF;
                    LOG(INFO) << "Display " << std::hex << id
                              << " is detected on the port, " << port;
                    sDisplayPortList.insert_or_assign(port, id);
                }
            }
        }
    );

    LOG(INFO) << "Found " << sDisplayPortList.size() << " displays";
}


// Methods from ::android::hardware::automotive::evs::V1_0::IEvsEnumerator follow.
Return<void> EvsEnumerator::getCameraList(getCameraList_cb _hidl_cb)  {
    LOG(DEBUG) << __FUNCTION__;
    if (!checkPermission()) {
        return Void();
    }

    {
        std::unique_lock<std::mutex> lock(sLock);
        if (sCameraList.size() < 1) {
            // No qualified device has been found.  Wait until new device is ready,
            // for 10 seconds.
            if (!sCameraSignal.wait_for(lock,
                                        kEnumerationTimeout,
                                        []{ return sCameraList.size() > 0; })) {
                LOG(DEBUG) << "Timer expired.  No new device has been added.";
            }
        }
    }

    const unsigned numCameras = sCameraList.size();

    // Build up a packed array of CameraDesc for return
    hidl_vec<CameraDesc_1_0> hidlCameras;
    hidlCameras.resize(numCameras);
    unsigned i = 0;
    for (const auto& [key, cam] : sCameraList) {
        hidlCameras[i++] = cam.desc.v1;
    }

    // Send back the results
    LOG(DEBUG) << "Reporting " << hidlCameras.size() << " cameras available";
    _hidl_cb(hidlCameras);

    // HIDL convention says we return Void if we sent our result back via callback
    return Void();
}


Return<sp<IEvsCamera_1_0>> EvsEnumerator::openCamera(const hidl_string& cameraId) {
    LOG(DEBUG) << __FUNCTION__;
    if (!checkPermission()) {
        return nullptr;
    }

    // Is this a recognized camera id?
    CameraRecord *pRecord = findCameraById(cameraId);
    if (pRecord == nullptr) {
        LOG(ERROR) << cameraId << " does not exist!";
        return nullptr;
    }

    // Has this camera already been instantiated by another caller?
    sp<EvsV4lCamera> pActiveCamera = pRecord->activeInstance.promote();
    if (pActiveCamera != nullptr) {
        LOG(WARNING) << "Killing previous camera because of new caller";
        closeCamera(pActiveCamera);
    }

    // Construct a camera instance for the caller
    if (sConfigManager == nullptr) {
        pActiveCamera = EvsV4lCamera::Create(cameraId.c_str());
    } else {
        pActiveCamera = EvsV4lCamera::Create(cameraId.c_str(),
                                             sConfigManager->getCameraInfo(cameraId));
    }

    pRecord->activeInstance = pActiveCamera;
    if (pActiveCamera == nullptr) {
        LOG(ERROR) << "Failed to create new EvsV4lCamera object for " << cameraId;
    }

    return pActiveCamera;
}


Return<void> EvsEnumerator::closeCamera(const ::android::sp<IEvsCamera_1_0>& pCamera) {
    LOG(DEBUG) << __FUNCTION__;

    if (pCamera == nullptr) {
        LOG(ERROR) << "Ignoring call to closeCamera with null camera ptr";
        return Void();
    }

    // Get the camera id so we can find it in our list
    std::string cameraId;
    pCamera->getCameraInfo([&cameraId](CameraDesc_1_0 desc) {
                               cameraId = desc.cameraId;
                           }
    );

    closeCamera_impl(pCamera, cameraId);

    return Void();
}


Return<sp<IEvsDisplay_1_0>> EvsEnumerator::openDisplay() {
    LOG(DEBUG) << __FUNCTION__;
    if (!checkPermission()) {
        return nullptr;
    }

    // If we already have a display active, then we need to shut it down so we can
    // give exclusive access to the new caller.
    sp<EvsGlDisplay> pActiveDisplay = sActiveDisplay.promote();
    if (pActiveDisplay != nullptr) {
        LOG(WARNING) << "Killing previous display because of new caller";
        closeDisplay(pActiveDisplay);
    }

    // Create a new display interface and return it.
    pActiveDisplay = new EvsGlDisplay(sDisplayProxy, sInternalDisplayId);
    sActiveDisplay = pActiveDisplay;

    LOG(DEBUG) << "Returning new EvsGlDisplay object " << pActiveDisplay.get();
    return pActiveDisplay;
}


Return<void> EvsEnumerator::closeDisplay(const ::android::sp<IEvsDisplay_1_0>& pDisplay) {
    LOG(DEBUG) << __FUNCTION__;

    // Do we still have a display object we think should be active?
    sp<EvsGlDisplay> pActiveDisplay = sActiveDisplay.promote();
    if (pActiveDisplay == nullptr) {
        LOG(ERROR) << "Somehow a display is being destroyed "
                   << "when the enumerator didn't know one existed";
    } else if (sActiveDisplay != pDisplay) {
        LOG(WARNING) << "Ignoring close of previously orphaned display - why did a client steal?";
    } else {
        // Drop the active display
        pActiveDisplay->forceShutdown();
        sActiveDisplay = nullptr;
    }

    return Void();
}


Return<EvsDisplayState> EvsEnumerator::getDisplayState()  {
    LOG(DEBUG) << __FUNCTION__;
    if (!checkPermission()) {
        return EvsDisplayState::DEAD;
    }

    // Do we still have a display object we think should be active?
    sp<IEvsDisplay_1_0> pActiveDisplay = sActiveDisplay.promote();
    if (pActiveDisplay != nullptr) {
        return pActiveDisplay->getDisplayState();
    } else {
        return EvsDisplayState::NOT_OPEN;
    }
}


// Methods from ::android::hardware::automotive::evs::V1_1::IEvsEnumerator follow.
Return<void> EvsEnumerator::getCameraList_1_1(getCameraList_1_1_cb _hidl_cb)  {
    LOG(DEBUG) << __FUNCTION__;
    if (!checkPermission()) {
        return Void();
    }

    {
        std::unique_lock<std::mutex> lock(sLock);
        if (sCameraList.size() < 1) {
            // No qualified device has been found.  Wait until new device is ready,
            if (!sCameraSignal.wait_for(lock,
                                        kEnumerationTimeout,
                                        []{ return sCameraList.size() > 0; })) {
                LOG(DEBUG) << "Timer expired.  No new device has been added.";
            }
        }
    }

    std::vector<CameraDesc_1_1> hidlCameras;
    if (sConfigManager == nullptr) {
        auto numCameras = sCameraList.size();

        // Build up a packed array of CameraDesc for return
        hidlCameras.resize(numCameras);
        unsigned i = 0;
        for (auto&& [key, cam] : sCameraList) {
            hidlCameras[i++] = cam.desc;
        }
    } else {
        // Build up a packed array of CameraDesc for return
        for (auto&& [key, cam] : sCameraList) {
            unique_ptr<ConfigManager::CameraInfo> &tempInfo =
                sConfigManager->getCameraInfo(key);
            if (tempInfo != nullptr) {
                cam.desc.metadata.setToExternal(
                    (uint8_t *)tempInfo->characteristics,
                     get_camera_metadata_size(tempInfo->characteristics)
                );
            }

            hidlCameras.emplace_back(cam.desc);
        }

        // Adding camera groups that represent logical camera devices
        auto camGroups = sConfigManager->getCameraGroupIdList();
        for (auto&& id : camGroups) {
            if (sCameraList.find(id) != sCameraList.end()) {
                // Already exists in the list
                continue;
            }

            unique_ptr<ConfigManager::CameraGroupInfo> &tempInfo =
                sConfigManager->getCameraGroupInfo(id);
            CameraRecord cam(id.c_str());
            if (tempInfo != nullptr) {
                cam.desc.metadata.setToExternal(
                    (uint8_t *)tempInfo->characteristics,
                     get_camera_metadata_size(tempInfo->characteristics)
                );
            }

            sCameraList.emplace(id, cam);
            hidlCameras.emplace_back(cam.desc);
        }
    }

    // Send back the results
    _hidl_cb(hidlCameras);

    // HIDL convention says we return Void if we sent our result back via callback
    return Void();
}


Return<sp<IEvsCamera_1_1>> EvsEnumerator::openCamera_1_1(const hidl_string& cameraId,
                                                         const Stream& streamCfg) {
    LOG(DEBUG) << __FUNCTION__;
    if (!checkPermission()) {
        return nullptr;
    }

    // Is this a recognized camera id?
    CameraRecord *pRecord = findCameraById(cameraId);
    if (pRecord == nullptr) {
        LOG(ERROR) << cameraId << " does not exist!";
        return nullptr;
    }

    // Has this camera already been instantiated by another caller?
    sp<EvsV4lCamera> pActiveCamera = pRecord->activeInstance.promote();
    if (pActiveCamera != nullptr) {
        LOG(WARNING) << "Killing previous camera because of new caller";
        closeCamera(pActiveCamera);
    }

    // Construct a camera instance for the caller
    if (sConfigManager == nullptr) {
        LOG(WARNING) << "ConfigManager is not available.  "
                     << "Given stream configuration is ignored.";
        pActiveCamera = EvsV4lCamera::Create(cameraId.c_str());
    } else {
        pActiveCamera = EvsV4lCamera::Create(cameraId.c_str(),
                                             sConfigManager->getCameraInfo(cameraId),
                                             &streamCfg);
    }
    pRecord->activeInstance = pActiveCamera;
    if (pActiveCamera == nullptr) {
        LOG(ERROR) << "Failed to create new EvsV4lCamera object for " << cameraId;
    }

    return pActiveCamera;
}


Return<void> EvsEnumerator::getDisplayIdList(getDisplayIdList_cb _list_cb) {
    hidl_vec<uint8_t> ids;

    if (sDisplayPortList.size() > 0) {
        ids.resize(sDisplayPortList.size());
        unsigned i = 0;
        ids[i++] = sInternalDisplayId & 0xFF;
        for (const auto& [port, id] : sDisplayPortList) {
            if (sInternalDisplayId != id) {
                ids[i++] = port;
            }
        }
    }

    _list_cb(ids);
    return Void();
}


Return<sp<IEvsDisplay_1_1>> EvsEnumerator::openDisplay_1_1(uint8_t port) {
    LOG(DEBUG) << __FUNCTION__;
    if (!checkPermission()) {
        return nullptr;
    }

    // If we already have a display active, then we need to shut it down so we can
    // give exclusive access to the new caller.
    sp<EvsGlDisplay> pActiveDisplay = sActiveDisplay.promote();
    if (pActiveDisplay != nullptr) {
        LOG(WARNING) << "Killing previous display because of new caller";
        closeDisplay(pActiveDisplay);
    }

    // Create a new display interface and return it
    if (sDisplayPortList.find(port) == sDisplayPortList.end()) {
        LOG(ERROR) << "No display is available on the port "
                   << static_cast<int32_t>(port);
        return nullptr;
    }

    pActiveDisplay = new EvsGlDisplay(sDisplayProxy, sDisplayPortList[port]);
    sActiveDisplay = pActiveDisplay;

    LOG(DEBUG) << "Returning new EvsGlDisplay object " << pActiveDisplay.get();
    return pActiveDisplay;
}


void EvsEnumerator::closeCamera_impl(const sp<IEvsCamera_1_0>& pCamera,
                                     const std::string& cameraId) {
    // Find the named camera
    CameraRecord *pRecord = findCameraById(cameraId);

    // Is the display being destroyed actually the one we think is active?
    if (!pRecord) {
        LOG(ERROR) << "Asked to close a camera whose name isn't recognized";
    } else {
        sp<EvsV4lCamera> pActiveCamera = pRecord->activeInstance.promote();

        if (pActiveCamera == nullptr) {
            LOG(ERROR) << "Somehow a camera is being destroyed "
                       << "when the enumerator didn't know one existed";
        } else if (pActiveCamera != pCamera) {
            // This can happen if the camera was aggressively reopened,
            // orphaning this previous instance
            LOG(WARNING) << "Ignoring close of previously orphaned camera "
                         << "- why did a client steal?";
        } else {
            // Drop the active camera
            pActiveCamera->shutdown();
            pRecord->activeInstance = nullptr;
        }
    }

    return;
}


bool EvsEnumerator::qualifyCaptureDevice(const char* deviceName) {
    class FileHandleWrapper {
    public:
        FileHandleWrapper(int fd)   { mFd = fd; }
        ~FileHandleWrapper()        { if (mFd > 0) close(mFd); }
        operator int() const        { return mFd; }
    private:
        int mFd = -1;
    };


    FileHandleWrapper fd = open(deviceName, O_RDWR, 0);
    if (fd < 0) {
        return false;
    }

    v4l2_capability caps;
    int result = ioctl(fd, VIDIOC_QUERYCAP, &caps);
    if (result  < 0) {
        return false;
    }
    if (((caps.capabilities & V4L2_CAP_VIDEO_CAPTURE) == 0) ||
        ((caps.capabilities & V4L2_CAP_STREAMING)     == 0)) {
        return false;
    }

    // Enumerate the available capture formats (if any)
    v4l2_fmtdesc formatDescription;
    formatDescription.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
    bool found = false;
    for (int i=0; !found; i++) {
        formatDescription.index = i;
        if (ioctl(fd, VIDIOC_ENUM_FMT, &formatDescription) == 0) {
            LOG(INFO) << "Format: 0x" << std::hex << formatDescription.pixelformat
                      << " Type: 0x" << std::hex << formatDescription.type
                      << " Desc: " << formatDescription.description
                      << " Flags: 0x" << std::hex << formatDescription.flags;
            switch (formatDescription.pixelformat)
            {
                case V4L2_PIX_FMT_YUYV:     found = true; break;
                case V4L2_PIX_FMT_NV21:     found = true; break;
                case V4L2_PIX_FMT_NV16:     found = true; break;
                case V4L2_PIX_FMT_YVU420:   found = true; break;
                case V4L2_PIX_FMT_RGB32:    found = true; break;
#ifdef V4L2_PIX_FMT_ARGB32  // introduced with kernel v3.17
                case V4L2_PIX_FMT_ARGB32:   found = true; break;
                case V4L2_PIX_FMT_XRGB32:   found = true; break;
#endif // V4L2_PIX_FMT_ARGB32
                default:
                    LOG(WARNING) << "Unsupported, "
                                 << std::hex << formatDescription.pixelformat;
                    break;
            }
        } else {
            // No more formats available.
            break;
        }
    }

    return found;
}


EvsEnumerator::CameraRecord* EvsEnumerator::findCameraById(const std::string& cameraId) {
    // Find the named camera
    auto found = sCameraList.find(cameraId);
    if (sCameraList.end() != found) {
        // Found a match!
        return &found->second;
    }

    // We didn't find a match
    return nullptr;
}


// TODO(b/149874793): Add implementation for EVS Manager and Sample driver
Return<void> EvsEnumerator::getUltrasonicsArrayList(getUltrasonicsArrayList_cb _hidl_cb) {
    hidl_vec<UltrasonicsArrayDesc> ultrasonicsArrayDesc;
    _hidl_cb(ultrasonicsArrayDesc);
    return Void();
}


// TODO(b/149874793): Add implementation for EVS Manager and Sample driver
Return<sp<IEvsUltrasonicsArray>> EvsEnumerator::openUltrasonicsArray(
        const hidl_string& ultrasonicsArrayId) {
    (void)ultrasonicsArrayId;
    return sp<IEvsUltrasonicsArray>();
}


// TODO(b/149874793): Add implementation for EVS Manager and Sample driver
Return<void> EvsEnumerator::closeUltrasonicsArray(
        const ::android::sp<IEvsUltrasonicsArray>& evsUltrasonicsArray)  {
    (void)evsUltrasonicsArray;
    return Void();
}


using android::base::Result;
using android::base::EqualsIgnoreCase;
using android::base::StringPrintf;
using android::base::WriteStringToFd;
Return<void> EvsEnumerator::debug(const hidl_handle& fd,
                                  const hidl_vec<hidl_string>& options) {
    if (fd.getNativeHandle() != nullptr && fd->numFds > 0) {
        parseCommand(fd->data[0], options);
    } else {
        LOG(ERROR) << "Given file descriptor is not valid.";
    }

    return {};
}


void EvsEnumerator::parseCommand(int fd, const hidl_vec<hidl_string>& options) {
    if (options.size() < 1) {
        WriteStringToFd("No option is given.\n", fd);
        cmdHelp(fd);
        return;
    }

    const std::string command = options[0];
    if (EqualsIgnoreCase(command, "--help")) {
        cmdHelp(fd);
    } else if (EqualsIgnoreCase(command, "--dump")) {
        cmdDump(fd, options);
    } else {
        WriteStringToFd(StringPrintf("Invalid option: %s\n", command.c_str()), fd);
    }
}


void EvsEnumerator::cmdHelp(int fd) {
    WriteStringToFd("--help: shows this help.\n"
                    "--dump [id] [start|stop] [directory]\n"
                    "\tDump camera frames to a target directory\n", fd);
}


void EvsEnumerator::cmdDump(int fd, const hidl_vec<hidl_string>& options) {
    if (options.size() < 3) {
        WriteStringToFd("Necessary argument is missing\n", fd);
        cmdHelp(fd);
        return;
    }

    EvsEnumerator::CameraRecord *pRecord = findCameraById(options[1]);
    if (pRecord == nullptr) {
        WriteStringToFd(StringPrintf("%s is not active\n", options[1].c_str()), fd);
        return;
    }

    auto device = pRecord->activeInstance.promote();
    if (device == nullptr) {
        WriteStringToFd(StringPrintf("%s seems dead\n", options[1].c_str()), fd);
        return;
    }

    const std::string command = options[2];
    if (EqualsIgnoreCase(command, "start")) {
        // --dump [device id] start [path]
        if (options.size() < 4) {
            WriteStringToFd("Necessary argument is missing\n", fd);
            cmdHelp(fd);
            return;
        }

        const std::string path = options[3];
        auto ret = device->startDumpFrames(path);
        if (!ret.ok()) {
            WriteStringToFd(StringPrintf("Failed to start storing frames: %s\n",
                                         ret.error().message().c_str()), fd);
        }
    } else if (EqualsIgnoreCase(command, "stop")) {
        // --dump [device id] stop
        auto ret = device->stopDumpFrames();
        if (!ret.ok()) {
            WriteStringToFd(StringPrintf("Failed to stop storing frames: %s\n",
                                         ret.error().message().c_str()), fd);
        }
    } else {
        WriteStringToFd(StringPrintf("Unknown command: %s", command.c_str()), fd);
        cmdHelp(fd);
    }

    return;
}


} // namespace implementation
} // namespace V1_1
} // namespace evs
} // namespace automotive
} // namespace hardware
} // namespace android