path: root/usb/Usb.cpp

/*
 * Copyright (C) 2020 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.
 */

#define LOG_TAG "android.hardware.usb@1.3-service.crosshatch"

#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/parseint.h>
#include <android-base/strings.h>
#include <assert.h>
#include <dirent.h>
#include <pthread.h>
#include <stdio.h>
#include <sys/types.h>
#include <unistd.h>
#include <chrono>
#include <regex>
#include <thread>
#include <unordered_map>

#include <cutils/uevent.h>
#include <sys/epoll.h>
#include <utils/Errors.h>
#include <utils/StrongPointer.h>

#include "Usb.h"

namespace android {
namespace hardware {
namespace usb {
namespace V1_3 {
namespace implementation {

Return<bool> Usb::enableUsbDataSignal(bool enable) {
    bool result = true;

    ALOGI("Userspace turn %s USB data signaling", enable ? "on" : "off");

    if (enable) {
        if (!WriteStringToFile("1", USB_DATA_PATH)) {
            ALOGE("Not able to turn on usb connection notification");
            result = false;
        }

        if (!WriteStringToFile(kGadgetName, PULLUP_PATH)) {
            ALOGE("Gadget cannot be pulled up");
            result = false;
        }
    } else {
        if (!WriteStringToFile("1", ID_PATH)) {
            ALOGE("Not able to turn off host mode");
            result = false;
        }

        if (!WriteStringToFile("0", VBUS_PATH)) {
            ALOGE("Not able to set Vbus state");
            result = false;
        }

        if (!WriteStringToFile("0", USB_DATA_PATH)) {
            ALOGE("Not able to turn on usb connection notification");
            result = false;
        }

        if (!WriteStringToFile("none", PULLUP_PATH)) {
            ALOGE("Gadget cannot be pulled down");
            result = false;
        }
    }

    return result;
}

// Set by the signal handler to destroy the thread
volatile bool destroyThread;

int32_t readFile(const std::string &filename, std::string *contents) {
  FILE *fp;
  ssize_t read = 0;
  char *line = NULL;
  size_t len = 0;

  fp = fopen(filename.c_str(), "r");
  if (fp != NULL) {
    if ((read = getline(&line, &len, fp)) != -1) {
      char *pos;
      if ((pos = strchr(line, '\n')) != NULL) *pos = '\0';
      *contents = line;
    }
    free(line);
    fclose(fp);
    return 0;
  } else {
    ALOGE("fopen failed");
  }

  return -1;
}

Status queryMoistureDetectionStatus(hidl_vec<PortStatus> *currentPortStatus_1_2) {
  std::string enabled, status, path, DetectedPath;

  if (currentPortStatus_1_2 == NULL || currentPortStatus_1_2->size() == 0) {
      ALOGE("currentPortStatus_1_2 is not available");
      return Status::ERROR;
  }

  (*currentPortStatus_1_2)[0].supportedContaminantProtectionModes = 0;
  (*currentPortStatus_1_2)[0].supportedContaminantProtectionModes |=
      V1_2::ContaminantProtectionMode::FORCE_SINK;
  (*currentPortStatus_1_2)[0].contaminantProtectionStatus =
      V1_2::ContaminantProtectionStatus::NONE;
  (*currentPortStatus_1_2)[0].contaminantDetectionStatus =
      V1_2::ContaminantDetectionStatus::NOT_DETECTED;
  (*currentPortStatus_1_2)[0].supportsEnableContaminantPresenceDetection = false;
  (*currentPortStatus_1_2)[0].supportsEnableContaminantPresenceProtection = false;

  ALOGI("ContaminantDetectionStatus:%d ContaminantProtectionStatus:%d",
        (*currentPortStatus_1_2)[0].contaminantDetectionStatus,
        (*currentPortStatus_1_2)[0].contaminantProtectionStatus);

  return Status::SUCCESS;
}

std::string appendRoleNodeHelper(const std::string &portName,
                                 PortRoleType type) {
  std::string node("/sys/class/typec/" + portName);

  switch (type) {
    case PortRoleType::DATA_ROLE:
      return node + "/data_role";
    case PortRoleType::POWER_ROLE:
      return node + "/power_role";
    case PortRoleType::MODE:
      return node + "/port_type";
    default:
      return "";
  }
}

std::string convertRoletoString(PortRole role) {
  if (role.type == PortRoleType::POWER_ROLE) {
    if (role.role == static_cast<uint32_t>(PortPowerRole::SOURCE))
      return "source";
    else if (role.role == static_cast<uint32_t>(PortPowerRole::SINK))
      return "sink";
  } else if (role.type == PortRoleType::DATA_ROLE) {
    if (role.role == static_cast<uint32_t>(PortDataRole::HOST)) return "host";
    if (role.role == static_cast<uint32_t>(PortDataRole::DEVICE))
          return "device";
  } else if (role.type == PortRoleType::MODE) {
    if (role.role == static_cast<uint32_t>(PortMode_1_1::UFP)) return "sink";
    if (role.role == static_cast<uint32_t>(PortMode_1_1::DFP)) return "source";
  }
  return "none";
}

void extractRole(std::string *roleName) {
  std::size_t first, last;

  first = roleName->find("[");
  last = roleName->find("]");

  if (first != std::string::npos && last != std::string::npos) {
    *roleName = roleName->substr(first + 1, last - first - 1);
  }
}

void switchToDrp(const std::string &portName) {
  std::string filename =
      appendRoleNodeHelper(std::string(portName.c_str()), PortRoleType::MODE);
  FILE *fp;

  if (filename != "") {
    fp = fopen(filename.c_str(), "w");
    if (fp != NULL) {
      int ret = fputs("dual", fp);
      fclose(fp);
      if (ret == EOF)
        ALOGE("Fatal: Error while switching back to drp");
    } else {
      ALOGE("Fatal: Cannot open file to switch back to drp");
    }
  } else {
    ALOGE("Fatal: invalid node type");
  }
}

bool switchMode(const hidl_string &portName,
                             const PortRole &newRole, struct Usb *usb) {
  std::string filename =
       appendRoleNodeHelper(std::string(portName.c_str()), newRole.type);
  std::string written;
  FILE *fp;
  bool roleSwitch = false;

  if (filename == "") {
    ALOGE("Fatal: invalid node type");
    return false;
  }

  fp = fopen(filename.c_str(), "w");
  if (fp != NULL) {
    // Hold the lock here to prevent loosing connected signals
    // as once the file is written the partner added signal
    // can arrive anytime.
    pthread_mutex_lock(&usb->mPartnerLock);
    usb->mPartnerUp = false;
    int ret = fputs(convertRoletoString(newRole).c_str(), fp);
    fclose(fp);

    if (ret != EOF) {
      struct timespec   to;
      struct timespec   now;

wait_again:
      clock_gettime(CLOCK_MONOTONIC, &now);
      to.tv_sec = now.tv_sec + PORT_TYPE_TIMEOUT;
      to.tv_nsec = now.tv_nsec;

      int err = pthread_cond_timedwait(&usb->mPartnerCV, &usb->mPartnerLock, &to);
      // There are no uevent signals which implies role swap timed out.
      if (err == ETIMEDOUT) {
        ALOGI("uevents wait timedout");
      // Partner check.
      } else if (!usb->mPartnerUp) {
        goto wait_again;
      // Role switch succeeded since usb->mPartnerUp is true.
      } else {
        roleSwitch = true;
      }
    } else {
      ALOGI("Role switch failed while wrting to file");
    }
    pthread_mutex_unlock(&usb->mPartnerLock);
  }

  if (!roleSwitch)
    switchToDrp(std::string(portName.c_str()));

  return roleSwitch;
}

Usb::Usb()
        : mLock(PTHREAD_MUTEX_INITIALIZER),
          mRoleSwitchLock(PTHREAD_MUTEX_INITIALIZER),
          mPartnerLock(PTHREAD_MUTEX_INITIALIZER),
          mPartnerUp(false) {
    pthread_condattr_t attr;
    if (pthread_condattr_init(&attr)) {
        ALOGE("pthread_condattr_init failed: %s", strerror(errno));
        abort();
    }
    if (pthread_condattr_setclock(&attr, CLOCK_MONOTONIC)) {
        ALOGE("pthread_condattr_setclock failed: %s", strerror(errno));
        abort();
    }
    if (pthread_cond_init(&mPartnerCV, &attr))  {
        ALOGE("pthread_cond_init failed: %s", strerror(errno));
        abort();
    }
    if (pthread_condattr_destroy(&attr)) {
        ALOGE("pthread_condattr_destroy failed: %s", strerror(errno));
        abort();
    }
}


Return<void> Usb::switchRole(const hidl_string &portName,
                             const V1_0::PortRole &newRole) {
  std::string filename =
      appendRoleNodeHelper(std::string(portName.c_str()), newRole.type);
  std::string written;
  FILE *fp;
  bool roleSwitch = false;

  if (filename == "") {
    ALOGE("Fatal: invalid node type");
    return Void();
  }

  pthread_mutex_lock(&mRoleSwitchLock);

  ALOGI("filename write: %s role:%s", filename.c_str(),
        convertRoletoString(newRole).c_str());

  if (newRole.type == PortRoleType::MODE) {
      roleSwitch = switchMode(portName, newRole, this);
  } else {
    fp = fopen(filename.c_str(), "w");
    if (fp != NULL) {
      int ret = fputs(convertRoletoString(newRole).c_str(), fp);
      fclose(fp);
      if ((ret != EOF) && !readFile(filename, &written)) {
        extractRole(&written);
        ALOGI("written: %s", written.c_str());
        if (written == convertRoletoString(newRole)) {
          roleSwitch = true;
        } else {
          ALOGE("Role switch failed");
        }
      } else {
        ALOGE("failed to update the new role");
      }
    } else {
      ALOGE("fopen failed");
    }
  }

  pthread_mutex_lock(&mLock);
  if (mCallback_1_0 != NULL) {
    Return<void> ret =
        mCallback_1_0->notifyRoleSwitchStatus(portName, newRole,
        roleSwitch ? Status::SUCCESS : Status::ERROR);
    if (!ret.isOk())
      ALOGE("RoleSwitchStatus error %s", ret.description().c_str());
  } else {
    ALOGE("Not notifying the userspace. Callback is not set");
  }
  pthread_mutex_unlock(&mLock);
  pthread_mutex_unlock(&mRoleSwitchLock);

  return Void();
}

Status getAccessoryConnected(const std::string &portName, std::string *accessory) {
  std::string filename =
    "/sys/class/typec/" + portName + "-partner/accessory_mode";

  if (readFile(filename, accessory)) {
    ALOGE("getAccessoryConnected: Failed to open filesystem node: %s",
          filename.c_str());
    return Status::ERROR;
  }

  return Status::SUCCESS;
}

Status getCurrentRoleHelper(const std::string &portName, bool connected,
                            PortRoleType type, uint32_t *currentRole) {
  std::string filename;
  std::string roleName;
  std::string accessory;

  // Mode

  if (type == PortRoleType::POWER_ROLE) {
    filename = "/sys/class/typec/" + portName + "/power_role";
    *currentRole = static_cast<uint32_t>(PortPowerRole::NONE);
  } else if (type == PortRoleType::DATA_ROLE) {
    filename = "/sys/class/typec/" + portName + "/data_role";
    *currentRole = static_cast<uint32_t>(PortDataRole::NONE);
  } else if (type == PortRoleType::MODE) {
    filename = "/sys/class/typec/" + portName + "/data_role";
    *currentRole = static_cast<uint32_t>(PortMode_1_1::NONE);
  } else {
    return Status::ERROR;
  }

  if (!connected) return Status::SUCCESS;

  if (type == PortRoleType::MODE) {
    if (getAccessoryConnected(portName, &accessory) != Status::SUCCESS) {
      return Status::ERROR;
    }
    if (accessory == "analog_audio") {
      *currentRole = static_cast<uint32_t>(PortMode_1_1::AUDIO_ACCESSORY);
      return Status::SUCCESS;
    } else if (accessory == "debug") {
      *currentRole = static_cast<uint32_t>(PortMode_1_1::DEBUG_ACCESSORY);
      return Status::SUCCESS;
    }
  }

  if (readFile(filename, &roleName)) {
    ALOGE("getCurrentRole: Failed to open filesystem node: %s",
          filename.c_str());
    return Status::ERROR;
  }

  extractRole(&roleName);

  if (roleName == "source") {
    *currentRole = static_cast<uint32_t>(PortPowerRole::SOURCE);
  } else if (roleName == "sink") {
    *currentRole = static_cast<uint32_t>(PortPowerRole::SINK);
  } else if (roleName == "host") {
    if (type == PortRoleType::DATA_ROLE)
      *currentRole = static_cast<uint32_t>(PortDataRole::HOST);
    else
      *currentRole = static_cast<uint32_t>(PortMode_1_1::DFP);
  } else if (roleName == "device") {
    if (type == PortRoleType::DATA_ROLE)
      *currentRole = static_cast<uint32_t>(PortDataRole::DEVICE);
    else
      *currentRole = static_cast<uint32_t>(PortMode_1_1::UFP);
  } else if (roleName != "none") {
    /* case for none has already been addressed.
     * so we check if the role isnt none.
     */
    return Status::UNRECOGNIZED_ROLE;
  }

  return Status::SUCCESS;
}

Status getTypeCPortNamesHelper(std::unordered_map<std::string, bool> *names) {
  DIR *dp;

  dp = opendir("/sys/class/typec");
  if (dp != NULL) {
    struct dirent *ep;

    while ((ep = readdir(dp))) {
      if (ep->d_type == DT_LNK) {
        if (std::string::npos == std::string(ep->d_name).find("-partner")) {
          std::unordered_map<std::string, bool>::const_iterator portName =
              names->find(ep->d_name);
          if (portName == names->end()) {
            names->insert({ep->d_name, false});
          }
        } else {
          (*names)[std::strtok(ep->d_name, "-")] = true;
        }
      }
    }
    closedir(dp);
    return Status::SUCCESS;
  }

  ALOGE("Failed to open /sys/class/typec");
  return Status::ERROR;
}

bool canSwitchRoleHelper(const std::string &portName, PortRoleType /*type*/) {
  std::string filename =
      "/sys/class/typec/" + portName + "-partner/supports_usb_power_delivery";
  std::string supportsPD;

  if (!readFile(filename, &supportsPD)) {
    if (supportsPD == "yes") {
      return true;
    }
  }

  return false;
}

/*
 * Reuse the same method for both V1_0 and V1_1 callback objects.
 * The caller of this method would reconstruct the V1_0::PortStatus
 * object if required.
 */
Status getPortStatusHelper(hidl_vec<PortStatus> *currentPortStatus_1_2, HALVersion version) {
    std::unordered_map<std::string, bool> names;
    Status result = getTypeCPortNamesHelper(&names);
    int i = -1;

    if (result == Status::SUCCESS) {
        currentPortStatus_1_2->resize(names.size());
        for (std::pair<std::string, bool> port : names) {
            i++;
            ALOGI("%s", port.first.c_str());
            (*currentPortStatus_1_2)[i].status_1_1.status.portName = port.first;

            uint32_t currentRole;
            if (getCurrentRoleHelper(port.first, port.second, PortRoleType::POWER_ROLE,
                                     &currentRole) == Status::SUCCESS) {
                (*currentPortStatus_1_2)[i].status_1_1.status.currentPowerRole =
                    static_cast<PortPowerRole>(currentRole);
            } else {
                ALOGE("Error while retrieving portNames");
                goto done;
            }

            if (getCurrentRoleHelper(port.first, port.second, PortRoleType::DATA_ROLE,
                                     &currentRole) == Status::SUCCESS) {
                (*currentPortStatus_1_2)[i].status_1_1.status.currentDataRole =
                    static_cast<PortDataRole>(currentRole);
            } else {
                ALOGE("Error while retrieving current port role");
                goto done;
            }

            if (getCurrentRoleHelper(port.first, port.second, PortRoleType::MODE, &currentRole) ==
                Status::SUCCESS) {
                (*currentPortStatus_1_2)[i].status_1_1.currentMode =
                    static_cast<PortMode_1_1>(currentRole);
                (*currentPortStatus_1_2)[i].status_1_1.status.currentMode =
                    static_cast<V1_0::PortMode>(currentRole);
            } else {
                ALOGE("Error while retrieving current data role");
                goto done;
            }

            (*currentPortStatus_1_2)[i].status_1_1.status.canChangeMode = true;
            (*currentPortStatus_1_2)[i].status_1_1.status.canChangeDataRole =
                port.second ? canSwitchRoleHelper(port.first, PortRoleType::DATA_ROLE) : false;
            (*currentPortStatus_1_2)[i].status_1_1.status.canChangePowerRole =
                port.second ? canSwitchRoleHelper(port.first, PortRoleType::POWER_ROLE) : false;

            if (version == HALVersion::V1_0) {
                ALOGI("HAL version V1_0");
                (*currentPortStatus_1_2)[i].status_1_1.status.supportedModes = V1_0::PortMode::DRP;
            } else {
                if (version == HALVersion::V1_1)
                    ALOGI("HAL version V1_1");
                else
                    ALOGI("HAL version V1_2");
                (*currentPortStatus_1_2)[i].status_1_1.supportedModes = 0 | PortMode_1_1::DRP;
                (*currentPortStatus_1_2)[i].status_1_1.status.supportedModes = V1_0::PortMode::NONE;
                (*currentPortStatus_1_2)[i].status_1_1.status.currentMode = V1_0::PortMode::NONE;
            }

            ALOGI(
                "%d:%s connected:%d canChangeMode:%d canChagedata:%d canChangePower:%d "
                "supportedModes:%d",
                i, port.first.c_str(), port.second,
                (*currentPortStatus_1_2)[i].status_1_1.status.canChangeMode,
                (*currentPortStatus_1_2)[i].status_1_1.status.canChangeDataRole,
                (*currentPortStatus_1_2)[i].status_1_1.status.canChangePowerRole,
                (*currentPortStatus_1_2)[i].status_1_1.supportedModes);
        }
        return Status::SUCCESS;
    }
done:
    return Status::ERROR;
}

void queryVersionHelper(android::hardware::usb::V1_3::implementation::Usb *usb,
                        hidl_vec<PortStatus> *currentPortStatus_1_2) {
    hidl_vec<V1_1::PortStatus_1_1> currentPortStatus_1_1;
    hidl_vec<V1_0::PortStatus> currentPortStatus;
    Status status;
    sp<V1_1::IUsbCallback> callback_V1_1 = V1_1::IUsbCallback::castFrom(usb->mCallback_1_0);
    sp<IUsbCallback> callback_V1_2 = IUsbCallback::castFrom(usb->mCallback_1_0);

    pthread_mutex_lock(&usb->mLock);
    if (usb->mCallback_1_0 != NULL) {
        if (callback_V1_2 != NULL) {
            status = getPortStatusHelper(currentPortStatus_1_2, HALVersion::V1_2);
            if (status == Status::SUCCESS)
                queryMoistureDetectionStatus(currentPortStatus_1_2);
        } else if (callback_V1_1 != NULL) {
            status = getPortStatusHelper(currentPortStatus_1_2, HALVersion::V1_1);
            currentPortStatus_1_1.resize(currentPortStatus_1_2->size());
            for (unsigned long i = 0; i < currentPortStatus_1_2->size(); i++)
                currentPortStatus_1_1[i] = (*currentPortStatus_1_2)[i].status_1_1;
        } else {
            status = getPortStatusHelper(currentPortStatus_1_2, HALVersion::V1_0);
            currentPortStatus.resize(currentPortStatus_1_2->size());
            for (unsigned long i = 0; i < currentPortStatus_1_2->size(); i++)
                currentPortStatus[i] = (*currentPortStatus_1_2)[i].status_1_1.status;
        }

        Return<void> ret;

        if (callback_V1_2 != NULL)
            ret = callback_V1_2->notifyPortStatusChange_1_2(*currentPortStatus_1_2, status);
        else if (callback_V1_1 != NULL)
            ret = callback_V1_1->notifyPortStatusChange_1_1(currentPortStatus_1_1, status);
        else
            ret = usb->mCallback_1_0->notifyPortStatusChange(currentPortStatus, status);

        if (!ret.isOk())
            ALOGE("queryPortStatus_1_2 error %s", ret.description().c_str());
    } else {
        ALOGI("Notifying userspace skipped. Callback is NULL");
    }
    pthread_mutex_unlock(&usb->mLock);
}

Return<void> Usb::queryPortStatus() {
    hidl_vec<PortStatus> currentPortStatus_1_2;

    queryVersionHelper(this, &currentPortStatus_1_2);
    return Void();
}

Return<void> Usb::enableContaminantPresenceDetection(const hidl_string & /*portName*/,
                                                     bool /*enable*/) {
    hidl_vec<PortStatus> currentPortStatus_1_2;

    queryVersionHelper(this, &currentPortStatus_1_2);
    return Void();
}

Return<void> Usb::enableContaminantPresenceProtection(const hidl_string & /*portName*/,
                                                      bool /*enable*/) {
    hidl_vec<PortStatus> currentPortStatus_1_2;

    queryVersionHelper(this, &currentPortStatus_1_2);
    return Void();
}

/* uevent_event() data that is persistent across uevents. */
struct data {
  int uevent_fd;
  android::hardware::usb::V1_3::implementation::Usb *usb;
};

// Report connection & disconnection of devices into the USB-C connector.
static void uevent_event(uint32_t /*epevents*/, struct data *payload) {
    char msg[UEVENT_MSG_LEN + 2];
    char *cp;
    int n;

    n = uevent_kernel_multicast_recv(payload->uevent_fd, msg, UEVENT_MSG_LEN);
    if (n <= 0)
        return;
    if (n >= UEVENT_MSG_LEN) /* overflow -- discard */
        return;

    msg[n] = '\0';
    msg[n + 1] = '\0';
    cp = msg;

    while (*cp) {
        if (std::regex_match(cp, std::regex("(add)(.*)(-partner)"))) {
            ALOGI("partner added");
            pthread_mutex_lock(&payload->usb->mPartnerLock);
            payload->usb->mPartnerUp = true;
            pthread_cond_signal(&payload->usb->mPartnerCV);
            pthread_mutex_unlock(&payload->usb->mPartnerLock);
        } else if (!strncmp(cp, "DEVTYPE=typec_", strlen("DEVTYPE=typec_"))) {
            hidl_vec<PortStatus> currentPortStatus_1_2;
            queryVersionHelper(payload->usb, &currentPortStatus_1_2);

            // Role switch is not in progress and port is in disconnected state
            if (!pthread_mutex_trylock(&payload->usb->mRoleSwitchLock)) {
                for (unsigned long i = 0; i < currentPortStatus_1_2.size(); i++) {
                    DIR *dp =
                        opendir(std::string("/sys/class/typec/" +
                                            std::string(currentPortStatus_1_2[i]
                                                            .status_1_1.status.portName.c_str()) +
                                            "-partner")
                                    .c_str());
                    if (dp == NULL) {
                        // PortRole role = {.role = static_cast<uint32_t>(PortMode::UFP)};
                        switchToDrp(currentPortStatus_1_2[i].status_1_1.status.portName);
                    } else {
                        closedir(dp);
                    }
                }
                pthread_mutex_unlock(&payload->usb->mRoleSwitchLock);
            }
            break;
        }
        /* advance to after the next \0 */
        while (*cp++) {
        }
    }
}

void *work(void *param) {
  int epoll_fd, uevent_fd;
  struct epoll_event ev;
  int nevents = 0;
  struct data payload;

  ALOGE("creating thread");

  uevent_fd = uevent_open_socket(64 * 1024, true);

  if (uevent_fd < 0) {
    ALOGE("uevent_init: uevent_open_socket failed\n");
    return NULL;
  }

  payload.uevent_fd = uevent_fd;
  payload.usb = (android::hardware::usb::V1_3::implementation::Usb *)param;

  fcntl(uevent_fd, F_SETFL, O_NONBLOCK);

  ev.events = EPOLLIN;
  ev.data.ptr = (void *)uevent_event;

  epoll_fd = epoll_create1(EPOLL_CLOEXEC);
  if (epoll_fd == -1) {
    ALOGE("epoll_create1 failed; errno=%d", errno);
    goto error;
  }

  if (epoll_ctl(epoll_fd, EPOLL_CTL_ADD, uevent_fd, &ev) == -1) {
    ALOGE("epoll_ctl failed; errno=%d", errno);
    goto error;
  }

  while (!destroyThread) {
    struct epoll_event events[64];

    nevents = epoll_wait(epoll_fd, events, 64, -1);
    if (nevents == -1) {
      if (errno == EINTR) continue;
      ALOGE("usb epoll_wait failed; errno=%d", errno);
      break;
    }

    for (int n = 0; n < nevents; ++n) {
      if (events[n].data.ptr)
        (*(void (*)(int, struct data *payload))events[n].data.ptr)(
            events[n].events, &payload);
    }
  }

  ALOGI("exiting worker thread");
error:
  close(uevent_fd);

  if (epoll_fd >= 0) close(epoll_fd);

  return NULL;
}

void sighandler(int sig) {
  if (sig == SIGUSR1) {
    destroyThread = true;
    ALOGI("destroy set");
    return;
  }
  signal(SIGUSR1, sighandler);
}

Return<void> Usb::setCallback(const sp<V1_0::IUsbCallback> &callback) {
    sp<V1_1::IUsbCallback> callback_V1_1 = V1_1::IUsbCallback::castFrom(callback);
    sp<IUsbCallback> callback_V1_2 = IUsbCallback::castFrom(callback);

    if (callback != NULL) {
        if (callback_V1_2 != NULL)
            ALOGI("Registering 1.2 callback");
        else if (callback_V1_1 != NULL)
            ALOGI("Registering 1.1 callback");
    }

    pthread_mutex_lock(&mLock);
    /*
     * When both the old callback and new callback values are NULL,
     * there is no need to spin off the worker thread.
     * When both the values are not NULL, we would already have a
     * worker thread running, so updating the callback object would
     * be suffice.
     */
    if ((mCallback_1_0 == NULL && callback == NULL) ||
        (mCallback_1_0 != NULL && callback != NULL)) {
        /*
         * Always store as V1_0 callback object. Type cast to V1_1
         * when the callback is actually invoked.
         */
        mCallback_1_0 = callback;
        pthread_mutex_unlock(&mLock);
        return Void();
    }

    mCallback_1_0 = callback;
    ALOGI("registering callback");

    // Kill the worker thread if the new callback is NULL.
    if (mCallback_1_0 == NULL) {
        pthread_mutex_unlock(&mLock);
        if (!pthread_kill(mPoll, SIGUSR1)) {
            pthread_join(mPoll, NULL);
            ALOGI("pthread destroyed");
        }
        return Void();
    }

    destroyThread = false;
    signal(SIGUSR1, sighandler);

    /*
     * Create a background thread if the old callback value is NULL
     * and being updated with a new value.
     */
    if (pthread_create(&mPoll, NULL, work, this)) {
        ALOGE("pthread creation failed %d", errno);
        mCallback_1_0 = NULL;
    }

    pthread_mutex_unlock(&mLock);
    return Void();
}

}  // namespace implementation
}  // namespace V1_3
}  // namespace usb
}  // namespace hardware
}  // namespace android