text: /* -*- Mode: C; indent-tabs-mode:nil -*- */
  /*
   * darwin backend for libusbx 1.0
   * Copyright © 2008-2013 Nathan Hjelm <hjelmn@users.sourceforge.net>
   *
   * This library is free software; you can redistribute it and/or
   * modify it under the terms of the GNU Lesser General Public
   * License as published by the Free Software Foundation; either
   * version 2.1 of the License, or (at your option) any later version.
   *
   * This library is distributed in the hope that it will be useful,
   * but WITHOUT ANY WARRANTY; without even the implied warranty of
   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   * Lesser General Public License for more details.
   *
   * You should have received a copy of the GNU Lesser General Public
   * License along with this library; if not, write to the Free Software
   * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
   */
  
  #include "config.h"
  #include <ctype.h>
  #include <errno.h>
  #include <pthread.h>
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  #include <sys/types.h>
  #include <unistd.h>
  #include <fcntl.h>
  #include <libkern/OSAtomic.h>
  
  #include <mach/clock.h>
  #include <mach/clock_types.h>
  #include <mach/mach_host.h>
  #include <mach/mach_port.h>
  
  #include <AvailabilityMacros.h>
  #if MAC_OS_X_VERSION_MIN_REQUIRED >= 1060
    #include <objc/objc-auto.h>
  #endif
  
  #include "darwin_usb.h"
  
  /* async event thread */
  static pthread_mutex_t libusb_darwin_at_mutex = PTHREAD_MUTEX_INITIALIZER;
  static pthread_cond_t  libusb_darwin_at_cond = PTHREAD_COND_INITIALIZER;
  
  static clock_serv_t clock_realtime;
  static clock_serv_t clock_monotonic;
  
  static CFRunLoopRef libusb_darwin_acfl = NULL; /* event cf loop */
  static volatile int32_t initCount = 0;
  
  static usbi_mutex_t darwin_cached_devices_lock = PTHREAD_MUTEX_INITIALIZER;
  static struct list_head darwin_cached_devices = {&darwin_cached_devices, &darwin_cached_devices};
  
  #define DARWIN_CACHED_DEVICE(a) ((struct darwin_cached_device *) (((struct darwin_device_priv *)((a)->os_priv))->dev))
  
  /* async event thread */
  static pthread_t libusb_darwin_at;
  
  static int darwin_get_config_descriptor(struct libusb_device *dev, uint8_t config_index, unsigned char *buffer, size_t len, int *host_endian);
  static int darwin_claim_interface(struct libusb_device_handle *dev_handle, int iface);
  static int darwin_release_interface(struct libusb_device_handle *dev_handle, int iface);
  static int darwin_reset_device(struct libusb_device_handle *dev_handle);
  static void darwin_async_io_callback (void *refcon, IOReturn result, void *arg0);
  
  static int darwin_scan_devices(struct libusb_context *ctx);
  static int process_new_device (struct libusb_context *ctx, io_service_t service);
  
  #if defined(ENABLE_LOGGING)
  static const char *darwin_error_str (int result) {
    static char string_buffer[50];
    switch (result) {
    case kIOReturnSuccess:
      return "no error";
    case kIOReturnNotOpen:
      return "device not opened for exclusive access";
    case kIOReturnNoDevice:
      return "no connection to an IOService";
    case kIOUSBNoAsyncPortErr:
      return "no async port has been opened for interface";
    case kIOReturnExclusiveAccess:
      return "another process has device opened for exclusive access";
    case kIOUSBPipeStalled:
      return "pipe is stalled";
    case kIOReturnError:
      return "could not establish a connection to the Darwin kernel";
    case kIOUSBTransactionTimeout:
      return "transaction timed out";
    case kIOReturnBadArgument:
      return "invalid argument";
    case kIOReturnAborted:
      return "transaction aborted";
    case kIOReturnNotResponding:
      return "device not responding";
    case kIOReturnOverrun:
      return "data overrun";
    case kIOReturnCannotWire:
      return "physical memory can not be wired down";
    case kIOReturnNoResources:
      return "out of resources";
    case kIOUSBHighSpeedSplitError:
      return "high speed split error";
    default:
      snprintf(string_buffer, sizeof(string_buffer), "unknown error (0x%x)", result);
      return string_buffer;
    }
  }
  #endif
  
  static int darwin_to_libusb (int result) {
    switch (result) {
    case kIOReturnUnderrun:
    case kIOReturnSuccess:
      return LIBUSB_SUCCESS;
    case kIOReturnNotOpen:
    case kIOReturnNoDevice:
      return LIBUSB_ERROR_NO_DEVICE;
    case kIOReturnExclusiveAccess:
      return LIBUSB_ERROR_ACCESS;
    case kIOUSBPipeStalled:
      return LIBUSB_ERROR_PIPE;
    case kIOReturnBadArgument:
      return LIBUSB_ERROR_INVALID_PARAM;
    case kIOUSBTransactionTimeout:
      return LIBUSB_ERROR_TIMEOUT;
    case kIOReturnNotResponding:
    case kIOReturnAborted:
    case kIOReturnError:
    case kIOUSBNoAsyncPortErr:
    default:
      return LIBUSB_ERROR_OTHER;
    }
  }
  
  /* this function must be called with the darwin_cached_devices_lock held */
  static void darwin_deref_cached_device(struct darwin_cached_device *cached_dev) {
    cached_dev->refcount--;
    /* free the device and remove it from the cache */
    if (0 == cached_dev->refcount) {
      list_del(&cached_dev->list);
  
      (*(cached_dev->device))->Release(cached_dev->device);
      free (cached_dev);
    }
  }
  
  static void darwin_ref_cached_device(struct darwin_cached_device *cached_dev) {
    cached_dev->refcount++;
  }
  
  static int ep_to_pipeRef(struct libusb_device_handle *dev_handle, uint8_t ep, uint8_t *pipep, uint8_t *ifcp) {
    struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)dev_handle->os_priv;
  
    /* current interface */
    struct darwin_interface *cInterface;
  
    int8_t i, iface;
  
    usbi_dbg ("converting ep address 0x%02x to pipeRef and interface", ep);
  
    for (iface = 0 ; iface < USB_MAXINTERFACES ; iface++) {
      cInterface = &priv->interfaces[iface];
  
      if (dev_handle->claimed_interfaces & (1 << iface)) {
        for (i = 0 ; i < cInterface->num_endpoints ; i++) {
          if (cInterface->endpoint_addrs[i] == ep) {
            *pipep = i + 1;
            *ifcp = iface;
            usbi_dbg ("pipe %d on interface %d matches", *pipep, *ifcp);
            return 0;
          }
        }
      }
    }
  
    /* No pipe found with the correct endpoint address */
    usbi_warn (HANDLE_CTX(dev_handle), "no pipeRef found with endpoint address 0x%02x.", ep);
  
    return -1;
  }
  
  static int usb_setup_device_iterator (io_iterator_t *deviceIterator, UInt32 location) {
    CFMutableDictionaryRef matchingDict = IOServiceMatching(kIOUSBDeviceClassName);
  
    if (!matchingDict)
      return kIOReturnError;
  
    if (location) {
      CFMutableDictionaryRef propertyMatchDict = CFDictionaryCreateMutable(kCFAllocatorDefault, 0,
                                                                           &kCFTypeDictionaryKeyCallBacks,
                                                                           &kCFTypeDictionaryValueCallBacks);
  
      if (propertyMatchDict) {
        /* there are no unsigned CFNumber types so treat the value as signed. the os seems to do this
           internally (CFNumberType of locationID is 3) */
        CFTypeRef locationCF = CFNumberCreate (NULL, kCFNumberSInt32Type, &location);
  
        CFDictionarySetValue (propertyMatchDict, CFSTR(kUSBDevicePropertyLocationID), locationCF);
        /* release our reference to the CFNumber (CFDictionarySetValue retains it) */
        CFRelease (locationCF);
  
        CFDictionarySetValue (matchingDict, CFSTR(kIOPropertyMatchKey), propertyMatchDict);
        /* release out reference to the CFMutableDictionaryRef (CFDictionarySetValue retains it) */
        CFRelease (propertyMatchDict);
      }
      /* else we can still proceed as long as the caller accounts for the possibility of other devices in the iterator */
    }
  
    return IOServiceGetMatchingServices(kIOMasterPortDefault, matchingDict, deviceIterator);
  }
  
  /* Returns 1 on success, 0 on failure. */
  static int get_ioregistry_value_number (io_service_t service, CFStringRef property, CFNumberType type, void *p) {
    CFTypeRef cfNumber = IORegistryEntryCreateCFProperty (service, property, kCFAllocatorDefault, 0);
    int ret = 0;
  
    if (cfNumber) {
      if (CFGetTypeID(cfNumber) == CFNumberGetTypeID()) {
        ret = CFNumberGetValue(cfNumber, type, p);
      }
  
      CFRelease (cfNumber);
    }
  
    return ret;
  }
  
  static usb_device_t **darwin_device_from_service (io_service_t service)
  {
    io_cf_plugin_ref_t *plugInInterface = NULL;
    usb_device_t **device;
    kern_return_t result;
    SInt32 score;
  
    result = IOCreatePlugInInterfaceForService(service, kIOUSBDeviceUserClientTypeID,
                                               kIOCFPlugInInterfaceID, &plugInInterface,
                                               &score);
  
    if (kIOReturnSuccess != result || !plugInInterface) {
      usbi_dbg ("could not set up plugin for service: %s\n", darwin_error_str (result));
      return NULL;
    }
  
    (void)(*plugInInterface)->QueryInterface(plugInInterface, CFUUIDGetUUIDBytes(DeviceInterfaceID),
                                             (LPVOID)&device);
    /* Use release instead of IODestroyPlugInInterface to avoid stopping IOServices associated with this device */
    (*plugInInterface)->Release (plugInInterface);
  
    return device;
  }
  
  static void darwin_devices_attached (void *ptr, io_iterator_t add_devices) {
    struct libusb_context *ctx;
    io_service_t service;
  
    usbi_mutex_lock(&active_contexts_lock);
  
    while ((service = IOIteratorNext(add_devices))) {
      /* add this device to each active context's device list */
      list_for_each_entry(ctx, &active_contexts_list, list, struct libusb_context) {
        process_new_device (ctx, service);;
      }
  
      IOObjectRelease(service);
    }
  
    usbi_mutex_unlock(&active_contexts_lock);
  }
  
  static void darwin_devices_detached (void *ptr, io_iterator_t rem_devices) {
    struct libusb_device *dev = NULL;
    struct libusb_context *ctx;
  
    io_service_t device;
    UInt64 session;
    int ret;
  
    while ((device = IOIteratorNext (rem_devices)) != 0) {
      /* get the location from the i/o registry */
      ret = get_ioregistry_value_number (device, CFSTR("sessionID"), kCFNumberSInt64Type, &session);
      IOObjectRelease (device);
      if (!ret)
        continue;
  
      usbi_mutex_lock(&active_contexts_lock);
  
      list_for_each_entry(ctx, &active_contexts_list, list, struct libusb_context) {
        usbi_dbg ("notifying context %p of device disconnect", ctx);
  
        dev = usbi_get_device_by_session_id(ctx, (unsigned long) session);
        if (dev) {
          /* signal the core that this device has been disconnected. the core will tear down this device
             when the reference count reaches 0 */
          usbi_disconnect_device(dev);
          libusb_unref_device(dev);
        }
      }
  
      usbi_mutex_unlock(&active_contexts_lock);
    }
  }
  
  static void darwin_clear_iterator (io_iterator_t iter) {
    io_service_t device;
  
    while ((device = IOIteratorNext (iter)) != 0)
      IOObjectRelease (device);
  }
  
  static void *darwin_event_thread_main (void *arg0) {
    IOReturn kresult;
    struct libusb_context *ctx = (struct libusb_context *)arg0;
    CFRunLoopRef runloop;
  
    /* Set this thread's name, so it can be seen in the debugger
       and crash reports. */
  #if MAC_OS_X_VERSION_MIN_REQUIRED >= 1060
    pthread_setname_np ("org.libusb.device-hotplug");
  
    /* Tell the Objective-C garbage collector about this thread.
       This is required because, unlike NSThreads, pthreads are
       not automatically registered. Although we don't use
       Objective-C, we use CoreFoundation, which does. */
    objc_registerThreadWithCollector();
  #endif
  
    /* hotplug (device arrival/removal) sources */
    CFRunLoopSourceRef     libusb_notification_cfsource;
    io_notification_port_t libusb_notification_port;
    io_iterator_t          libusb_rem_device_iterator;
    io_iterator_t          libusb_add_device_iterator;
  
    usbi_dbg ("creating hotplug event source");
  
    runloop = CFRunLoopGetCurrent ();
    CFRetain (runloop);
  
    /* add the notification port to the run loop */
    libusb_notification_port     = IONotificationPortCreate (kIOMasterPortDefault);
    libusb_notification_cfsource = IONotificationPortGetRunLoopSource (libusb_notification_port);
    CFRunLoopAddSource(runloop, libusb_notification_cfsource, kCFRunLoopDefaultMode);
  
    /* create notifications for removed devices */
    kresult = IOServiceAddMatchingNotification (libusb_notification_port, kIOTerminatedNotification,
                                                IOServiceMatching(kIOUSBDeviceClassName),
                                                (IOServiceMatchingCallback)darwin_devices_detached,
                                                (void *)ctx, &libusb_rem_device_iterator);
  
    if (kresult != kIOReturnSuccess) {
      usbi_err (ctx, "could not add hotplug event source: %s", darwin_error_str (kresult));
  
      pthread_exit (NULL);
    }
  
    /* create notifications for attached devices */
    kresult = IOServiceAddMatchingNotification(libusb_notification_port, kIOFirstMatchNotification,
                                                IOServiceMatching(kIOUSBDeviceClassName),
                                                (IOServiceMatchingCallback)darwin_devices_attached,
                                                (void *)ctx, &libusb_add_device_iterator);
  
    if (kresult != kIOReturnSuccess) {
      usbi_err (ctx, "could not add hotplug event source: %s", darwin_error_str (kresult));
  
      pthread_exit (NULL);
    }
  
    /* arm notifiers */
    darwin_clear_iterator (libusb_rem_device_iterator);
    darwin_clear_iterator (libusb_add_device_iterator);
  
    usbi_dbg ("darwin event thread ready to receive events");
  
    /* signal the main thread that the hotplug runloop has been created. */
    pthread_mutex_lock (&libusb_darwin_at_mutex);
    libusb_darwin_acfl = runloop;
    pthread_cond_signal (&libusb_darwin_at_cond);
    pthread_mutex_unlock (&libusb_darwin_at_mutex);
  
    /* run the runloop */
    CFRunLoopRun();
  
    usbi_dbg ("darwin event thread exiting");
  
    /* remove the notification cfsource */
    CFRunLoopRemoveSource(runloop, libusb_notification_cfsource, kCFRunLoopDefaultMode);
  
    /* delete notification port */
    IONotificationPortDestroy (libusb_notification_port);
  
    /* delete iterators */
    IOObjectRelease (libusb_rem_device_iterator);
    IOObjectRelease (libusb_add_device_iterator);
  
    CFRelease (runloop);
  
    libusb_darwin_acfl = NULL;
  
    pthread_exit (NULL);
  }
  
  static void _darwin_finalize(void) {
    struct darwin_cached_device *dev, *next;
  
    usbi_mutex_lock(&darwin_cached_devices_lock);
    list_for_each_entry_safe(dev, next, &darwin_cached_devices, list, struct darwin_cached_device) {
      darwin_deref_cached_device(dev);
    }
    usbi_mutex_unlock(&darwin_cached_devices_lock);
  }
  
  static int darwin_init(struct libusb_context *ctx) {
    host_name_port_t host_self;
    static int initted = 0;
    int rc;
  
    rc = darwin_scan_devices (ctx);
    if (LIBUSB_SUCCESS != rc) {
      return rc;
    }
  
    if (OSAtomicIncrement32Barrier(&initCount) == 1) {
      /* create the clocks that will be used */
  
      if (!initted) {
        initted = 1;
        atexit(_darwin_finalize);
      }
  
      host_self = mach_host_self();
      host_get_clock_service(host_self, CALENDAR_CLOCK, &clock_realtime);
      host_get_clock_service(host_self, SYSTEM_CLOCK, &clock_monotonic);
      mach_port_deallocate(mach_task_self(), host_self);
  
      pthread_create (&libusb_darwin_at, NULL, darwin_event_thread_main, (void *)ctx);
  
      pthread_mutex_lock (&libusb_darwin_at_mutex);
      while (!libusb_darwin_acfl)
        pthread_cond_wait (&libusb_darwin_at_cond, &libusb_darwin_at_mutex);
      pthread_mutex_unlock (&libusb_darwin_at_mutex);
    }
  
    return rc;
  }
  
  static void darwin_exit (void) {
    if (OSAtomicDecrement32Barrier(&initCount) == 0) {
      mach_port_deallocate(mach_task_self(), clock_realtime);
      mach_port_deallocate(mach_task_self(), clock_monotonic);
  
      /* stop the event runloop and wait for the thread to terminate. */
      CFRunLoopStop (libusb_darwin_acfl);
      pthread_join (libusb_darwin_at, NULL);
    }
  }
  
  static int darwin_get_device_descriptor(struct libusb_device *dev, unsigned char *buffer, int *host_endian) {
    struct darwin_cached_device *priv = DARWIN_CACHED_DEVICE(dev);
  
    /* return cached copy */
    memmove (buffer, &(priv->dev_descriptor), DEVICE_DESC_LENGTH);
  
    *host_endian = 0;
  
    return 0;
  }
  
  static int get_configuration_index (struct libusb_device *dev, int config_value) {
    struct darwin_cached_device *priv = DARWIN_CACHED_DEVICE(dev);
    UInt8 i, numConfig;
    IOUSBConfigurationDescriptorPtr desc;
    IOReturn kresult;
  
    /* is there a simpler way to determine the index? */
    kresult = (*(priv->device))->GetNumberOfConfigurations (priv->device, &numConfig);
    if (kresult != kIOReturnSuccess)
      return darwin_to_libusb (kresult);
  
    for (i = 0 ; i < numConfig ; i++) {
      (*(priv->device))->GetConfigurationDescriptorPtr (priv->device, i, &desc);
  
      if (desc->bConfigurationValue == config_value)
        return i;
    }
  
    /* configuration not found */
    return LIBUSB_ERROR_NOT_FOUND;
  }
  
  static int darwin_get_active_config_descriptor(struct libusb_device *dev, unsigned char *buffer, size_t len, int *host_endian) {
    struct darwin_cached_device *priv = DARWIN_CACHED_DEVICE(dev);
    int config_index;
  
    if (0 == priv->active_config)
      return LIBUSB_ERROR_NOT_FOUND;
  
    config_index = get_configuration_index (dev, priv->active_config);
    if (config_index < 0)
      return config_index;
  
    return darwin_get_config_descriptor (dev, config_index, buffer, len, host_endian);
  }
  
  static int darwin_get_config_descriptor(struct libusb_device *dev, uint8_t config_index, unsigned char *buffer, size_t len, int *host_endian) {
    struct darwin_cached_device *priv = DARWIN_CACHED_DEVICE(dev);
    IOUSBConfigurationDescriptorPtr desc;
    IOReturn kresult;
    int ret;
  
    if (!priv || !priv->device)
      return LIBUSB_ERROR_OTHER;
  
    kresult = (*priv->device)->GetConfigurationDescriptorPtr (priv->device, config_index, &desc);
    if (kresult == kIOReturnSuccess) {
      /* copy descriptor */
      if (libusb_le16_to_cpu(desc->wTotalLength) < len)
        len = libusb_le16_to_cpu(desc->wTotalLength);
  
      memmove (buffer, desc, len);
  
      /* GetConfigurationDescriptorPtr returns the descriptor in USB bus order */
      *host_endian = 0;
    }
  
    ret = darwin_to_libusb (kresult);
    if (ret != LIBUSB_SUCCESS)
      return ret;
  
    return len;
  }
  
  /* check whether the os has configured the device */
  static int darwin_check_configuration (struct libusb_context *ctx, struct darwin_cached_device *dev) {
    usb_device_t **darwin_device = dev->device;
  
    IOUSBConfigurationDescriptorPtr configDesc;
    IOUSBFindInterfaceRequest request;
    kern_return_t             kresult;
    io_iterator_t             interface_iterator;
    io_service_t              firstInterface;
  
    if (dev->dev_descriptor.bNumConfigurations < 1) {
      usbi_err (ctx, "device has no configurations");
      return LIBUSB_ERROR_OTHER; /* no configurations at this speed so we can't use it */
    }
  
    /* find the first configuration */
    kresult = (*darwin_device)->GetConfigurationDescriptorPtr (darwin_device, 0, &configDesc);
    dev->first_config = (kIOReturnSuccess == kresult) ? configDesc->bConfigurationValue : 1;
  
    /* check if the device is already configured. there is probably a better way than iterating over the
       to accomplish this (the trick is we need to avoid a call to GetConfigurations since buggy devices
       might lock up on the device request) */
  
    /* Setup the Interface Request */
    request.bInterfaceClass    = kIOUSBFindInterfaceDontCare;
    request.bInterfaceSubClass = kIOUSBFindInterfaceDontCare;
    request.bInterfaceProtocol = kIOUSBFindInterfaceDontCare;
    request.bAlternateSetting  = kIOUSBFindInterfaceDontCare;
  
    kresult = (*(darwin_device))->CreateInterfaceIterator(darwin_device, &request, &interface_iterator);
    if (kresult)
      return darwin_to_libusb (kresult);
  
    /* iterate once */
    firstInterface = IOIteratorNext(interface_iterator);
  
    /* done with the interface iterator */
    IOObjectRelease(interface_iterator);
  
    if (firstInterface) {
      IOObjectRelease (firstInterface);
  
      /* device is configured */
      if (dev->dev_descriptor.bNumConfigurations == 1)
        /* to avoid problems with some devices get the configurations value from the configuration descriptor */
        dev->active_config = dev->first_config;
      else
        /* devices with more than one configuration should work with GetConfiguration */
        (*darwin_device)->GetConfiguration (darwin_device, &dev->active_config);
    } else
      /* not configured */
      dev->active_config = 0;
    
    usbi_dbg ("active config: %u, first config: %u", dev->active_config, dev->first_config);
  
    return 0;
  }
  
  static int darwin_request_descriptor (usb_device_t **device, UInt8 desc, UInt8 desc_index, void *buffer, size_t buffer_size) {
    IOUSBDevRequestTO req;
  
    memset (buffer, 0, buffer_size);
  
    /* Set up request for descriptor/ */
    req.bmRequestType = USBmakebmRequestType(kUSBIn, kUSBStandard, kUSBDevice);
    req.bRequest      = kUSBRqGetDescriptor;
    req.wValue        = desc << 8;
    req.wIndex        = desc_index;
    req.wLength       = buffer_size;
    req.pData         = buffer;
    req.noDataTimeout = 20;
    req.completionTimeout = 100;
  
    return (*device)->DeviceRequestTO (device, &req);
  }
  
  static int darwin_cache_device_descriptor (struct libusb_context *ctx, struct darwin_cached_device *dev) {
    usb_device_t **device = dev->device;
    int retries = 1, delay = 30000;
    int unsuspended = 0, try_unsuspend = 1, try_reconfigure = 1;
    int is_open = 0;
    int ret = 0, ret2;
    UInt8 bDeviceClass;
    UInt16 idProduct, idVendor;
  
    dev->can_enumerate = 0;
  
    (*device)->GetDeviceClass (device, &bDeviceClass);
    (*device)->GetDeviceProduct (device, &idProduct);
    (*device)->GetDeviceVendor (device, &idVendor);
  
    /* According to Apple's documentation the device must be open for DeviceRequest but we may not be able to open some
     * devices and Apple's USB Prober doesn't bother to open the device before issuing a descriptor request.  Still,
     * to follow the spec as closely as possible, try opening the device */
    is_open = ((*device)->USBDeviceOpenSeize(device) == kIOReturnSuccess);
  
    do {
      /**** retrieve device descriptor ****/
      ret = darwin_request_descriptor (device, kUSBDeviceDesc, 0, &dev->dev_descriptor, sizeof(dev->dev_descriptor));
  
      if (kIOReturnOverrun == ret && kUSBDeviceDesc == dev->dev_descriptor.bDescriptorType)
        /* received an overrun error but we still received a device descriptor */
        ret = kIOReturnSuccess;
  
      if (kIOUSBVendorIDAppleComputer == idVendor) {
        /* NTH: don't bother retrying or unsuspending Apple devices */
        break;
      }
  
      if (kIOReturnSuccess == ret && (0 == dev->dev_descriptor.bNumConfigurations ||
                                      0 == dev->dev_descriptor.bcdUSB)) {
        /* work around for incorrectly configured devices */
        if (try_reconfigure && is_open) {
          usbi_dbg("descriptor appears to be invalid. resetting configuration before trying again...");
  
          /* set the first configuration */
          (*device)->SetConfiguration(device, 1);
  
          /* don't try to reconfigure again */
          try_reconfigure = 0;
        }
  
        ret = kIOUSBPipeStalled;
      }
  
      if (kIOReturnSuccess != ret && is_open && try_unsuspend) {
        /* device may be suspended. unsuspend it and try again */
  #if DeviceVersion >= 320
        UInt32 info = 0;
  
        /* IOUSBFamily 320+ provides a way to detect device suspension but earlier versions do not */
        (void)(*device)->GetUSBDeviceInformation (device, &info);
  
        /* note that the device was suspended */
        if (info & (1 << kUSBInformationDeviceIsSuspendedBit) || 0 == info)
          try_unsuspend = 1;
  #endif
  
        if (try_unsuspend) {
          /* try to unsuspend the device */
          ret2 = (*device)->USBDeviceSuspend (device, 0);
          if (kIOReturnSuccess != ret2) {
            /* prevent log spew from poorly behaving devices.  this indicates the
               os actually had trouble communicating with the device */
            usbi_dbg("could not retrieve device descriptor. failed to unsuspend: %s",darwin_error_str(ret2));
          } else
            unsuspended = 1;
  
          try_unsuspend = 0;
        }
      }
  
      if (kIOReturnSuccess != ret) {
        usbi_dbg("kernel responded with code: 0x%08x. sleeping for %d ms before trying again", ret, delay/1000);
        /* sleep for a little while before trying again */
        usleep (delay);
      }
    } while (kIOReturnSuccess != ret && retries--);
  
    if (unsuspended)
      /* resuspend the device */
      (void)(*device)->USBDeviceSuspend (device, 1);
  
    if (is_open)
      (void) (*device)->USBDeviceClose (device);
  
    if (ret != kIOReturnSuccess) {
      /* a debug message was already printed out for this error */
      if (LIBUSB_CLASS_HUB == bDeviceClass)
        usbi_dbg ("could not retrieve device descriptor %.4x:%.4x: %s (%x). skipping device",
                  idVendor, idProduct, darwin_error_str (ret), ret);
      else
        usbi_warn (ctx, "could not retrieve device descriptor %.4x:%.4x: %s (%x). skipping device",
                   idVendor, idProduct, darwin_error_str (ret), ret);
      return darwin_to_libusb (ret);
    }
  
    /* catch buggy hubs (which appear to be virtual). Apple's own USB prober has problems with these devices. */
    if (libusb_le16_to_cpu (dev->dev_descriptor.idProduct) != idProduct) {
      /* not a valid device */
      usbi_warn (ctx, "idProduct from iokit (%04x) does not match idProduct in descriptor (%04x). skipping device",
                 idProduct, libusb_le16_to_cpu (dev->dev_descriptor.idProduct));
      return LIBUSB_ERROR_NO_DEVICE;
    }
  
    usbi_dbg ("cached device descriptor:");
    usbi_dbg ("  bDescriptorType:    0x%02x", dev->dev_descriptor.bDescriptorType);
    usbi_dbg ("  bcdUSB:             0x%04x", dev->dev_descriptor.bcdUSB);
    usbi_dbg ("  bDeviceClass:       0x%02x", dev->dev_descriptor.bDeviceClass);
    usbi_dbg ("  bDeviceSubClass:    0x%02x", dev->dev_descriptor.bDeviceSubClass);
    usbi_dbg ("  bDeviceProtocol:    0x%02x", dev->dev_descriptor.bDeviceProtocol);
    usbi_dbg ("  bMaxPacketSize0:    0x%02x", dev->dev_descriptor.bMaxPacketSize0);
    usbi_dbg ("  idVendor:           0x%04x", dev->dev_descriptor.idVendor);
    usbi_dbg ("  idProduct:          0x%04x", dev->dev_descriptor.idProduct);
    usbi_dbg ("  bcdDevice:          0x%04x", dev->dev_descriptor.bcdDevice);
    usbi_dbg ("  iManufacturer:      0x%02x", dev->dev_descriptor.iManufacturer);
    usbi_dbg ("  iProduct:           0x%02x", dev->dev_descriptor.iProduct);
    usbi_dbg ("  iSerialNumber:      0x%02x", dev->dev_descriptor.iSerialNumber);
    usbi_dbg ("  bNumConfigurations: 0x%02x", dev->dev_descriptor.bNumConfigurations);
  
    dev->can_enumerate = 1;
  
    return LIBUSB_SUCCESS;
  }
  
  static int darwin_get_cached_device(struct libusb_context *ctx, io_service_t service,
                                      struct darwin_cached_device **cached_out) {
    struct darwin_cached_device *new_device;
    UInt64 sessionID = 0, parent_sessionID = 0;
    int ret = LIBUSB_SUCCESS;
    usb_device_t **device;
    io_service_t parent;
    kern_return_t result;
    UInt8 port = 0;
  
    /* get some info from the io registry */
    (void) get_ioregistry_value_number (service, CFSTR("sessionID"), kCFNumberSInt64Type, &sessionID);
    (void) get_ioregistry_value_number (service, CFSTR("PortNum"), kCFNumberSInt8Type, &port);
  
    usbi_dbg("finding cached device for sessionID 0x%" PRIx64, sessionID);
  
    result = IORegistryEntryGetParentEntry (service, kIOUSBPlane, &parent);
  
    if (kIOReturnSuccess == result) {
      (void) get_ioregistry_value_number (parent, CFSTR("sessionID"), kCFNumberSInt64Type, &parent_sessionID);
      IOObjectRelease(parent);
    }
  
    usbi_mutex_lock(&darwin_cached_devices_lock);
    do {
      *cached_out = NULL;
  
      list_for_each_entry(new_device, &darwin_cached_devices, list, struct darwin_cached_device) {
        usbi_dbg("matching sessionID 0x%" PRIx64 " against cached device with sessionID 0x%" PRIx64, sessionID, new_device->session);
        if (new_device->session == sessionID) {
          usbi_dbg("using cached device for device");
          *cached_out = new_device;
          break;
        }
      }
  
      if (*cached_out)
        break;
  
      usbi_dbg("caching new device with sessionID 0x%" PRIx64, sessionID);
  
      device = darwin_device_from_service (service);
      if (!device) {
        ret = LIBUSB_ERROR_NO_DEVICE;
        break;
      }
  
      new_device = calloc (1, sizeof (*new_device));
      if (!new_device) {
        ret = LIBUSB_ERROR_NO_MEM;
        break;
      }
  
      /* add this device to the cached device list */
      list_add(&new_device->list, &darwin_cached_devices);
  
      (*device)->GetDeviceAddress (device, (USBDeviceAddress *)&new_device->address);
  
      /* keep a reference to this device */
      darwin_ref_cached_device(new_device);
  
      new_device->device = device;
      new_device->session = sessionID;
      (*device)->GetLocationID (device, &new_device->location);
      new_device->port = port;
      new_device->parent_session = parent_sessionID;
  
      /* cache the device descriptor */
      ret = darwin_cache_device_descriptor(ctx, new_device);
      if (ret)
        break;
  
      if (new_device->can_enumerate) {
        snprintf(new_device->sys_path, 20, "%03i-%04x-%04x-%02x-%02x", new_device->address,
                 new_device->dev_descriptor.idVendor, new_device->dev_descriptor.idProduct,
                 new_device->dev_descriptor.bDeviceClass, new_device->dev_descriptor.bDeviceSubClass);
      }
    } while (0);
  
    usbi_mutex_unlock(&darwin_cached_devices_lock);
  
    /* keep track of devices regardless of if we successfully enumerate them to
       prevent them from being enumerated multiple times */
  
    *cached_out = new_device;
  
    return ret;
  }
  
  static int process_new_device (struct libusb_context *ctx, io_service_t service) {
    struct darwin_device_priv *priv;
    struct libusb_device *dev = NULL;
    struct darwin_cached_device *cached_device;
    UInt8 devSpeed;
    int ret = 0;
  
    do {
      ret = darwin_get_cached_device (ctx, service, &cached_device);
  
      if (ret < 0 || !cached_device->can_enumerate) {
        return ret;
      }
  
      /* check current active configuration (and cache the first configuration value--
         which may be used by claim_interface) */
      ret = darwin_check_configuration (ctx, cached_device);
      if (ret)
        break;
  
      usbi_dbg ("allocating new device in context %p for with session 0x%" PRIx64,
                ctx, cached_device->session);
  
      dev = usbi_alloc_device(ctx, (unsigned long) cached_device->session);
      if (!dev) {
        return LIBUSB_ERROR_NO_MEM;
      }
  
      priv = (struct darwin_device_priv *)dev->os_priv;
  
      priv->dev = cached_device;
      darwin_ref_cached_device (priv->dev);
  
      if (cached_device->parent_session > 0) {
        dev->parent_dev = usbi_get_device_by_session_id (ctx, (unsigned long) cached_device->parent_session);
      } else {
        dev->parent_dev = NULL;
      }
      dev->port_number    = cached_device->port;
      dev->bus_number     = cached_device->location >> 24;
      dev->device_address = cached_device->address;
  
      (*(priv->dev->device))->GetDeviceSpeed (priv->dev->device, &devSpeed);
  
      switch (devSpeed) {
      case kUSBDeviceSpeedLow: dev->speed = LIBUSB_SPEED_LOW; break;
      case kUSBDeviceSpeedFull: dev->speed = LIBUSB_SPEED_FULL; break;
      case kUSBDeviceSpeedHigh: dev->speed = LIBUSB_SPEED_HIGH; break;
  #if DeviceVersion >= 500
      case kUSBDeviceSpeedSuper: dev->speed = LIBUSB_SPEED_SUPER; break;
  #endif
      default:
        usbi_warn (ctx, "Got unknown device speed %d", devSpeed);
      }
  
      ret = usbi_sanitize_device (dev);
      if (ret < 0)
        break;
  
      usbi_dbg ("found device with address %d port = %d parent = %p at %p", dev->device_address,
                dev->port_number, (void *) dev->parent_dev, priv->dev->sys_path);
    } while (0);
  
    if (0 == ret) {
      usbi_connect_device (dev);
    } else {
      libusb_unref_device (dev);
    }
  
    return ret;
  }
  
  static int darwin_scan_devices(struct libusb_context *ctx) {
    io_iterator_t deviceIterator;
    io_service_t service;
    kern_return_t kresult;
  
    kresult = usb_setup_device_iterator (&deviceIterator, 0);
    if (kresult != kIOReturnSuccess)
      return darwin_to_libusb (kresult);
  
    while ((service = IOIteratorNext (deviceIterator))) {
      (void) process_new_device (ctx, service);
  
      IOObjectRelease(service);
    }
  
    IOObjectRelease(deviceIterator);
  
    return 0;
  }
  
  static int darwin_open (struct libusb_device_handle *dev_handle) {
    struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)dev_handle->os_priv;
    struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(dev_handle->dev);
    IOReturn kresult;
  
    if (0 == dpriv->open_count) {
      /* try to open the device */
      kresult = (*(dpriv->device))->USBDeviceOpenSeize (dpriv->device);
      if (kresult != kIOReturnSuccess) {
        usbi_warn (HANDLE_CTX (dev_handle), "USBDeviceOpen: %s", darwin_error_str(kresult));
  
        if (kIOReturnExclusiveAccess != kresult) {
          return darwin_to_libusb (kresult);
        }
  
        /* it is possible to perform some actions on a device that is not open so do not return an error */
        priv->is_open = 0;
      } else {
        priv->is_open = 1;
      }
  
      /* create async event source */
      kresult = (*(dpriv->device))->CreateDeviceAsyncEventSource (dpriv->device, &priv->cfSource);
      if (kresult != kIOReturnSuccess) {
        usbi_err (HANDLE_CTX (dev_handle), "CreateDeviceAsyncEventSource: %s", darwin_error_str(kresult));
  
        if (priv->is_open) {
          (*(dpriv->device))->USBDeviceClose (dpriv->device);
        }
  
        priv->is_open = 0;
  
        return darwin_to_libusb (kresult);
      }
  
      CFRetain (libusb_darwin_acfl);
  
      /* add the cfSource to the aync run loop */
      CFRunLoopAddSource(libusb_darwin_acfl, priv->cfSource, kCFRunLoopCommonModes);
    }
  
    /* device opened successfully */
    dpriv->open_count++;
  
    /* create a file descriptor for notifications */
    pipe (priv->fds);
  
    /* set the pipe to be non-blocking */
    fcntl (priv->fds[1], F_SETFD, O_NONBLOCK);
  
    usbi_add_pollfd(HANDLE_CTX(dev_handle), priv->fds[0], POLLIN);
  
    usbi_dbg ("device open for access");
  
    return 0;
  }
  
  static void darwin_close (struct libusb_device_handle *dev_handle) {
    struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)dev_handle->os_priv;
    struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(dev_handle->dev);
    IOReturn kresult;
    int i;
  
    if (dpriv->open_count == 0) {
      /* something is probably very wrong if this is the case */
      usbi_err (HANDLE_CTX (dev_handle), "Close called on a device that was not open!\n");
      return;
    }
  
    dpriv->open_count--;
  
    /* make sure all interfaces are released */
    for (i = 0 ; i < USB_MAXINTERFACES ; i++)
      if (dev_handle->claimed_interfaces & (1 << i))
        libusb_release_interface (dev_handle, i);
  
    if (0 == dpriv->open_count) {
      /* delete the device's async event source */
      if (priv->cfSource) {
        CFRunLoopRemoveSource (libusb_darwin_acfl, priv->cfSource, kCFRunLoopDefaultMode);
        CFRelease (priv->cfSource);
        priv->cfSource = NULL;
        CFRelease (libusb_darwin_acfl);
      }
  
      if (priv->is_open) {
        /* close the device */
        kresult = (*(dpriv->device))->USBDeviceClose(dpriv->device);
        if (kresult) {
          /* Log the fact that we had a problem closing the file, however failing a
           * close isn't really an error, so return success anyway */
          usbi_warn (HANDLE_CTX (dev_handle), "USBDeviceClose: %s", darwin_error_str(kresult));
        }
      }
    }
  
    /* file descriptors are maintained per-instance */
    usbi_remove_pollfd (HANDLE_CTX (dev_handle), priv->fds[0]);
    close (priv->fds[1]);
    close (priv->fds[0]);
  
    priv->fds[0] = priv->fds[1] = -1;
  }
  
  static int darwin_get_configuration(struct libusb_device_handle *dev_handle, int *config) {
    struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(dev_handle->dev);
  
    *config = (int) dpriv->active_config;
  
    return 0;
  }
  
  static int darwin_set_configuration(struct libusb_device_handle *dev_handle, int config) {
    struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(dev_handle->dev);
    IOReturn kresult;
    int i;
  
    /* Setting configuration will invalidate the interface, so we need
       to reclaim it. First, dispose of existing interfaces, if any. */
    for (i = 0 ; i < USB_MAXINTERFACES ; i++)
      if (dev_handle->claimed_interfaces & (1 << i))
        darwin_release_interface (dev_handle, i);
  
    kresult = (*(dpriv->device))->SetConfiguration (dpriv->device, config);
    if (kresult != kIOReturnSuccess)
      return darwin_to_libusb (kresult);
  
    /* Reclaim any interfaces. */
    for (i = 0 ; i < USB_MAXINTERFACES ; i++)
      if (dev_handle->claimed_interfaces & (1 << i))
        darwin_claim_interface (dev_handle, i);
  
    dpriv->active_config = config;
  
    return 0;
  }
  
  static int darwin_get_interface (usb_device_t **darwin_device, uint8_t ifc, io_service_t *usbInterfacep) {
    IOUSBFindInterfaceRequest request;
    kern_return_t             kresult;
    io_iterator_t             interface_iterator;
    UInt8                     bInterfaceNumber;
    int                       ret;
  
    *usbInterfacep = IO_OBJECT_NULL;
  
    /* Setup the Interface Request */
    request.bInterfaceClass    = kIOUSBFindInterfaceDontCare;
    request.bInterfaceSubClass = kIOUSBFindInterfaceDontCare;
    request.bInterfaceProtocol = kIOUSBFindInterfaceDontCare;
    request.bAlternateSetting  = kIOUSBFindInterfaceDontCare;
  
    kresult = (*(darwin_device))->CreateInterfaceIterator(darwin_device, &request, &interface_iterator);
    if (kresult)
      return kresult;
  
    while ((*usbInterfacep = IOIteratorNext(interface_iterator))) {
      /* find the interface number */
      ret = get_ioregistry_value_number (*usbInterfacep, CFSTR("bInterfaceNumber"), kCFNumberSInt8Type,
                                         &bInterfaceNumber);
  
      if (ret && bInterfaceNumber == ifc) {
        break;
      }
  
      (void) IOObjectRelease (*usbInterfacep);
    }
  
    /* done with the interface iterator */
    IOObjectRelease(interface_iterator);
  
    return 0;
  }
  
  static int get_endpoints (struct libusb_device_handle *dev_handle, int iface) {
    struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)dev_handle->os_priv;
  
    /* current interface */
    struct darwin_interface *cInterface = &priv->interfaces[iface];
  
    kern_return_t kresult;
  
    u_int8_t numep, direction, number;
    u_int8_t dont_care1, dont_care3;
    u_int16_t dont_care2;
    int i;
  
    usbi_dbg ("building table of endpoints.");
  
    /* retrieve the total number of endpoints on this interface */
    kresult = (*(cInterface->interface))->GetNumEndpoints(cInterface->interface, &numep);
    if (kresult) {
      usbi_err (HANDLE_CTX (dev_handle), "can't get number of endpoints for interface: %s", darwin_error_str(kresult));
      return darwin_to_libusb (kresult);
    }
  
    /* iterate through pipe references */
    for (i = 1 ; i <= numep ; i++) {
      kresult = (*(cInterface->interface))->GetPipeProperties(cInterface->interface, i, &direction, &number, &dont_care1,
                                                              &dont_care2, &dont_care3);
  
      if (kresult != kIOReturnSuccess) {
        usbi_err (HANDLE_CTX (dev_handle), "error getting pipe information for pipe %d: %s", i, darwin_error_str(kresult));
  
        return darwin_to_libusb (kresult);
      }
  
      usbi_dbg ("interface: %i pipe %i: dir: %i number: %i", iface, i, direction, number);
  
      cInterface->endpoint_addrs[i - 1] = ((direction << 7 & LIBUSB_ENDPOINT_DIR_MASK) | (number & LIBUSB_ENDPOINT_ADDRESS_MASK));
    }
  
    cInterface->num_endpoints = numep;
  
    return 0;
  }
  
  static int darwin_claim_interface(struct libusb_device_handle *dev_handle, int iface) {
    struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(dev_handle->dev);
    struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)dev_handle->os_priv;
    io_service_t          usbInterface = IO_OBJECT_NULL;
    IOReturn kresult;
    IOCFPlugInInterface **plugInInterface = NULL;
    SInt32                score;
  
    /* current interface */
    struct darwin_interface *cInterface = &priv->interfaces[iface];
  
    kresult = darwin_get_interface (dpriv->device, iface, &usbInterface);
    if (kresult != kIOReturnSuccess)
      return darwin_to_libusb (kresult);
  
    /* make sure we have an interface */
    if (!usbInterface && dpriv->first_config != 0) {
      usbi_info (HANDLE_CTX (dev_handle), "no interface found; setting configuration: %d", dpriv->first_config);
  
      /* set the configuration */
      kresult = darwin_set_configuration (dev_handle, dpriv->first_config);
      if (kresult != LIBUSB_SUCCESS) {
        usbi_err (HANDLE_CTX (dev_handle), "could not set configuration");
        return kresult;
      }
  
      kresult = darwin_get_interface (dpriv->device, iface, &usbInterface);
      if (kresult) {
        usbi_err (HANDLE_CTX (dev_handle), "darwin_get_interface: %s", darwin_error_str(kresult));
        return darwin_to_libusb (kresult);
      }
    }
  
    if (!usbInterface) {
      usbi_err (HANDLE_CTX (dev_handle), "interface not found");
      return LIBUSB_ERROR_NOT_FOUND;
    }
  
    /* get an interface to the device's interface */
    kresult = IOCreatePlugInInterfaceForService (usbInterface, kIOUSBInterfaceUserClientTypeID,
                                                 kIOCFPlugInInterfaceID, &plugInInterface, &score);
  
    /* ignore release error */
    (void)IOObjectRelease (usbInterface);
  
    if (kresult) {
      usbi_err (HANDLE_CTX (dev_handle), "IOCreatePlugInInterfaceForService: %s", darwin_error_str(kresult));
      return darwin_to_libusb (kresult);
    }
  
    if (!plugInInterface) {
      usbi_err (HANDLE_CTX (dev_handle), "plugin interface not found");
      return LIBUSB_ERROR_NOT_FOUND;
    }
  
    /* Do the actual claim */
    kresult = (*plugInInterface)->QueryInterface(plugInInterface,
                                                 CFUUIDGetUUIDBytes(kIOUSBInterfaceInterfaceID),
                                                 (LPVOID)&cInterface->interface);
    /* We no longer need the intermediate plug-in */
    /* Use release instead of IODestroyPlugInInterface to avoid stopping IOServices associated with this device */
    (*plugInInterface)->Release (plugInInterface);
    if (kresult || !cInterface->interface) {
      usbi_err (HANDLE_CTX (dev_handle), "QueryInterface: %s", darwin_error_str(kresult));
      return darwin_to_libusb (kresult);
    }
  
    /* claim the interface */
    kresult = (*(cInterface->interface))->USBInterfaceOpen(cInterface->interface);
    if (kresult) {
      usbi_err (HANDLE_CTX (dev_handle), "USBInterfaceOpen: %s", darwin_error_str(kresult));
      return darwin_to_libusb (kresult);
    }
  
    /* update list of endpoints */
    kresult = get_endpoints (dev_handle, iface);
    if (kresult) {
      /* this should not happen */
      darwin_release_interface (dev_handle, iface);
      usbi_err (HANDLE_CTX (dev_handle), "could not build endpoint table");
      return kresult;
    }
  
    cInterface->cfSource = NULL;
  
    /* create async event source */
    kresult = (*(cInterface->interface))->CreateInterfaceAsyncEventSource (cInterface->interface, &cInterface->cfSource);
    if (kresult != kIOReturnSuccess) {
      usbi_err (HANDLE_CTX (dev_handle), "could not create async event source");
  
      /* can't continue without an async event source */
      (void)darwin_release_interface (dev_handle, iface);
  
      return darwin_to_libusb (kresult);
    }
  
    /* add the cfSource to the async thread's run loop */
    CFRunLoopAddSource(libusb_darwin_acfl, cInterface->cfSource, kCFRunLoopDefaultMode);
  
    usbi_dbg ("interface opened");
  
    return 0;
  }
  
  static int darwin_release_interface(struct libusb_device_handle *dev_handle, int iface) {
    struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)dev_handle->os_priv;
    IOReturn kresult;
  
    /* current interface */
    struct darwin_interface *cInterface = &priv->interfaces[iface];
  
    /* Check to see if an interface is open */
    if (!cInterface->interface)
      return LIBUSB_SUCCESS;
  
    /* clean up endpoint data */
    cInterface->num_endpoints = 0;
  
    /* delete the interface's async event source */
    if (cInterface->cfSource) {
      CFRunLoopRemoveSource (libusb_darwin_acfl, cInterface->cfSource, kCFRunLoopDefaultMode);
      CFRelease (cInterface->cfSource);
    }
  
    kresult = (*(cInterface->interface))->USBInterfaceClose(cInterface->interface);
    if (kresult)
      usbi_warn (HANDLE_CTX (dev_handle), "USBInterfaceClose: %s", darwin_error_str(kresult));
  
    kresult = (*(cInterface->interface))->Release(cInterface->interface);
    if (kresult != kIOReturnSuccess)
      usbi_warn (HANDLE_CTX (dev_handle), "Release: %s", darwin_error_str(kresult));
  
    cInterface->interface = IO_OBJECT_NULL;
  
    return darwin_to_libusb (kresult);
  }
  
  static int darwin_set_interface_altsetting(struct libusb_device_handle *dev_handle, int iface, int altsetting) {
    struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)dev_handle->os_priv;
    IOReturn kresult;
  
    /* current interface */
    struct darwin_interface *cInterface = &priv->interfaces[iface];
  
    if (!cInterface->interface)
      return LIBUSB_ERROR_NO_DEVICE;
  
    kresult = (*(cInterface->interface))->SetAlternateInterface (cInterface->interface, altsetting);
    if (kresult != kIOReturnSuccess)
      darwin_reset_device (dev_handle);
  
    /* update list of endpoints */
    kresult = get_endpoints (dev_handle, iface);
    if (kresult) {
      /* this should not happen */
      darwin_release_interface (dev_handle, iface);
      usbi_err (HANDLE_CTX (dev_handle), "could not build endpoint table");
      return kresult;
    }
  
    return darwin_to_libusb (kresult);
  }
  
  static int darwin_clear_halt(struct libusb_device_handle *dev_handle, unsigned char endpoint) {
    struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)dev_handle->os_priv;
  
    /* current interface */
    struct darwin_interface *cInterface;
    uint8_t pipeRef, iface;
    IOReturn kresult;
  
    /* determine the interface/endpoint to use */
    if (ep_to_pipeRef (dev_handle, endpoint, &pipeRef, &iface) != 0) {
      usbi_err (HANDLE_CTX (dev_handle), "endpoint not found on any open interface");
  
      return LIBUSB_ERROR_NOT_FOUND;
    }
  
    cInterface = &priv->interfaces[iface];
  
    /* newer versions of darwin support clearing additional bits on the device's endpoint */
    kresult = (*(cInterface->interface))->ClearPipeStallBothEnds(cInterface->interface, pipeRef);
    if (kresult)
      usbi_warn (HANDLE_CTX (dev_handle), "ClearPipeStall: %s", darwin_error_str (kresult));
  
    return darwin_to_libusb (kresult);
  }
  
  static int darwin_reset_device(struct libusb_device_handle *dev_handle) {
    struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(dev_handle->dev);
    IOUSBDeviceDescriptor descriptor;
    IOUSBConfigurationDescriptorPtr cached_configuration;
    IOUSBConfigurationDescriptor configuration;
    bool reenumerate = false;
    IOReturn kresult;
    int i;
  
    kresult = (*(dpriv->device))->ResetDevice (dpriv->device);
    if (kresult) {
      usbi_err (HANDLE_CTX (dev_handle), "ResetDevice: %s", darwin_error_str (kresult));
      return darwin_to_libusb (kresult);
    }
  
    do {
      usbi_dbg ("darwin/reset_device: checking if device descriptor changed");
  
      /* ignore return code. if we can't get a descriptor it might be worthwhile re-enumerating anway */
      (void) darwin_request_descriptor (dpriv->device, kUSBDeviceDesc, 0, &descriptor, sizeof (descriptor));
  
      /* check if the device descriptor has changed */
      if (0 != memcmp (&dpriv->dev_descriptor, &descriptor, sizeof (descriptor))) {
        reenumerate = true;
        break;
      }
  
      /* check if any configuration descriptor has changed */
      for (i = 0 ; i < descriptor.bNumConfigurations ; ++i) {
        usbi_dbg ("darwin/reset_device: checking if configuration descriptor %d changed", i);
  
        (void) darwin_request_descriptor (dpriv->device, kUSBConfDesc, i, &configuration, sizeof (configuration));
        (*(dpriv->device))->GetConfigurationDescriptorPtr (dpriv->device, i, &cached_configuration);
  
        if (!cached_configuration || 0 != memcmp (cached_configuration, &configuration, sizeof (configuration))) {
          reenumerate = true;
          break;
        }
      }
    } while (0);
  
    if (reenumerate) {
      usbi_dbg ("darwin/reset_device: device requires reenumeration");
      (void) (*(dpriv->device))->USBDeviceReEnumerate (dpriv->device, 0);
      return LIBUSB_ERROR_NOT_FOUND;
    }
  
    usbi_dbg ("darwin/reset_device: device reset complete");
  
    return LIBUSB_SUCCESS;
  }
  
  static int darwin_kernel_driver_active(struct libusb_device_handle *dev_handle, int interface) {
    struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(dev_handle->dev);
    io_service_t usbInterface;
    CFTypeRef driver;
    IOReturn kresult;
  
    kresult = darwin_get_interface (dpriv->device, interface, &usbInterface);
    if (kresult) {
      usbi_err (HANDLE_CTX (dev_handle), "darwin_get_interface: %s", darwin_error_str(kresult));
  
      return darwin_to_libusb (kresult);
    }
  
    driver = IORegistryEntryCreateCFProperty (usbInterface, kIOBundleIdentifierKey, kCFAllocatorDefault, 0);
    IOObjectRelease (usbInterface);
  
    if (driver) {
      CFRelease (driver);
  
      return 1;
    }
  
    /* no driver */
    return 0;
  }
  
  /* attaching/detaching kernel drivers is not currently supported (maybe in the future?) */
  static int darwin_attach_kernel_driver (struct libusb_device_handle *dev_handle, int interface) {
    (void)dev_handle;
    (void)interface;
    return LIBUSB_ERROR_NOT_SUPPORTED;
  }
  
  static int darwin_detach_kernel_driver (struct libusb_device_handle *dev_handle, int interface) {
    (void)dev_handle;
    (void)interface;
    return LIBUSB_ERROR_NOT_SUPPORTED;
  }
  
  static void darwin_destroy_device(struct libusb_device *dev) {
    struct darwin_device_priv *dpriv = (struct darwin_device_priv *) dev->os_priv;
  
    if (dpriv->dev) {
      /* need to hold the lock in case this is the last reference to the device */
      usbi_mutex_lock(&darwin_cached_devices_lock);
      darwin_deref_cached_device (dpriv->dev);
      dpriv->dev = NULL;
      usbi_mutex_unlock(&darwin_cached_devices_lock);
    }
  }
  
  static int submit_bulk_transfer(struct usbi_transfer *itransfer) {
    struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
    struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)transfer->dev_handle->os_priv;
  
    IOReturn               ret;
    uint8_t                transferType;
    /* None of the values below are used in libusbx for bulk transfers */
    uint8_t                direction, number, interval, pipeRef, iface;
    uint16_t               maxPacketSize;
  
    struct darwin_interface *cInterface;
  
    if (ep_to_pipeRef (transfer->dev_handle, transfer->endpoint, &pipeRef, &iface) != 0) {
      usbi_err (TRANSFER_CTX (transfer), "endpoint not found on any open interface");
  
      return LIBUSB_ERROR_NOT_FOUND;
    }
  
    cInterface = &priv->interfaces[iface];
  
    ret = (*(cInterface->interface))->GetPipeProperties (cInterface->interface, pipeRef, &direction, &number,
                                                         &transferType, &maxPacketSize, &interval);
  
    if (ret) {
      usbi_err (TRANSFER_CTX (transfer), "bulk transfer failed (dir = %s): %s (code = 0x%08x)", IS_XFERIN(transfer) ? "In" : "Out",
                darwin_error_str(ret), ret);
      return darwin_to_libusb (ret);
    }
  
    if (0 != (transfer->length % maxPacketSize)) {
      /* do not need a zero packet */
      transfer->flags &= ~LIBUSB_TRANSFER_ADD_ZERO_PACKET;
    }
  
    /* submit the request */
    /* timeouts are unavailable on interrupt endpoints */
    if (transferType == kUSBInterrupt) {
      if (IS_XFERIN(transfer))
        ret = (*(cInterface->interface))->ReadPipeAsync(cInterface->interface, pipeRef, transfer->buffer,
                                                        transfer->length, darwin_async_io_callback, itransfer);
      else
        ret = (*(cInterface->interface))->WritePipeAsync(cInterface->interface, pipeRef, transfer->buffer,
                                                         transfer->length, darwin_async_io_callback, itransfer);
    } else {
      itransfer->flags |= USBI_TRANSFER_OS_HANDLES_TIMEOUT;
  
      if (IS_XFERIN(transfer))
        ret = (*(cInterface->interface))->ReadPipeAsyncTO(cInterface->interface, pipeRef, transfer->buffer,
                                                          transfer->length, transfer->timeout, transfer->timeout,
                                                          darwin_async_io_callback, (void *)itransfer);
      else
        ret = (*(cInterface->interface))->WritePipeAsyncTO(cInterface->interface, pipeRef, transfer->buffer,
                                                           transfer->length, transfer->timeout, transfer->timeout,
                                                           darwin_async_io_callback, (void *)itransfer);
    }
  
    if (ret)
      usbi_err (TRANSFER_CTX (transfer), "bulk transfer failed (dir = %s): %s (code = 0x%08x)", IS_XFERIN(transfer) ? "In" : "Out",
                 darwin_error_str(ret), ret);
  
    return darwin_to_libusb (ret);
  }
  
  static int submit_iso_transfer(struct usbi_transfer *itransfer) {
    struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
    struct darwin_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
    struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)transfer->dev_handle->os_priv;
  
    IOReturn kresult;
    uint8_t direction, number, interval, pipeRef, iface, transferType;
    uint16_t maxPacketSize;
    UInt64 frame;
    AbsoluteTime atTime;
    int i;
  
    struct darwin_interface *cInterface;
  
    /* construct an array of IOUSBIsocFrames, reuse the old one if possible */
    if (tpriv->isoc_framelist && tpriv->num_iso_packets != transfer->num_iso_packets) {
      free(tpriv->isoc_framelist);
      tpriv->isoc_framelist = NULL;
    }
  
    if (!tpriv->isoc_framelist) {
      tpriv->num_iso_packets = transfer->num_iso_packets;
      tpriv->isoc_framelist = (IOUSBIsocFrame*) calloc (transfer->num_iso_packets, sizeof(IOUSBIsocFrame));
      if (!tpriv->isoc_framelist)
        return LIBUSB_ERROR_NO_MEM;
    }
  
    /* copy the frame list from the libusbx descriptor (the structures differ only is member order) */
    for (i = 0 ; i < transfer->num_iso_packets ; i++)
      tpriv->isoc_framelist[i].frReqCount = transfer->iso_packet_desc[i].length;
  
    /* determine the interface/endpoint to use */
    if (ep_to_pipeRef (transfer->dev_handle, transfer->endpoint, &pipeRef, &iface) != 0) {
      usbi_err (TRANSFER_CTX (transfer), "endpoint not found on any open interface");
  
      return LIBUSB_ERROR_NOT_FOUND;
    }
  
    cInterface = &priv->interfaces[iface];
  
    /* determine the properties of this endpoint and the speed of the device */
    (*(cInterface->interface))->GetPipeProperties (cInterface->interface, pipeRef, &direction, &number,
                                                   &transferType, &maxPacketSize, &interval);
  
    /* Last but not least we need the bus frame number */
    kresult = (*(cInterface->interface))->GetBusFrameNumber(cInterface->interface, &frame, &atTime);
    if (kresult) {
      usbi_err (TRANSFER_CTX (transfer), "failed to get bus frame number: %d", kresult);
      free(tpriv->isoc_framelist);
      tpriv->isoc_framelist = NULL;
  
      return darwin_to_libusb (kresult);
    }
  
    (*(cInterface->interface))->GetPipeProperties (cInterface->interface, pipeRef, &direction, &number,
                                                   &transferType, &maxPacketSize, &interval);
  
    /* schedule for a frame a little in the future */
    frame += 4;
  
    if (cInterface->frames[transfer->endpoint] && frame < cInterface->frames[transfer->endpoint])
      frame = cInterface->frames[transfer->endpoint];
  
    /* submit the request */
    if (IS_XFERIN(transfer))
      kresult = (*(cInterface->interface))->ReadIsochPipeAsync(cInterface->interface, pipeRef, transfer->buffer, frame,
                                                               transfer->num_iso_packets, tpriv->isoc_framelist, darwin_async_io_callback,
                                                               itransfer);
    else
      kresult = (*(cInterface->interface))->WriteIsochPipeAsync(cInterface->interface, pipeRef, transfer->buffer, frame,
                                                                transfer->num_iso_packets, tpriv->isoc_framelist, darwin_async_io_callback,
                                                                itransfer);
  
    if (LIBUSB_SPEED_FULL == transfer->dev_handle->dev->speed)
      /* Full speed */
      cInterface->frames[transfer->endpoint] = frame + transfer->num_iso_packets * (1 << (interval - 1));
    else
      /* High/super speed */
      cInterface->frames[transfer->endpoint] = frame + transfer->num_iso_packets * (1 << (interval - 1)) / 8;
  
    if (kresult != kIOReturnSuccess) {
      usbi_err (TRANSFER_CTX (transfer), "isochronous transfer failed (dir: %s): %s", IS_XFERIN(transfer) ? "In" : "Out",
                 darwin_error_str(kresult));
      free (tpriv->isoc_framelist);
      tpriv->isoc_framelist = NULL;
    }
  
    return darwin_to_libusb (kresult);
  }
  
  static int submit_control_transfer(struct usbi_transfer *itransfer) {
    struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
    struct libusb_control_setup *setup = (struct libusb_control_setup *) transfer->buffer;
    struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(transfer->dev_handle->dev);
    struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)transfer->dev_handle->os_priv;
    struct darwin_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
  
    IOReturn               kresult;
  
    bzero(&tpriv->req, sizeof(tpriv->req));
  
    /* IOUSBDeviceInterface expects the request in cpu endianess */
    tpriv->req.bmRequestType     = setup->bmRequestType;
    tpriv->req.bRequest          = setup->bRequest;
    /* these values should be in bus order from libusb_fill_control_setup */
    tpriv->req.wValue            = OSSwapLittleToHostInt16 (setup->wValue);
    tpriv->req.wIndex            = OSSwapLittleToHostInt16 (setup->wIndex);
    tpriv->req.wLength           = OSSwapLittleToHostInt16 (setup->wLength);
    /* data is stored after the libusbx control block */
    tpriv->req.pData             = transfer->buffer + LIBUSB_CONTROL_SETUP_SIZE;
    tpriv->req.completionTimeout = transfer->timeout;
    tpriv->req.noDataTimeout     = transfer->timeout;
  
    itransfer->flags |= USBI_TRANSFER_OS_HANDLES_TIMEOUT;
  
    /* all transfers in libusb-1.0 are async */
  
    if (transfer->endpoint) {
      struct darwin_interface *cInterface;
      uint8_t                 pipeRef, iface;
  
      if (ep_to_pipeRef (transfer->dev_handle, transfer->endpoint, &pipeRef, &iface) != 0) {
        usbi_err (TRANSFER_CTX (transfer), "endpoint not found on any open interface");
  
        return LIBUSB_ERROR_NOT_FOUND;
      }
  
      cInterface = &priv->interfaces[iface];
  
      kresult = (*(cInterface->interface))->ControlRequestAsyncTO (cInterface->interface, pipeRef, &(tpriv->req), darwin_async_io_callback, itransfer);
    } else
      /* control request on endpoint 0 */
      kresult = (*(dpriv->device))->DeviceRequestAsyncTO(dpriv->device, &(tpriv->req), darwin_async_io_callback, itransfer);
  
    if (kresult != kIOReturnSuccess)
      usbi_err (TRANSFER_CTX (transfer), "control request failed: %s", darwin_error_str(kresult));
  
    return darwin_to_libusb (kresult);
  }
  
  static int darwin_submit_transfer(struct usbi_transfer *itransfer) {
    struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
  
    switch (transfer->type) {
    case LIBUSB_TRANSFER_TYPE_CONTROL:
      return submit_control_transfer(itransfer);
    case LIBUSB_TRANSFER_TYPE_BULK:
    case LIBUSB_TRANSFER_TYPE_INTERRUPT:
      return submit_bulk_transfer(itransfer);
    case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
      return submit_iso_transfer(itransfer);
    default:
      usbi_err (TRANSFER_CTX(transfer), "unknown endpoint type %d", transfer->type);
      return LIBUSB_ERROR_INVALID_PARAM;
    }
  }
  
  static int cancel_control_transfer(struct usbi_transfer *itransfer) {
    struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
    struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(transfer->dev_handle->dev);
    IOReturn kresult;
  
    usbi_warn (ITRANSFER_CTX (itransfer), "aborting all transactions control pipe");
  
    if (!dpriv->device)
      return LIBUSB_ERROR_NO_DEVICE;
  
    kresult = (*(dpriv->device))->USBDeviceAbortPipeZero (dpriv->device);
  
    return darwin_to_libusb (kresult);
  }
  
  static int darwin_abort_transfers (struct usbi_transfer *itransfer) {
    struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
    struct darwin_cached_device *dpriv = DARWIN_CACHED_DEVICE(transfer->dev_handle->dev);
    struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)transfer->dev_handle->os_priv;
    struct darwin_interface *cInterface;
    uint8_t pipeRef, iface;
    IOReturn kresult;
  
    if (ep_to_pipeRef (transfer->dev_handle, transfer->endpoint, &pipeRef, &iface) != 0) {
      usbi_err (TRANSFER_CTX (transfer), "endpoint not found on any open interface");
  
      return LIBUSB_ERROR_NOT_FOUND;
    }
  
    cInterface = &priv->interfaces[iface];
  
    if (!dpriv->device)
      return LIBUSB_ERROR_NO_DEVICE;
  
    usbi_warn (ITRANSFER_CTX (itransfer), "aborting all transactions on interface %d pipe %d", iface, pipeRef);
  
    /* abort transactions */
    (*(cInterface->interface))->AbortPipe (cInterface->interface, pipeRef);
  
    usbi_dbg ("calling clear pipe stall to clear the data toggle bit");
  
    /* newer versions of darwin support clearing additional bits on the device's endpoint */
    kresult = (*(cInterface->interface))->ClearPipeStallBothEnds(cInterface->interface, pipeRef);
  
    return darwin_to_libusb (kresult);
  }
  
  static int darwin_cancel_transfer(struct usbi_transfer *itransfer) {
    struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
  
    switch (transfer->type) {
    case LIBUSB_TRANSFER_TYPE_CONTROL:
      return cancel_control_transfer(itransfer);
    case LIBUSB_TRANSFER_TYPE_BULK:
    case LIBUSB_TRANSFER_TYPE_INTERRUPT:
    case LIBUSB_TRANSFER_TYPE_ISOCHRONOUS:
      return darwin_abort_transfers (itransfer);
    default:
      usbi_err (TRANSFER_CTX(transfer), "unknown endpoint type %d", transfer->type);
      return LIBUSB_ERROR_INVALID_PARAM;
    }
  }
  
  static void darwin_clear_transfer_priv (struct usbi_transfer *itransfer) {
    struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
    struct darwin_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
  
    if (transfer->type == LIBUSB_TRANSFER_TYPE_ISOCHRONOUS && tpriv->isoc_framelist) {
      free (tpriv->isoc_framelist);
      tpriv->isoc_framelist = NULL;
    }
  }
  
  static void darwin_async_io_callback (void *refcon, IOReturn result, void *arg0) {
    struct usbi_transfer *itransfer = (struct usbi_transfer *)refcon;
    struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
    struct darwin_device_handle_priv *priv = (struct darwin_device_handle_priv *)transfer->dev_handle->os_priv;
    struct darwin_msg_async_io_complete message = {.itransfer = itransfer, .result = result,
                                                   .size = (UInt32) (uintptr_t) arg0};
  
    usbi_dbg ("an async io operation has completed");
  
    /* if requested write a zero packet */
    if (kIOReturnSuccess == result && IS_XFEROUT(transfer) && transfer->flags & LIBUSB_TRANSFER_ADD_ZERO_PACKET) {
      struct darwin_interface *cInterface;
      uint8_t iface, pipeRef;
  
      (void) ep_to_pipeRef (transfer->dev_handle, transfer->endpoint, &pipeRef, &iface);
      cInterface = &priv->interfaces[iface];
  
      (*(cInterface->interface))->WritePipe (cInterface->interface, pipeRef, transfer->buffer, 0);
    }
  
    /* send a completion message to the device's file descriptor */
    write (priv->fds[1], &message, sizeof (message));
  }
  
  static int darwin_transfer_status (struct usbi_transfer *itransfer, kern_return_t result) {
    if (itransfer->flags & USBI_TRANSFER_TIMED_OUT)
      result = kIOUSBTransactionTimeout;
  
    switch (result) {
    case kIOReturnUnderrun:
    case kIOReturnSuccess:
      return LIBUSB_TRANSFER_COMPLETED;
    case kIOReturnAborted:
      return LIBUSB_TRANSFER_CANCELLED;
    case kIOUSBPipeStalled:
      usbi_dbg ("transfer error: pipe is stalled");
      return LIBUSB_TRANSFER_STALL;
    case kIOReturnOverrun:
      usbi_warn (ITRANSFER_CTX (itransfer), "transfer error: data overrun");
      return LIBUSB_TRANSFER_OVERFLOW;
    case kIOUSBTransactionTimeout:
      usbi_warn (ITRANSFER_CTX (itransfer), "transfer error: timed out");
      itransfer->flags |= USBI_TRANSFER_TIMED_OUT;
      return LIBUSB_TRANSFER_TIMED_OUT;
    default:
      usbi_warn (ITRANSFER_CTX (itransfer), "transfer error: %s (value = 0x%08x)", darwin_error_str (result), result);
      return LIBUSB_TRANSFER_ERROR;
    }
  }
  
  static void darwin_handle_callback (struct usbi_transfer *itransfer, kern_return_t result, UInt32 io_size) {
    struct libusb_transfer *transfer = USBI_TRANSFER_TO_LIBUSB_TRANSFER(itransfer);
    struct darwin_transfer_priv *tpriv = usbi_transfer_get_os_priv(itransfer);
    int isIsoc      = LIBUSB_TRANSFER_TYPE_ISOCHRONOUS == transfer->type;
    int isBulk      = LIBUSB_TRANSFER_TYPE_BULK == transfer->type;
    int isControl   = LIBUSB_TRANSFER_TYPE_CONTROL == transfer->type;
    int isInterrupt = LIBUSB_TRANSFER_TYPE_INTERRUPT == transfer->type;
    int i;
  
    if (!isIsoc && !isBulk && !isControl && !isInterrupt) {
      usbi_err (TRANSFER_CTX(transfer), "unknown endpoint type %d", transfer->type);
      return;
    }
  
    usbi_dbg ("handling %s completion with kernel status %d",
               isControl ? "control" : isBulk ? "bulk" : isIsoc ? "isoc" : "interrupt", result);
  
    if (kIOReturnSuccess == result || kIOReturnUnderrun == result) {
      if (isIsoc && tpriv->isoc_framelist) {
        /* copy isochronous results back */
  
        for (i = 0; i < transfer->num_iso_packets ; i++) {
          struct libusb_iso_packet_descriptor *lib_desc = &transfer->iso_packet_desc[i];
          lib_desc->status = darwin_to_libusb (tpriv->isoc_framelist[i].frStatus);
          lib_desc->actual_length = tpriv->isoc_framelist[i].frActCount;
        }
      } else if (!isIsoc)
        itransfer->transferred += io_size;
    }
  
    /* it is ok to handle cancelled transfers without calling usbi_handle_transfer_cancellation (we catch timeout transfers) */
    usbi_handle_transfer_completion (itransfer, darwin_transfer_status (itransfer, result));
  }
  
  static int op_handle_events(struct libusb_context *ctx, struct pollfd *fds, POLL_NFDS_TYPE nfds, int num_ready) {
    struct darwin_msg_async_io_complete message;
    POLL_NFDS_TYPE i = 0;
    ssize_t ret;
  
    usbi_mutex_lock(&ctx->open_devs_lock);
  
    for (i = 0; i < nfds && num_ready > 0; i++) {
      struct pollfd *pollfd = &fds[i];
  
      usbi_dbg ("checking fd %i with revents = %x", pollfd->fd, pollfd->revents);
  
      if (!pollfd->revents)
        continue;
  
      num_ready--;
  
      if (pollfd->revents & POLLERR) {
        /* this probably will never happen so ignore the error an move on. */
        continue;
      }
  
      /* there is only one type of message */
      ret = read (pollfd->fd, &message, sizeof (message));
      if (ret < (ssize_t) sizeof (message)) {
        usbi_dbg ("WARNING: short read on async io completion pipe\n");
        continue;
      }
  
      darwin_handle_callback (message.itransfer, message.result, message.size);
    }
  
    usbi_mutex_unlock(&ctx->open_devs_lock);
  
    return 0;
  }
  
  static int darwin_clock_gettime(int clk_id, struct timespec *tp) {
    mach_timespec_t sys_time;
    clock_serv_t clock_ref;
  
    switch (clk_id) {
    case USBI_CLOCK_REALTIME:
      /* CLOCK_REALTIME represents time since the epoch */
      clock_ref = clock_realtime;
      break;
    case USBI_CLOCK_MONOTONIC:
      /* use system boot time as reference for the monotonic clock */
      clock_ref = clock_monotonic;
      break;
    default:
      return LIBUSB_ERROR_INVALID_PARAM;
    }
  
    clock_get_time (clock_ref, &sys_time);
  
    tp->tv_sec  = sys_time.tv_sec;
    tp->tv_nsec = sys_time.tv_nsec;
  
    return 0;
  }
  
  const struct usbi_os_backend darwin_backend = {
          .name = "Darwin",
          .caps = 0,
          .init = darwin_init,
          .exit = darwin_exit,
          .get_device_list = NULL, /* not needed */
          .get_device_descriptor = darwin_get_device_descriptor,
          .get_active_config_descriptor = darwin_get_active_config_descriptor,
          .get_config_descriptor = darwin_get_config_descriptor,
  
          .open = darwin_open,
          .close = darwin_close,
          .get_configuration = darwin_get_configuration,
          .set_configuration = darwin_set_configuration,
          .claim_interface = darwin_claim_interface,
          .release_interface = darwin_release_interface,
  
          .set_interface_altsetting = darwin_set_interface_altsetting,
          .clear_halt = darwin_clear_halt,
          .reset_device = darwin_reset_device,
  
          .kernel_driver_active = darwin_kernel_driver_active,
          .detach_kernel_driver = darwin_detach_kernel_driver,
          .attach_kernel_driver = darwin_attach_kernel_driver,
  
          .destroy_device = darwin_destroy_device,
  
          .submit_transfer = darwin_submit_transfer,
          .cancel_transfer = darwin_cancel_transfer,
          .clear_transfer_priv = darwin_clear_transfer_priv,
  
          .handle_events = op_handle_events,
  
          .clock_gettime = darwin_clock_gettime,
  
          .device_priv_size = sizeof(struct darwin_device_priv),
          .device_handle_priv_size = sizeof(struct darwin_device_handle_priv),
          .transfer_priv_size = sizeof(struct darwin_transfer_priv),
          .add_iso_packet_size = 0,
  };
  