macOS下如何查找串口的父USB设备？

Question

以下是我尝试枚举 Mac 上找到的所有串行端口并遍历设备节点树以找到 USB 串行适配器的父 USB 设备的方法：

#import <Foundation/Foundation.h>
#import <IOKit/IOKitLib.h>
#import <IOKit/serial/IOSerialKeys.h>
#import <IOKit/usb/IOUSBLib.h>

int main(int argc, const char * argv[])
{
    @autoreleasepool
    {
        CFMutableDictionaryRef keywordDict = IOServiceMatching(kIOSerialBSDServiceValue);
        io_object_t port = 0;
        io_iterator_t iterator = 0;
        kern_return_t result = IOServiceGetMatchingServices(kIOMasterPortDefault, keywordDict, &iterator);
        if (result)
        {
            NSLog(@"Failed to find any serial ports.");
            exit(EXIT_FAILURE);
        }

        while ((port = IOIteratorNext(iterator)))
        {
            @autoreleasepool
            {
                NSMutableArray<NSDictionary *> *array = [NSMutableArray array];
                CFMutableDictionaryRef dict = NULL;
                result = IORegistryEntryCreateCFProperties(port, &dict, kCFAllocatorDefault, 0);
                if (!result)
                    [array addObject:CFBridgingRelease(dict)];

                io_object_t parent = 0;
                io_object_t parents = port;
                while (IORegistryEntryGetParentEntry(parents, kIOServicePlane, &parent))
                {
                    result = IORegistryEntryCreateCFProperties(parent, &dict, kCFAllocatorDefault, 0);
                    if (!result)
                        [array addObject:CFBridgingRelease(dict)];

                    if (parents != port)
                        IOObjectRelease(parents);
                    parents = parent;
                }

                NSLog(@"0x%08lx = %@", (uintptr_t)port, array);
            }
        }
    }
    return 0;
}

但是，虽然此代码可以找到所有串行端口（USB 串行适配器和我的 Hackintosh 上的 Super IO 端口），但向上遍历 IOService 树并不起作用。帮助？目标操作系统为 macOS 10.13.6。

编辑

这是我的一个 USB 串行适配器的输出：

2018-08-18 19:05:39.860794+0800 lstty[98738:5197725] 0x00002a07 = (
        {
        CFBundleIdentifier = "com.apple.iokit.IOSerialFamily";
        IOCalloutDevice = "/dev/cu.usbmodem1751";
        IOClass = IOSerialBSDClient;
        IODialinDevice = "/dev/tty.usbmodem1751";
        IOGeneralInterest = "IOCommand is not serializable";
        IOMatchCategory = IODefaultMatchCategory;
        IOProbeScore = 1000;
        IOProviderClass = IOSerialStreamSync;
        IOResourceMatch = IOBSD;
        IOSerialBSDClientType = IOModemSerialStream;
        IOTTYBaseName = usbmodem;
        IOTTYDevice = usbmodem1751;
        IOTTYSuffix = 1751;
    }
)

这是同一设备的ioreg -itrc IOSerialBSDClient -w0 输出：

+-o Root  <class IORegistryEntry, id 0x100000100, retain 15>
  +-o iMac14,2  <class IORegistryEntry:IOService:IOPlatformExpertDevice, id 0x100000110, registered, matched, active, busy 0 (51894 ms), retain 45>
    +-o AppleACPIPlatformExpert  <class IORegistryEntry:IOService:IOPlatformExpert:IODTPlatformExpert:IOACPIPlatformExpert:AppleACPIPlatformExpert, id 0x100000111, registered, matched, active, busy 0 (41509 ms), retain 50>
      +-o PCI0@0  <class IORegistryEntry:IOService:IOPlatformDevice:IOACPIPlatformDevice, id 0x10000013e, registered, matched, active, busy 0 (41377 ms), retain 54>
        +-o AppleACPIPCI  <class IORegistryEntry:IOService:IOPCIBridge:AppleACPIPCI, id 0x100000216, registered, matched, active, busy 0 (41332 ms), retain 31>
          +-o XHC@14  <class IORegistryEntry:IOService:IOPCIDevice, id 0x1000001f0, registered, matched, active, busy 0 (35582 ms), retain 11>
            +-o XHC@14000000  <class IORegistryEntry:IOService:AppleUSBHostController:AppleUSBXHCI:AppleUSBXHCIPCI:AppleUSBXHCILPT:AppleUSBXHCILPTH:AppleUSBXHCILPTHB, id 0x10000023d, registered, matched, active, busy 0 (35072 ms), retain 1249>
              +-o HS10@14a00000  <class IORegistryEntry:IOService:AppleUSBHostPort:AppleUSBXHCIPort:AppleUSB20XHCIPort, id 0x100000277, registered, matched, active, busy 0 (22180 ms), retain 17>
                +-o IOUSBHostDevice@14a00000  <class IORegistryEntry:IOService:IOUSBNub:IOUSBDevice, id 0x100007a40, registered, matched, active, busy 0 (1604 ms), retain 31>
                  +-o AppleUSB20Hub@14a00000  <class IORegistryEntry:IOService:AppleUSBHub:AppleUSB20Hub, id 0x100007a4e, registered, matched, active, busy 0 (1600 ms), retain 23>
                    +-o AppleUSB20HubPort@14a10000  <class IORegistryEntry:IOService:AppleUSBHostPort:AppleUSBHubPort:AppleUSB20HubPort, id 0x100007a52, registered, matched, active, busy 0 (964 ms), retain 17>
                      +-o IOUSBHostDevice@14a10000  <class IORegistryEntry:IOService:IOUSBNub:IOUSBDevice, id 0x1000082bb, registered, matched, active, busy 0 (323 ms), retain 32>
                        +-o AppleUSB20Hub@14a10000  <class IORegistryEntry:IOService:AppleUSBHub:AppleUSB20Hub, id 0x1000082d4, registered, matched, active, busy 0 (316 ms), retain 23>
                          +-o AppleUSB20HubPort@14a12000  <class IORegistryEntry:IOService:AppleUSBHostPort:AppleUSBHubPort:AppleUSB20HubPort, id 0x1000082d8, registered, matched, active, busy 0 (269 ms), retain 17>
                            +-o ComboDebug USB Serial@14a12000  <class IORegistryEntry:IOService:IOUSBNub:IOUSBDevice, id 0x10000837e, registered, matched, active, busy 0 (268 ms), retain 28>
                              +-o IOUSBHostInterface@1  <class IORegistryEntry:IOService:IOUSBNub:IOUSBInterface, id 0x100008390, registered, matched, active, busy 0 (259 ms), retain 8>
                                +-o AppleUSBACMData  <class IORegistryEntry:IOService:IOSerialDriverSync:AppleUSBACMData, id 0x1000083a0, registered, matched, active, busy 0 (1 ms), retain 6>
                                  +-o IOModemSerialStreamSync  <class IORegistryEntry:IOService:IOSerialStreamSync:IOModemSerialStreamSync, id 0x100008417, registered, matched, active, busy 0 (1 ms), retain 6>
                                    +-o IOSerialBSDClient  <class IORegistryEntry:IOService:IOSerialBSDClient, id 0x100008418, registered, matched, active, busy 0 (0 ms), retain 5>
                                        {
                                          "IOClass" = "IOSerialBSDClient"
                                          "CFBundleIdentifier" = "com.apple.iokit.IOSerialFamily"
                                          "IOProviderClass" = "IOSerialStreamSync"
                                          "IOTTYBaseName" = "usbmodem"
                                          "IOSerialBSDClientType" = "IOModemSerialStream"
                                          "IOProbeScore" = 1000
                                          "IOCalloutDevice" = "/dev/cu.usbmodem1751"
                                          "IODialinDevice" = "/dev/tty.usbmodem1751"
                                          "IOMatchCategory" = "IODefaultMatchCategory"
                                          "IOTTYDevice" = "usbmodem1751"
                                          "IOResourceMatch" = "IOBSD"
                                          "IOGeneralInterest" = "IOCommand is not serializable"
                                          "IOTTYSuffix" = "1751"
                                        }

Answer 1

提前终止的问题是循环的退出条件：

     while (IORegistryEntryGetParentEntry(parents, kIOServicePlane, &parent))

IORegistryEntryGetParentEntry() 返回 kern_return_t - KERN_SUCCESS 为 0，因此这意味着 while 条件的计算结果为 false，并且循环永远不会运行。试试

     while (KERN_SUCCESS == IORegistryEntryGetParentEntry(parents, kIOServicePlane, &parent))