c++ - 如何创建 IOUSBHostPipe::CompleteAsyncIO 回调？

Question

我正在编写一个 SystemExtension 来与 USB 设备通信。我最初的计划是创建一个Transfer分配必要的IOMemoryDe​​scriptor的类，然后传递我希望Transfer该类与之通信的接口。我希望将AsyncIO完成后产生的回调发送给班级。如果我需要将多个读取排队，我可以创建更多此类的实例。在回调中，我将解包数据，然后提交另一个read。TransfercompleteCallback

我Transfer用OSTypeAlloc(Transfer).

我面临的问题是创建 OSAction 失败并出现此堆栈跟踪：

0   libsystem_kernel.dylib          0x000000010df950ce __pthread_kill + 10
1   libsystem_pthread.dylib         0x000000010e07cf6a pthread_kill + 152
2   libsystem_c.dylib               0x000000010df2c3a0 abort + 120
3   com.apple.DriverKit             0x000000010dc9124b __assert_rtn + 102
4   com.apple.DriverKit             0x000000010dc91a34 OSCopyOutObjects(IOUserServer_IVars*, IORPCMessageMach*, IORPCMessage*, bool) (.cold.4) + 35
5   com.apple.DriverKit             0x000000010dc7a2ff OSCopyOutObjects(IOUserServer_IVars*, IORPCMessageMach*, IORPCMessage*, bool) + 328
6   com.apple.DriverKit             0x000000010dc79126 InvokeRemote(IOUserServer_IVars*, unsigned long long, IORPC) + 159
7   com.apple.DriverKit             0x000000010dc796b6 OSMetaClassBase::Invoke(IORPC) + 754
8   com.apple.DriverKit             0x000000010dc90048 OSAction::Create_Call(OSObject*, unsigned long long, unsigned long long, unsigned long, OSAction**) + 212
9   com.apple.DriverKit             0x000000010dc7ca15 OSAction::Create(OSObject*, unsigned long long, unsigned long long, unsigned long, OSAction**) + 37
10  sc.example.MyUserUSBInterfaceDriver 0x000000010dc3bffc Transfer::CreateActioncompleteCallback(unsigned long, OSAction**) + 60 (Transfer.iig.cpp:175)
11  sc.example.MyUserUSBInterfaceDriver 0x000000010dc34e6e Transfer::setup(IOUSBHostInterface*, int, int) + 638 (Transfer.cpp:53)

如果我改为在连接 USB 设备时由系统实例化的类中定义、实现和创建回调（该类在 plist 中使用 key 指定IOUserClass），则创建OSAction对象可以正常工作。

调用IOUSBHostInterface::Open是IOUserClass通过将指向 的指针IOUserClass作为第一个参数传递给Open. 这样做应该可以吗？或者是否要求该IOService对象也是从AsyncIO.

class Transfer : public OSObject {
public:
  bool init() override;
  void free() override;

  bool setup(IOUSBHostInterface* interface, int endpointAddress, int maxPacketSize) LOCALONLY;
  bool submit() LOCALONLY;

protected:
   virtual void completeCallback(OSAction* action,
                        IOReturn status,
                        uint32_t actualByteCount,
                        uint64_t completionTimestamp) TYPE(IOUSBHostPipe::CompleteAsyncIO);
};

struct Transfer_IVars {
  IOUSBHostInterface* interface;
  int maxPacketSize;
  IOUSBHostPipe* pipe;
  IOBufferMemoryDescriptor* buffer;
  OSAction* ioCompleteCallback;
};

bool Transfer::init() {
  LOG_DEBUG();
  if (!super::init()) {
    LOG_ERROR("super::init failed");
  }

  if (ivars = IONewZero(Transfer_IVars, 1); ivars == nullptr) {
    LOG_ERROR("Allocating ivars failed");
    return false;
  }

  return true;
}

void Transfer::free() {
  LOG_DEBUG();
  IOSafeDeleteNULL(ivars, Transfer_IVars, 1);
  super::free();
}

bool Transfer::setup(IOUSBHostInterface* interface, int endpointAddress,
                     int maxPacketSize) {
  ivars->interface = interface;
  ivars->maxPacketSize = maxPacketSize;

  if (auto ret = interface->CopyPipe(endpointAddress, &ivars->pipe);
      ret != kIOReturnSuccess) {
    LOG_ERROR("Could not copy pipe: %{public}s, endpointAddress: %{public}d",
              kern_return_t_toCStr(ret), endpointAddress);
  }

  if (auto ret =
        interface->CreateIOBuffer(kIOMemoryDirectionIn, maxPacketSize, &ivars->buffer);
      ret != kIOReturnSuccess) {
    LOG_ERROR("CreateIOBuffer failed, ret: %{public}d", ret);
    return false;
  }

  if (auto ret = CreateActioncompleteCallback(0, &ivars->ioCompleteCallback);
      ret != kIOReturnSuccess) {
    LOG_ERROR("Failed to set iocomplete callback, ret: %{public}d", ret);
    return false;
  }
  return true;
}

bool Transfer::submit() {
  if (auto ret = ivars->pipe->AsyncIO(ivars->buffer, ivars->maxPacketSize,
                                      ivars->ioCompleteCallback, 0);
      ret != kIOReturnSuccess) {
    LOG_ERROR("Failed to call AsyncIO, ret: %{public}d", ret);
    return false;
  }
  return true;
}

void IMPL(Transfer, completeCallback) {
  LOG_DEBUG(
    "Complete callback bytecount %{public}d, timestamp: %{public}llu, status %{public}s",
    actualByteCount, completionTimestamp, kern_return_t_toCStr(status));
// TODO Unpack and then schedule another read.
}

Answer 1