We implemented communication between Swift App and DriverKit driver using IOConnectCallAsyncStructMethod. So in Swift App we have following code to setup AsyncDataCallback: func AsyncDataCallback(refcon: UnsafeMutableRawPointer?, result: IOReturn, args: UnsafeMutablePointer<UnsafeMutableRawPointer?>?, numArgs: UInt32) -> Void { // handle args } var asyncRef: [io_user_reference_t] = .init(repeating: 0, count: 8) asyncRef[kIOAsyncCalloutFuncIndex] = unsafeBitCast(AsyncDataCallback as IOAsyncCallback, to: UInt64.self) asyncRef[kIOAsyncCalloutRefconIndex] = unsafeBitCast(self, to: UInt64.self) ...... let notificationPort = IONotificationPortCreate(kIOMasterPortDefault) let machNotificationPort = IONotificationPortGetMachPort(notificationPort) let runLoopSource = IONotificationPortGetRunLoopSource(notificationPort)! CFRunLoopAddSource(CFRunLoopGetCurrent(), runLoopSource.takeUnretainedValue(), CFRunLoopMode.defaultMode) var input = "someinput".map { UInt8($0.asciiValue!) } let inputSize = input.count IOConnectCallAsyncStructMethod(             connection,             123,             machNotificationPort,             &asyncRef,             UInt32(kIOAsyncCalloutCount),             &input,             inputSize,             nil,             nil ) In the driver's ExternalMethod we save callback in ivars: ivars->callbackAction = arguments->completion; ivars->callbackAction->retain(); Next we start communication with our device in a separate thread and execute callback when we get data from device: SendDataAsync(void *data, uint32_t dataLength) { const int asyncDataCount = 16; if (ivars->callbackAction != nullptr) {         Log("SendDataAsync() - got %u bytes", dataLength);         uint64_t asyncData[asyncDataCount] = { };         asyncData[0] = dataLength;         memcpy(asyncData + 1, data, dataLength);         AsyncCompletion(ivars->callbackAction, kIOReturnSuccess, asyncData, asyncDataCount);     } Limitation 1: Our device produces data packet every 10 ms. So driver gets 100 data packets per second. Receive rate is good and we verified it by logs. However we see some delay in AsyncCallback in Swift App. It looks like async calls are queued since we see that Swift App gets callbacks for a few seconds when we stopped to send data from Driver. We measured receive rate in Swift App and it is about 50 data packets per second. So what's a minimum call rate for AsyncCompletion? Is it higher than 10 ms? Maybe there is other more efficient way to asynchronously pass data from Driver to Swift App? Limitation 2: We thought we can buffer data packets and decrease AsyncCompletion call rate. However asyncData could be only 16 of uint64_t by declaration typedef uint64_t IOUserClientAsyncArgumentsArray[16];. Size of our data packer is 112 bytes that perfectly fits to max args size(8*16 = 128 bytes). So we can't cache and send 2 data packets. How we can avoid this limitation and send more data via AsyncCompletion? Is there any other API for asynchronous communication that allows send more data back?

According to Communicating Between a DriverKit Extension and a Client App we can use IOConnectCallScalarMethod to send/get data to Driver. We use unchecked variation of IOConnectCallScalarMethod to call method in our Driver from Client App. In a Driver's method we set arguments->scalarOutputCount greater than 16. However in a Client app outputCount equal to 16, so we can get only a portion of output. Is 16 limit enforced by IOConnectCallScalarMethod implementation? How we can get more than 16? Should we use IOConnectCallStructMethod instead?

We followed WWDC Session: System Extensions and DriverKit and recreated a code to do USB device communication via IOUSBHostPipe: struct MyDriver_IVars {     IOUSBHostInterface       *interface;     IOUSBHostPipe            *inPipe;     OSAction                 *ioCompleteCallback;     IOBufferMemoryDescriptor *inData;     uint16_t                  maxPacketSize; }; kern_return_t IMPL(MyDriver, Start) { ...     ivars->maxPacketSize = 64;     ret = ivars->interface->CreateIOBuffer( kIOMemoryDirectionInOut,                                            ivars->maxPacketSize,                                            &ivars->inData);     ret = CreateActionReadComplete(0, &ivars->ioCompleteCallback); ret = ivars->inPipe->AsyncIO(ivars->inData,                                  ivars->maxPacketSize,                                  ivars->ioCompleteCallback,                                  0); ... } Our Driver is started by OS when device is connected. We see that ReadComplete callback is called: void IMPL(MyDriver, ReadComplete) {     Log("ReadComplete() - status - %d; bytes count - %d", status, actualByteCount); } However it's not obvious how to read data received in this callback. I suspect that we should use IOBufferMemoryDescriptor *inData but we didn't find any good example/sample and documentation is poor. Our callback is called only once. It's not clear how to read a series of data from device? Should we create some loop and call inPipe->AsyncIO from callback? Also it would be helpful to see how to pass data to device. I hope we should fill IOBufferMemoryDescriptor *inData.

We requested com.apple.developer.driverkit.transport.usb entitlement a few days ago and it looks like it was granted since we see(can select) it at: App Id -> Additional Capabilities Tab -> DriverKit USB Transport - Vendor ID. We tried to choose both options at Additional Entitlements page Default and Driver Kit and System Extension Template for **** Mac Dev. Generated profile displays DriverKit USB Transport - Vendor ID in Enabled Capabilities in browser. However downloaded profile doesn't include com.apple.developer.driverkit.transport.usb. As a result our Driver fails to start and in Console we see: Driver: Unsatisfied entitlements: com.apple.developer.driverkit.transport.usb /Library/SystemExtensions/675FA894-8985-4D86-B0FF-B892B9AEA27B/Driver.dext/Driver signature not valid: -67671 BTW, we tried to modify existing profile and create a new one. Did we miss something? Is any way to check entitlement status with Apple support?

We inspired by announce that DriverKit will come to iPadOs this fall and decided to experiment with DriverKit on macOS. We started from scratch but followed all the recommendations from Sample. With our installer code we can: Install driver extension to macOS system. (systemextensionsctl list shows [activated enabled]) for our driver See driver record using ioreg. So it's displayed: MyDriver <class IOUserService, id 0x10000193b, registered, matched, active, busy 0 (0 ms), retain 7> See *.MyDriver process in Activity Monitor In client code we can find a match: private let dextIdentifier = "MyDriver" private var lastResult: kern_return_t = kIOReturnSuccess private var connection: io_connect_t = IO_OBJECT_NULL var iterator: io_iterator_t = IO_OBJECT_NULL var driver: io_service_t = IO_OBJECT_NULL lastResult = IOServiceGetMatchingServices(kIOMasterPortDefault, IOServiceNameMatching(dextIdentifier), &iterator) print("Search for services ...") while case let service = IOIteratorNext(iterator), service != IO_OBJECT_NULL { driver = service } IOObjectRelease(iterator) guard driver != IO_OBJECT_NULL else { return } So driver is not IO_OBJECT_NULL. But we stuck on IOServiceOpen. So code: lastResult = IOServiceOpen(driver, mach_task_self_, UInt32(kIOHIDServerConnectType), &connection); validateLastResult(forOperation: "opening service") prints opening service: (iokit/common) general error since IOServiceOpen returns 0x2bc What we tried: Disable SIP in recovery mode and set systemextensionsctl developer on Result: opening service: (iokit/common) general error Add com.apple.developer.driverkit.userclient-access to our client App. Result: App crashes on start and in Console we see: taskgated-helper - Unsatisfied entitlements: com.apple.developer.driverkit.userclient-access. We requested this entitlement. We found post were com.apple.developer.driverkit.allow-any-userclient-access suggested as solution. Result: Driver extension is not started and we see in Console: taskgated-helper MyDriver: Unsatisfied entitlements: com.apple.developer.driverkit.allow-any-userclient-access amfid /Library/SystemExtensions/B7624EEF-3688-4735-A58B-26FEF4DE353C/MyDriver.dext/MyDriver signature not valid: -67671 We recreated appIds, profiles on developer account that has com.apple.developer.driverkit.allow-any-userclient-access from Apple. Result: Driver extension is started but we still see opening service: (iokit/common) general error We modified CommunicatingBetweenADriverKitExtensionAndAClientApp.zip by setting our appIds and profiles and run in in SIP disabled mode. Result: opening service: (iokit/common) general error Our environment: macOS Monterey 12.4 XCode Version 13.4 (13F17a) Driver Code is pretty straightforward: ///// iig class MyDriver: public IOUserClient { public: virtual bool init(void) override; virtual kern_return_t Start(IOService * provider) override; virtual kern_return_t Stop(IOService* provider) override; virtual void free(void) override; }; ///// cpp #define Log(fmt, ...) os_log(OS_LOG_DEFAULT, "MyDriver - " fmt "\n", ##__VA_ARGS__) struct MyDriver_IVars { OSAction* callbackAction = nullptr; }; bool MyDriver::init() { bool result = false; Log("init()"); result = super::init(); if (result != true) { Log("init() - super::init failed."); goto Exit; } ivars = IONewZero(MyDriver_IVars, 1); if (ivars == nullptr) { Log("init() - Failed to allocate memory for ivars."); goto Exit; } Log("init() - Finished."); return true; Exit: return false; } kern_return_t IMPL(MyDriver, Start) { kern_return_t ret; ret = Start(provider, SUPERDISPATCH); if(ret != kIOReturnSuccess) { Log("Start() - super::Start failed with error: 0x%08x.", ret); goto Exit; } ret = RegisterService(); if (ret != kIOReturnSuccess) { Log("Start() - Failed to register service with error: 0x%08x.", ret); goto Exit; } Log("Start() - Finished."); ret = kIOReturnSuccess; Exit: return ret; } kern_return_t IMPL(MyDriver, Stop) { kern_return_t ret = kIOReturnSuccess; Log("Stop()"); ret = Stop(provider, SUPERDISPATCH); if (ret != kIOReturnSuccess) { Log("Stop() - super::Stop failed with error: 0x%08x.", ret); } return ret; } void MyDriver::free(void) { Log("free()"); IOSafeDeleteNULL(ivars, MyDriver_IVars, 1); super::free(); }

We updated our CI machine to: macOS Monterey Version 12.0.1 Xcode Version 13.1 (13A1030d) We started to receive UITest failures with following error: Testing failed: MemoryLeaksUITests: MemoryLeaksUITests-Runner (3507) encountered an error (The test runner failed to initialize for UI testing. If you believe this error represents a bug, please attach the result bundle at /Users/dev/Library/Developer/Xcode/DerivedData/MemoryLeaks-dduvihbyiuzwdnawggthtfwdgwks/Logs/Test/Test-MemoryLeaks-2021.11.05_13-43-58-+0300.xcresult. (Underlying Error: Timed out while enabling automation mode.)) The failure disappears if we enable UIAutomation for testmanagerd by providing password However it's not one time action. This permission dialog still appears after some time during a day. We noticed it constantly appears after machine reboot. Unfortunately it blocks us from using our CI machine as test runner. There is no option(checkbox) to permanently enable(provide password) automation in this dialog. Also it's not possible to add it in Settings -> Security & Privacy -> Privacy - Automation. Here is a sample project on GitHub to reproduce the issue. Steps: Reboot machine Run in terminal xcodebuild -target MemoryLeaksUITests -scheme MemoryLeaks test

We were encourage by Frameworks Engineer reply and Apple's Official Docs and started to use this approach in our App. But next we detected that App has leaked objects when we do Memory Graph Check in UITests. Removing of .accessibilityElement(children: .contain) solves the issue but we still want to use container identifiers in our UITests. Here is a sample project to illustrated and reproduce the issue: https://github.com/yuri-qualtie/MemoryLeaks. All the details and steps are described in Readme We need help with fix for .accessibilityElement(children: .contain) but any workaround is welcomed

We have SwiftUI Alert with destructive button - "Yes, sign out"? Alert( title: Text("Are you sure you want to sign out?"), message: Text("Some message"), primaryButton: .cancel( Text("No, don’t sign out") ), secondaryButton: .destructive( Text("Yes, sign out"), action: { print("signOut") } ) ) Button's text is displayed in pale pink but according to our design we want to change it to dark red. As an option we want change button's color as well. How we can accomplish it? As a side note: we found that for iOS we probably can utilise UIView.appearance(whenContainedInInstancesOf: API but it's available only on iOS but we are interested in solution for macOS

Code block below produces different results depending on if print is commented or not: import Combine var cancellables = SetAnyCancellable() enum FruitError: Error { case bad } var fruit = "apple" func getFruit() - String { fruit } Just(getFruit) //.print() .map{$0()} .flatMap { value - AnyPublisherString, FruitError in print("in flat map \(value)") if value == "apple" { fruit = "pineapple" return Fail(error: FruitError.bad).eraseToAnyPublisher() } return Just("banana").setFailureType(to: FruitError.self).eraseToAnyPublisher() } .retry(1) .sink(receiveCompletion: { print($0) }, receiveValue: {print($0)}) .store(in: &amp;cancellables) Without print: in flat map apple in flat map apple failure With print: in flat map apple in flat map pineapple banana receive finished finished receive finished Why does print or any other debug operator(breakpoint or handleEvent) change behaviour of sequence? Playground without print - https://developer.apple.com/forums/content/attachment/d8a1d043-191b-41f3-8f0e-72dafa621374 Playground with print - https://developer.apple.com/forums/content/attachment/7c0de4c2-37fb-4136-ae8e-5ed0e77287c5