Detecting a generic Joystick on MacOS and receiving its reports

macos-usb-hidmanager.m

//with thanks to https://www.programmersought.com/article/3482617526/
// also see
//https://nachtimwald.com/2020/12/06/macos-usb-enumeration-in-c/
//https://developer.apple.com/library/archive/documentation/DeviceDrivers/Conceptual/USBBook/USBDeviceInterfaces/USBDevInterfaces.html

// actually, it'd be much quicker just to use https://github.com/libusb/hidapi

#import <Foundation/Foundation.h>
#include <IOKit/hid/IOHIDManager.h>

static IOHIDManagerRef hidManagerRef;


static void MyInputCallback(void* context, IOReturn result, void* sender, IOHIDReportType type, uint32_t reportID, uint8_t *report, CFIndex reportLength) {

    static uint8_t previous[64];

    // only process if changed
    if (memcmp(previous, report, reportLength) != 0){
    
        // note: unless we know how to interprete the data, this is pretty meaningless.
        // and for this we need access to the report descriptor, also see
        // https://github.com/libusb/hidapi (the descriptor is passed to get_usage() in the enumerator)
        // https://eleccelerator.com/usbdescreqparser/
        // get the IORegistryExplorer and you'll see that the descriptor is present in the ioreg, thus it might be smarter to
        // use ioreg services (see reference on top for Apple example)
    
        memcpy(previous, report, reportLength);
        printf("type = %d, %d =", type, reportLength);
        for (int i = 0; i < reportLength; i++){
            printf(" %02x", report[i]);
        }
        printf("\n");
    }
}
static void MyInputValueCallback(void * context, IOReturn result, void * sender, IOHIDValueRef value)
{
    IOHIDElementRef element = IOHIDValueGetElement(value);
    uint32_t usage = IOHIDElementGetUsage(element);
    printf("value changed: %02x %d\n", usage, IOHIDValueGetIntegerValue(value));
}

static void MyMultipltInputValueCallback(void * context,IOReturn result, void * sender, CFDictionaryRef multiple)
{
    NSLog(@"%s", multiple);
}

static void Handle_DeviceMatchingCallback(void *inContext,IOReturn inResult,void *inSender,IOHIDDeviceRef inIOHIDDeviceRef) {
    NSLog(@"insert: %p", (void *)inIOHIDDeviceRef);
    IOOptionBits options = 0;
    IOReturn ret = IOHIDDeviceOpen(inIOHIDDeviceRef,options);
    if (ret == kIOReturnSuccess) {
        NSLog(@"open success");
        uint8_t buf[64];

        // raw report
        IOHIDDeviceRegisterInputReportCallback(inIOHIDDeviceRef, buf, sizeof(buf), MyInputCallback, NULL);

        IOHIDDeviceRegisterInputValueCallback(inIOHIDDeviceRef, MyInputValueCallback, NULL);


//        CFDictionaryRef multiple = CFDictionaryCreate(<#CFAllocatorRef allocator#>, <#const void * * keys#>, <#const void * * values#>, <#CFIndex numValues#>, <#const CFDictionaryKeyCallBacks * keyCallBacks#>, <#const CFDictionaryValueCallBacks * valueCallBacks#>)
//        CFTimeInterval timeout = 1.0;
//        IOHIDDeviceSetValueMultipleWithCallback(inIOHIDDeviceRef, multiple, timeout, MyMultipltInputValueCallback, NULL)
    }
}

static void Handle_DeviceRemovalCallback(void *inContext,IOReturn inResult,void *inSender,IOHIDDeviceRef inIOHIDDeviceRef) {
    NSLog(@" pull out: %p device", (void *) inIOHIDDeviceRef);
}


int main(int argc, char * argv[]){

    int usbVendor = 0x046d;
    int usagePage = 0x01; // general usage page ...
    int usage = 0x04; // joystick

    // Create a Matching Dictionary // IOServiceMatching(kIOHIDDeviceKey);//
    CFMutableDictionaryRef matchingDict = CFDictionaryCreateMutable(kCFAllocatorDefault, 2, &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);

//    CFDictionarySetValue(matchingDict, CFSTR(kIOHIDVendorIDKey),
//            CFNumberCreate(kCFAllocatorDefault,
//                    kCFNumberSInt32Type, &usbVendor));

    // Add key for device usage page - 0x01 for "Generic Desktop"
    CFDictionarySetValue( matchingDict, CFSTR( kIOHIDPrimaryUsagePageKey ), CFNumberCreate(kCFAllocatorDefault,
            kCFNumberSInt32Type, &usagePage) );

//    // Add key for device usage - 0x04 for "Joystick"
    CFDictionarySetValue( matchingDict, CFSTR( kIOHIDPrimaryUsageKey ), CFNumberCreate(kCFAllocatorDefault,
            kCFNumberSInt32Type, &usage) );

  // not needed in this variation
//    mach_port_t             masterPort;
//    CFRunLoopSourceRef      runLoopSource;
//    kern_return_t           kr;
//
//
//    //Create a master port for communication with the I/O Kit
//    kr = IOMasterPort(MACH_PORT_NULL, &masterPort);
//    if (kr || !masterPort)
//    {
//        printf("ERR: Couldn’t create a master I/O Kit port(%08x)\n", kr);
//        return -1;
//    }
//
//    //To set up asynchronous notifications, create a notification port and
//    //add its run loop event source to the program’s run loop
//    gNotifyPort = IONotificationPortCreate(masterPort);
//    runLoopSource = IONotificationPortGetRunLoopSource(gNotifyPort);
//    CFRunLoopAddSource(CFRunLoopGetCurrent(), runLoopSource,
//            kCFRunLoopDefaultMode);


    hidManagerRef = IOHIDManagerCreate(kCFAllocatorDefault, kIOHIDOptionsTypeNone);

    IOHIDManagerRegisterDeviceMatchingCallback(hidManagerRef, Handle_DeviceMatchingCallback, NULL);
    IOHIDManagerRegisterDeviceRemovalCallback(hidManagerRef, Handle_DeviceRemovalCallback, NULL);

    // Register the Matching Dictionary to the HID Manager
    IOHIDManagerSetDeviceMatching(hidManagerRef, matchingDict);

    IOHIDManagerScheduleWithRunLoop(hidManagerRef, CFRunLoopGetMain(), kCFRunLoopDefaultMode);

  // not needed
//    IOReturn ret = IOHIDManagerOpen(hidManagerRef, kIOHIDOptionsTypeNone);
//    if (ret == kIOReturnSuccess) {
//        NSLog(@"IOHIDManager opened successfully");
//    }

    CFRunLoopRun();

    IOHIDManagerClose(hidManagerRef, 0);

    return 0;
}

Thanks! Note that the buffer supplied to IOHIDDeviceRegisterInputReportCallback() needs to be per-device and particularly not on the stack as shown.
I.e. replace

        uint8_t buf[64];

        // raw report
        IOHIDDeviceRegisterInputReportCallback(inIOHIDDeviceRef, buf, sizeof(buf), MyInputCallback, NULL);

with

        uint8_t *buf = calloc(64, sizeof(uint8_t); // alloc buffer memory

        // raw report
        IOHIDDeviceRegisterInputReportCallback(inIOHIDDeviceRef, buf, sizeof(buf), MyInputCallback, (void *)buf); // pass buf as user context

and in Handle_DeviceRemovalCallback() drop the memory by adding

        free(inContext); // free user context, i.e. the report buffer