Read the angle of the lid sensors on MacBooks (2019 and newer)

lidAngle.c

#include <IOKit/hid/IOHIDManager.h>
#include <CoreFoundation/CoreFoundation.h>
#include <stdio.h>
#include <stdlib.h>

// clang -o lidangle LidAngle.c -framework IOKit -framework CoreFoundation

static IOHIDDeviceRef findSensor(void) {
    IOHIDManagerRef manager = IOHIDManagerCreate(kCFAllocatorDefault, kIOHIDOptionsTypeNone);
    if (!manager) {
        fprintf(stderr, "Failed to create IOHIDManager\n");
        return NULL;
    }

    if (IOHIDManagerOpen(manager, kIOHIDOptionsTypeNone) != kIOReturnSuccess) {
        fprintf(stderr, "Failed to open IOHIDManager\n");
        CFRelease(manager);
        return NULL;
    }

    CFMutableDictionaryRef matching = CFDictionaryCreateMutable(kCFAllocatorDefault, 4,
                                                                &kCFTypeDictionaryKeyCallBacks,
                                                                &kCFTypeDictionaryValueCallBacks);
    
    int vendor      = 0x05AC;   CFDictionarySetValue(matching, CFSTR("VendorID"),  CFNumberCreate(NULL, kCFNumberIntType, &vendor));
    int product     = 0x8104;   CFDictionarySetValue(matching, CFSTR("ProductID"), CFNumberCreate(NULL, kCFNumberIntType, &product));
    int usagePage   = 0x0020;   CFDictionarySetValue(matching, CFSTR("UsagePage"), CFNumberCreate(NULL, kCFNumberIntType, &usagePage));
    int usage       = 0x008A;   CFDictionarySetValue(matching, CFSTR("Usage"),     CFNumberCreate(NULL, kCFNumberIntType, &usage));

    IOHIDManagerSetDeviceMatching(manager, matching);
    CFRelease(matching);

    CFSetRef devices = IOHIDManagerCopyDevices(manager);
    IOHIDDeviceRef device = NULL;

    if (devices && CFSetGetCount(devices) > 0) {
        CFIndex count = CFSetGetCount(devices);
        const void **array = malloc(sizeof(void *) * count);
        CFSetGetValues(devices, array);

        for (CFIndex i = 0; i < count; i++) {
            IOHIDDeviceRef testDevice = (IOHIDDeviceRef)array[i];
            if (IOHIDDeviceOpen(testDevice, kIOHIDOptionsTypeNone) == kIOReturnSuccess) {
                uint8_t report[8] = {0};
                CFIndex len = sizeof(report);
                IOReturn res = IOHIDDeviceGetReport(testDevice, kIOHIDReportTypeFeature, 1, report, &len);
                if (res == kIOReturnSuccess && len >= 3) { // Found working lid angle sensor
                    device = (IOHIDDeviceRef)CFRetain(testDevice);
                    IOHIDDeviceClose(testDevice, kIOHIDOptionsTypeNone);
                    break;
                }
                IOHIDDeviceClose(testDevice, kIOHIDOptionsTypeNone);
            }
        }
        free(array);
    }

    if (devices) CFRelease(devices);
    IOHIDManagerClose(manager, kIOHIDOptionsTypeNone);
    CFRelease(manager);

    return device;
}

int getLidAngle(IOHIDDeviceRef dev) {
    if (!dev) return -1;
    
    uint8_t report[8] = {0};
    CFIndex len = sizeof(report);
    IOReturn res = IOHIDDeviceGetReport(dev, kIOHIDReportTypeFeature, 1, report, &len);
    
    if (res == kIOReturnSuccess && len >= 3) {
        return (report[2] << 8) | report[1];
    }
    return -1;
}

int main(void) {
    IOHIDDeviceRef dev = findSensor();
    if (dev) {
        IOHIDDeviceOpen(dev, kIOHIDOptionsTypeNone);
        
        int angle = getLidAngle(dev);
        if (angle == 1) printf("Docked");
        else printf("Lid Angle: %d°\n", angle);
        
        IOHIDDeviceClose(dev, kIOHIDOptionsTypeNone);
        CFRelease(dev);
    } else {
        printf("No lid angle sensor found\n");
    }
    return 0;
}