TryOpenKbd.cs

// Can userspace read the RAW keyboard report - the one containing Apple's fn bit
// (vendor usage 0xFF00:0x03)? Tries every access combination that might work.
using System;
using System.Runtime.InteropServices;

class TryOpenKbd {
    const uint GENERIC_READ = 0x80000000, GENERIC_WRITE = 0x40000000;
    const uint SHARE_R = 1, SHARE_W = 2, OPEN_EXISTING = 3;
    static readonly IntPtr INVALID = new IntPtr(-1);

    [DllImport("kernel32.dll", CharSet = CharSet.Unicode, SetLastError = true)]
    static extern IntPtr CreateFile(string p, uint a, uint s, IntPtr sa, uint d, uint f, IntPtr t);
    [DllImport("kernel32.dll", SetLastError = true)]
    static extern bool ReadFile(IntPtr h, byte[] b, int n, out int r, IntPtr o);
    [DllImport("kernel32.dll")] static extern bool CloseHandle(IntPtr h);

    static void Try(string label, string path, uint access, uint share) {
        IntPtr h = CreateFile(path, access, share, IntPtr.Zero, OPEN_EXISTING, 0, IntPtr.Zero);
        if (h == INVALID) {
            int e = Marshal.GetLastWin32Error();
            Console.WriteLine(string.Format("  {0,-34} FAILED  err={1} {2}", label, e,
                e == 5 ? "(ACCESS_DENIED - held exclusively by the OS)" : ""));
            return;
        }
        Console.WriteLine(string.Format("  {0,-34} OPENED", label));
        if ((access & GENERIC_READ) != 0) {
            var buf = new byte[10];
            int got;
            bool ok = ReadFile(h, buf, buf.Length, out got, IntPtr.Zero);
            Console.WriteLine(string.Format("      ReadFile -> {0} err={1}", ok, ok ? 0 : Marshal.GetLastWin32Error()));
        }
        CloseHandle(h);
    }

    static void Main(string[] argv) {
        string kbd = @"\\?\hid#{00001124-0000-1000-8000-00805f9b34fb}_vid&0001004c_pid&029c&col01#b&2d27471b&5&0000#{4d1e55b2-f16f-11cf-88cb-001111000030}";
        Console.WriteLine("Attempting raw access to the Magic Keyboard's keyboard collection (COL01):");
        Try("GENERIC_READ, share R|W",   kbd, GENERIC_READ, SHARE_R | SHARE_W);
        Try("GENERIC_READ, share R",     kbd, GENERIC_READ, SHARE_R);
        Try("GENERIC_READ, no sharing",  kbd, GENERIC_READ, 0);
        Try("GENERIC_R|W, share R|W",    kbd, GENERIC_READ | GENERIC_WRITE, SHARE_R | SHARE_W);
        Try("no access (query only)",    kbd, 0, SHARE_R | SHARE_W);
        Console.WriteLine();
        Console.WriteLine("Also trying the \\kbd suffixed interface Windows itself uses:");
        Try("GENERIC_READ on \\kbd", kbd + @"\kbd", GENERIC_READ, SHARE_R | SHARE_W);
    }
}