HidDevice: add GetTopLevelUsage to simply retrieve the top level collection type

Signed-off-by: Benedek Kupper <kupper.benedek@gmail.com>

Author: benedekkupper

HidSharp/HidDevice.cs

@@ -19,6 +19,7 @@ under the License. */
 using System.ComponentModel;
 using System.Globalization;
 using System.IO;
+using System.Linq;
 using System.Runtime.InteropServices;
 using HidSharp.Reports;
 
@@ -99,6 +100,13 @@ public virtual byte[] GetRawReportDescriptor()
             throw new NotSupportedException(); // Windows reconstructs it. Linux can retrieve it. MacOS 10.8+ can retrieve it as well.
         }
 
+        public uint GetTopLevelUsage()
+        {
+            var reportDescriptor = GetReportDescriptor();
+            var ditem = reportDescriptor.DeviceItems.FirstOrDefault();
+            return ditem.Usages.GetAllValues().FirstOrDefault();
+        }
+
         /*
         TODO
         public virtual string[] GetDevicePathHierarchy()