Print version number of device 1 on each raw dev.

Only works on HID++ >=2.0 so far. Also solves a race condition where
the wrong response can be sent to a request.

src/logid/backend/hidpp20/features/Root.cpp

@@ -0,0 +1,25 @@
+#include "Root.h"
+
+using namespace logid::backend::hidpp20;
+
+Root::Root(Device* dev) : Feature(dev, ID)
+{
+
+}
+
+feature_info Root::getFeature(uint16_t feature_id)
+{
+    feature_info info;
+    std::vector<uint8_t> params(2);
+    params[0] = feature_id & 0xff;
+    params[1] = (feature_id >> 8) & 0xff;
+
+    auto response = this->callFunction(Function::Ping, params);
+
+    info.feature_id = response[0];
+    info.hidden = response[1] & FeatureFlag::Hidden;
+    info.obsolete = response[1] & FeatureFlag::Obsolete;
+    info.internal = response[1] & FeatureFlag::Internal;
+
+    return info;
+}

src/logid/backend/hidpp20/features/Root.h

@@ -0,0 +1,37 @@
+#ifndef LOGID_BACKEND_HIDPP20_FEATURE_ROOT_H
+#define LOGID_BACKEND_HIDPP20_FEATURE_ROOT_H
+
+#include "../Feature.h"
+#include "../feature_defs.h"
+
+namespace logid {
+namespace backend {
+namespace hidpp20
+{
+    class Root : public Feature
+    {
+    public:
+        static const uint16_t ID = FeatureID::ROOT;
+        virtual uint16_t getID() { return ID; }
+
+        enum Function : uint8_t
+        {
+            GetFeature = 0,
+            Ping = 1
+        };
+
+        Root(Device* device);
+
+        feature_info getFeature (uint16_t feature_id);
+        void ping();
+    private:
+        enum FeatureFlag : uint8_t
+        {
+            Obsolete = 1<<7,
+            Hidden = 1<<6,
+            Internal = 1<<5
+        };
+    };
+}}}
+
+#endif //LOGID_BACKEND_HIDPP20_FEATURE_ROOT_H