Fixed bug 2477 - [PATCH] Joysticks do not work on RHEL6/CentOS6 systems

Ashley Whetter

RHEL6 and CentOS6 systems still use an old version of udev (147). It wasn't until udev 148 (Yep. 1 version off!) that the input class system changed from "ID_CLASS" to "ID_INPUT_{JOYSTICK,KEYBOARD,MOUSE,etc}" (http://lwn.net/Articles/364728/). Because SDL2 looks for the ID_INPUT_X field this means that it never detects any input devices on RHEL6 systems.

I've attached a patch which fixes the problem. If no input devices are detected with "ID_INPUT_X" then SDL will fallback to looking for the old style "ID_CLASS" udev field instead.
Because of the "big change" between udev versions I doubt it'll ever get upgraded on RHEL6, but because RHEL7 is on the way I don't know if this patch is worth merging. Hopefully it'll help anyone out that's having this problem though.

src/core/linux/SDL_udev.c

@@ -308,7 +308,21 @@ device_event(SDL_UDEV_deviceevent type, struct udev_device *dev)
         }
 
         if (devclass == 0) {
-            return;
+            // Fall back to old style input classes
+            val = _this->udev_device_get_property_value(dev, "ID_CLASS");
+            if (val != NULL) {
+                if (SDL_strcmp(val, "joystick") == 0) {
+                    devclass = SDL_UDEV_DEVICE_JOYSTICK;
+                } else if (SDL_strcmp(val, "mouse") == 0) {
+                    devclass = SDL_UDEV_DEVICE_MOUSE;
+                } else if (SDL_strcmp(val, "kbd") == 0) {
+                    devclass = SDL_UDEV_DEVICE_KEYBOARD;
+                } else {
+                    return;
+                }
+            } else {
+                return;
+            }
         }
     } else {
         return;