Define constants not available on older kernels
diff --git a/src/joystick/linux/SDL_sysjoystick.c b/src/joystick/linux/SDL_sysjoystick.c
index f5d9452..45b7960 100644
--- a/src/joystick/linux/SDL_sysjoystick.c
+++ b/src/joystick/linux/SDL_sysjoystick.c
@@ -52,6 +52,30 @@
#ifndef SYN_DROPPED
#define SYN_DROPPED 3
#endif
+#ifndef BTN_SOUTH
+#define BTN_SOUTH 0x130
+#endif
+#ifndef BTN_EAST
+#define BTN_EAST 0x131
+#endif
+#ifndef BTN_NORTH
+#define BTN_NORTH 0x133
+#endif
+#ifndef BTN_WEST
+#define BTN_WEST 0x134
+#endif
+#ifndef BTN_DPAD_UP
+#define BTN_DPAD_UP 0x220
+#endif
+#ifndef BTN_DPAD_DOWN
+#define BTN_DPAD_DOWN 0x221
+#endif
+#ifndef BTN_DPAD_LEFT
+#define BTN_DPAD_LEFT 0x222
+#endif
+#ifndef BTN_DPAD_RIGHT
+#define BTN_DPAD_RIGHT 0x223
+#endif
#include "../../core/linux/SDL_udev.h"