KEY_MAX is 511, which does not fit in a BYTE.

dlls/dinput/joystick/linuxinput.c

diff --git a/dlls/dinput/joystick/linuxinput.c b/dlls/dinput/joystick/linuxinput.c
index 050dcc4..bed576e 100644
--- a/dlls/dinput/joystick/linuxinput.c
+++ b/dlls/dinput/joystick/linuxinput.c
@@ -775,7 +775,7 @@
 
   if ((dwFlags == DIDFT_ALL) ||
       (dwFlags & DIDFT_BUTTON)) {
-    BYTE i;
+    int i;
 
     /*The DInput SDK says that GUID_Button is only for mouse buttons but well*/