Restrict DSU joystick support to specific platforms

Updated CMakeLists.txt to enable DSU joystick support only on Windows, Linux, Android, Haiku, FreeBSD, NetBSD, OpenBSD, and macOS. Added conditional inclusion of <sys/ioctl.h> in SDL_dsujoystick.c. Removed unused GetDSUMutex helper from SDL_dsujoystick_driver.c.

Author: danprice142

CMakeLists.txt

@@ -1377,7 +1377,7 @@ if(SDL_JOYSTICK)
   endif()
 
   # DSU (DualShock UDP) client support
-  if(SDL_DSU_JOYSTICK AND NOT EMSCRIPTEN)
+  if(SDL_DSU_JOYSTICK AND NOT EMSCRIPTEN AND (WINDOWS OR LINUX OR ANDROID OR HAIKU OR FREEBSD OR NETBSD OR OPENBSD OR MACOS))
     set(SDL_JOYSTICK_DSU 1)
     sdl_glob_sources(
       "${SDL3_SOURCE_DIR}/src/joystick/dsu/*.c"

src/joystick/dsu/SDL_dsujoystick.c

@@ -61,7 +61,9 @@ typedef int socklen_t;
     #include <fcntl.h>
     #include <unistd.h>
     #include <errno.h>
-    #include <sys/ioctl.h>
+    #ifdef HAVE_SYS_IOCTL_H
+        #include <sys/ioctl.h>
+    #endif
     #ifdef __sun
         #include <sys/filio.h>
     #endif

src/joystick/dsu/SDL_dsujoystick_driver.c

@@ -64,12 +64,6 @@ extern SDL_JoystickDriver SDL_DSU_JoystickDriver;
 /* Global DSU context pointer */
 struct DSU_Context_t *s_dsu_ctx = NULL;
 
-/* Helper function to work around macro issues */
-static SDL_INLINE SDL_Mutex* GetDSUMutex(void) {
-    struct DSU_Context_t *ctx = s_dsu_ctx;
-    return ctx ? ctx->slots_mutex : NULL;
-}
-
 /* Forward declarations */
 extern int SDLCALL DSU_ReceiverThread(void *data);
 extern void DSU_RequestControllerInfo(struct DSU_Context_t *ctx, Uint8 slot);