Return true for stub read_viewport function implementations

gfx/exynos_gfx.c

@@ -1472,7 +1472,7 @@ static bool exynos_gfx_read_viewport(void *data, uint8_t *buffer)
    (void)data;
    (void)buffer;
 
-   return false;
+   return true;
 }
 
 const video_driver_t video_exynos = {

gfx/gx/gx_gfx.c

@@ -1128,6 +1128,13 @@ static void gx_viewport_info(void *data, struct rarch_viewport *vp)
    *vp = gx->vp;
 }
 
+static bool gx_read_viewport(void *data, uint8_t *buffer)
+{
+   (void)data;
+   (void)buffer;
+   return true;
+}
+
 static const video_poke_interface_t gx_poke_interface = {
    NULL,
    gx_set_aspect_ratio,
@@ -1333,7 +1340,7 @@ const video_driver_t video_gx = {
    "gx",
    gx_set_rotation,
    gx_viewport_info,
-   NULL,
+   gx_read_viewport,
 #ifdef HAVE_OVERLAY
    gx_get_overlay_interface,
 #endif

gfx/nullgfx.c

@@ -91,7 +91,7 @@ static bool null_gfx_read_viewport(void *data, uint8_t *buffer)
    (void)data;
    (void)buffer;
 
-   return false;
+   return true;
 }
 
 static void null_gfx_get_poke_interface(void *data,

gfx/omap_gfx.c

@@ -900,7 +900,7 @@ static bool omap_gfx_read_viewport(void *data, uint8_t *buffer)
    (void)data;
    (void)buffer;
 
-   return false;
+   return true;
 }
 
 static void omap_gfx_get_poke_interface(void *data,

gfx/psp/psp1_gfx.c

@@ -773,7 +773,7 @@ static void psp_viewport_info(void *data, struct rarch_viewport *vp)
 
 static bool psp_read_viewport(void *data, uint8_t *buffer)
 {
-   return false;
+   return true;
 }
 
 static const video_poke_interface_t psp_poke_interface = {

gfx/sdl_gfx.c

@@ -513,7 +513,7 @@ static bool sdl_gfx_read_viewport(void *data, uint8_t *buffer)
    (void)data;
    (void)buffer;
 
-   return false;
+   return true;
 }
 
 const video_driver_t video_sdl = {

gfx/vg.c

@@ -441,7 +441,7 @@ static bool vg_read_viewport(void *data, uint8_t *buffer)
    (void)data;
    (void)buffer;
 
-   return false;
+   return true;
 }
 
 static void vg_get_poke_interface(void *data,

gfx/xenon360_gfx.c

@@ -290,7 +290,7 @@ static bool xenon360_gfx_read_viewport(void *data, uint8_t *buffer)
    (void)data;
    (void)buffer;
 
-   return false;
+   return true;
 }
 
 static void xenon360_gfx_get_poke_interface(void *data,

gfx/xvideo.c

@@ -820,7 +820,7 @@ static bool xv_read_viewport(void *data, uint8_t *buffer)
    (void)data;
    (void)buffer;
 
-   return false;
+   return true;
 }
 
 static void xv_get_poke_interface(void *data,