types/wlr_switch: constify impl

include/wlr/interfaces/wlr_switch.h

@@ -16,7 +16,7 @@ struct wlr_switch_impl {
 };
 
 void wlr_switch_init(struct wlr_switch *switch_device,
-	struct wlr_switch_impl *impl, const char *name);
+	const struct wlr_switch_impl *impl, const char *name);
 void wlr_switch_destroy(struct wlr_switch *switch_device);
 
 #endif

include/wlr/types/wlr_switch.h

@@ -18,7 +18,7 @@ struct wlr_switch_impl;
 struct wlr_switch {
 	struct wlr_input_device base;
 
-	struct wlr_switch_impl *impl;
+	const struct wlr_switch_impl *impl;
 
 	struct {
 		struct wl_signal toggle;

types/wlr_switch.c

@@ -6,7 +6,7 @@
 #include <wlr/types/wlr_switch.h>
 
 void wlr_switch_init(struct wlr_switch *switch_device,
-		struct wlr_switch_impl *impl, const char *name) {
+		const struct wlr_switch_impl *impl, const char *name) {
 	wlr_input_device_init(&switch_device->base, WLR_INPUT_DEVICE_SWITCH, NULL,
 		name);
 	switch_device->base.switch_device = switch_device;