render/egl: add support for EGL_EXT_device_drm_render_node

This EGL extension has been added in [1]. The upsides are:

- We directly get a render node, instead of having to convert the
  primary node name to a render node name.
- If EGL_DRM_RENDER_NODE_FILE_EXT returns NULL, that means there is
  no render node being used by the driver.

[1]: https://github.com/KhronosGroup/EGL-Registry/pull/127

include/wlr/render/egl.h

@@ -43,6 +43,7 @@ struct wlr_egl {
 
 		// Device extensions
 		bool EXT_device_drm;
+		bool EXT_device_drm_render_node;
 	} exts;
 
 	struct {

render/egl.c

@@ -289,6 +289,8 @@ struct wlr_egl *wlr_egl_create_with_drm_fd(int drm_fd) {
 
 		egl->exts.EXT_device_drm =
 			check_egl_ext(device_exts_str, "EGL_EXT_device_drm");
+		egl->exts.EXT_device_drm_render_node =
+			check_egl_ext(device_exts_str, "EGL_EXT_device_drm_render_node");
 	}
 
 	if (!check_egl_ext(display_exts_str, "EGL_KHR_no_config_context") &&
@@ -712,10 +714,25 @@ static char *get_render_name(const char *name) {
 }
 
 int wlr_egl_dup_drm_fd(struct wlr_egl *egl) {
-	if (egl->device == EGL_NO_DEVICE_EXT || !egl->exts.EXT_device_drm) {
+	if (egl->device == EGL_NO_DEVICE_EXT || (!egl->exts.EXT_device_drm &&
+			!egl->exts.EXT_device_drm_render_node)) {
 		return -1;
 	}
 
+	char *render_name = NULL;
+#ifdef EGL_EXT_device_drm_render_node
+	if (egl->exts.device_drm_render_node_ext) {
+		const char *name = egl->procs.eglQueryDeviceStringEXT(egl->device,
+			EGL_DRM_RENDER_NODE_FILE_EXT);
+		if (name == NULL) {
+			wlr_log(WLR_DEBUG, "EGL device has no render node");
+			return -1;
+		}
+		render_name = strdup(name);
+	}
+#endif
+
+	if (render_name == NULL) {
 		const char *primary_name = egl->procs.eglQueryDeviceStringEXT(egl->device,
 			EGL_DRM_DEVICE_FILE_EXT);
 		if (primary_name == NULL) {
@@ -724,12 +741,13 @@ int wlr_egl_dup_drm_fd(struct wlr_egl *egl) {
 			return -1;
 		}
 
-	char *render_name = get_render_name(primary_name);
+		render_name = get_render_name(primary_name);
 		if (render_name == NULL) {
 			wlr_log(WLR_ERROR, "Can't find render node name for device %s",
 				primary_name);
 			return -1;
 		}
+	}
 
 	int render_fd = open(render_name, O_RDWR | O_NONBLOCK | O_CLOEXEC);
 	if (render_fd < 0) {