backend-drm: move code that creates gbm surface to a separate function

The function drm_output_init_egl() is too big, so move the code to
create the gbm surface to a separate function: create_gbm_surface().

Also made some minor style changes to the code that has been moved, in
order to improve readability.

Signed-off-by: Leandro Ribeiro <leandro.ribeiro@collabora.com>

libweston/backend-drm/drm-gbm.c

@@ -177,58 +177,59 @@ err:
 	return -1;
 }
 
-/* Init output state that depends on gl or gbm */
-int
-drm_output_init_egl(struct drm_output *output, struct drm_backend *b)
+static void
+create_gbm_surface(struct gbm_device *gbm, struct drm_output *output)
 {
+	struct weston_mode *mode = output->base.current_mode;
+	struct drm_plane *plane = output->scanout_plane;
 	struct weston_drm_format *fmt;
 	const uint64_t *modifiers;
 	unsigned int num_modifiers;
 
-	uint32_t format[2] = {
-		output->gbm_format,
-		fallback_format_for(output->gbm_format),
-	};
-	struct gl_renderer_output_options options = {
-		.drm_formats = format,
-		.drm_formats_count = 1,
-	};
-	struct weston_mode *mode = output->base.current_mode;
-	struct drm_plane *plane = output->scanout_plane;
-
-	assert(output->gbm_surface == NULL);
-
-	fmt = weston_drm_format_array_find_format(&plane->formats, output->gbm_format);
+	fmt = weston_drm_format_array_find_format(&plane->formats,
+						  output->gbm_format);
 	if (!fmt) {
 		weston_log("format 0x%x not supported by output %s\n",
 			   output->gbm_format, output->base.name);
-		return -1;
+		return;
 	}
 
 #ifdef HAVE_GBM_MODIFIERS
 	modifiers = weston_drm_format_get_modifiers(fmt, &num_modifiers);
 	if (num_modifiers > 0) {
 		output->gbm_surface =
-			gbm_surface_create_with_modifiers(b->gbm,
-							  mode->width,
-							  mode->height,
+			gbm_surface_create_with_modifiers(gbm,
+							  mode->width, mode->height,
 							  output->gbm_format,
-							  modifiers,
-							  num_modifiers);
+							  modifiers, num_modifiers);
 	}
+#endif
 
 	/* If allocating with modifiers fails, try again without. This can
 	 * happen when the KMS display device supports modifiers but the
 	 * GBM driver does not, e.g. the old i915 Mesa driver. */
 	if (!output->gbm_surface)
-#endif
-	{
-		output->gbm_surface =
-		    gbm_surface_create(b->gbm, mode->width, mode->height,
-				       output->gbm_format,
-				       output->gbm_bo_flags);
-	}
+		output->gbm_surface = gbm_surface_create(gbm,
+							 mode->width, mode->height,
+							 output->gbm_format,
+							 output->gbm_bo_flags);
+}
+
+/* Init output state that depends on gl or gbm */
+int
+drm_output_init_egl(struct drm_output *output, struct drm_backend *b)
+{
+	uint32_t format[2] = {
+		output->gbm_format,
+		fallback_format_for(output->gbm_format),
+	};
+	struct gl_renderer_output_options options = {
+		.drm_formats = format,
+		.drm_formats_count = 1,
+	};
 
+	assert(output->gbm_surface == NULL);
+	create_gbm_surface(b->gbm, output);
 	if (!output->gbm_surface) {
 		weston_log("failed to create gbm surface\n");
 		return -1;