backend_kms.c

	switch (format) {
		// 32bpp
	case GBM_FORMAT_ARGB8888:
	case GBM_FORMAT_XRGB8888:
		break;
	default:
		// unsupported...
		goto error;
	}

gbm_dri.c

   switch (format) {
/* --- 8< --- 8< --- removed some code --- 8< --- 8< --- */
   case GBM_FORMAT_XRGB8888:
   case GBM_BO_FORMAT_XRGB8888:
      dri_format = __DRI_IMAGE_FORMAT_XRGB8888;
      break;
/* --- 8< --- 8< --- removed some code --- 8< --- 8< --- */
   case GBM_FORMAT_ARGB8888:
   case GBM_BO_FORMAT_ARGB8888:
      dri_format = __DRI_IMAGE_FORMAT_ARGB8888;
      break;
/* --- 8< --- 8< --- removed some code --- 8< --- 8< --- */
   default:
      errno = EINVAL;
      goto failed;
   }