drm: WARN on illegal aspect ratio when converting a mode to umode

WARN if the incoming drm_display_mode has an illegal aspect ratio
when converting it to a user mode. This should never happen unless
the driver made a mistake and put an invalid value into the aspect
ratio.

Cc: Ilia Mirkin <imirkin@alum.mit.edu>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190620142639.17518-4-ville.syrjala@linux.intel.comReviewed-by: Alex Deucher <alexander.deucher@amd.com>

drivers/gpu/drm/drm_modes.c

@@ -1906,8 +1906,11 @@ void drm_mode_convert_to_umode(struct drm_mode_modeinfo *out,
 	case HDMI_PICTURE_ASPECT_256_135:
 		out->flags |= DRM_MODE_FLAG_PIC_AR_256_135;
 		break;
-	case HDMI_PICTURE_ASPECT_RESERVED:
 	default:
+		WARN(1, "Invalid aspect ratio (0%x) on mode\n",
+		     in->picture_aspect_ratio);
+		/* fall through */
+	case HDMI_PICTURE_ASPECT_NONE:
 		out->flags |= DRM_MODE_FLAG_PIC_AR_NONE;
 		break;
 	}