From: Maxime Ripard <maxime.ripard@free-electrons.com>
Date: Mon, 22 Jan 2018 10:25:17 +0100
Subject: drm/sun4i: backend: Allow a NULL plane pointer to retrieve the format
Git-commit: 9f4ebf670d0ac92545548a6a8c74c3a980d52cfb
Patch-mainline: v4.17-rc1
References: FATE#326289 FATE#326079 FATE#326049 FATE#322398 FATE#326166

The function converting the DRM format to its equivalent in the backend
registers was assuming that we were having a plane.

However, we might want to use that function when setting up a plane using
the frontend, in which case we will not have a plane associated to the
backend's layer. Yet, we still need to setup the format to the one output
by the frontend.

Test for NULL plane pointers before referencing them, so that we can work
around it.

Reviewed-by: Neil Armstrong <narmstrong@baylibre.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Link: https://patchwork.freedesktop.org/patch/msgid/bfbe4c2e8525a7542526b648d59a8f3546e905f1.1516613040.git-series.maxime.ripard@free-electrons.com

Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/gpu/drm/sun4i/sun4i_backend.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/drivers/gpu/drm/sun4i/sun4i_backend.c
+++ b/drivers/gpu/drm/sun4i/sun4i_backend.c
@@ -93,7 +93,7 @@ void sun4i_backend_layer_enable(struct s
 static int sun4i_backend_drm_format_to_layer(struct drm_plane *plane,
 					     u32 format, u32 *mode)
 {
-	if ((plane->type == DRM_PLANE_TYPE_PRIMARY) &&
+	if (plane && (plane->type == DRM_PLANE_TYPE_PRIMARY) &&
 	    (format == DRM_FORMAT_ARGB8888))
 		format = DRM_FORMAT_XRGB8888;