drm/sun4i: add support for Allwinner DE2 mixers

Allwinner have a new "Display Engine 2.0" in their new SoCs, which comes
with mixers to do graphic processing and feed data to TCON, like the old
backends and frontends.

Add support for the mixer on Allwinner V3s SoC; it's the simplest one.

Currently a lot of functions are still missing -- more investigations
are needed to gain enough information for them.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>

drivers/gpu/drm/sun4i/sun8i_layer.h

@@ -0,0 +1,36 @@
+/*
+ * Copyright (C) Icenowy Zheng <icenowy@aosc.io>
+ *
+ * Based on sun4i_layer.h, which is:
+ *   Copyright (C) 2015 Free Electrons
+ *   Copyright (C) 2015 NextThing Co
+ *
+ *   Maxime Ripard <maxime.ripard@free-electrons.com>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ */
+
+#ifndef _SUN8I_LAYER_H_
+#define _SUN8I_LAYER_H_
+
+struct sunxi_engine;
+
+struct sun8i_layer {
+	struct drm_plane	plane;
+	struct sun4i_drv	*drv;
+	struct sun8i_mixer	*mixer;
+	int			id;
+};
+
+static inline struct sun8i_layer *
+plane_to_sun8i_layer(struct drm_plane *plane)
+{
+	return container_of(plane, struct sun8i_layer, plane);
+}
+
+struct drm_plane **sun8i_layers_init(struct drm_device *drm,
+				     struct sunxi_engine *engine);
+#endif /* _SUN8I_LAYER_H_ */