drm: add RGB formats with separate alpha plane

Some hardware can read the alpha components separately and then
conditionally fetch color components only for non-zero alpha values.
This patch adds fourcc definitions for two-plane RGB formats with an
8-bit alpha channel on a second plane.
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>

drivers/gpu/drm/drm_fourcc.c

@@ -132,6 +132,8 @@ const struct drm_format_info *__drm_format_info(u32 format)
 		{ .format = DRM_FORMAT_XBGR8888,	.depth = 24, .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
 		{ .format = DRM_FORMAT_RGBX8888,	.depth = 24, .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
 		{ .format = DRM_FORMAT_BGRX8888,	.depth = 24, .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
+		{ .format = DRM_FORMAT_RGB565_A8,	.depth = 24, .num_planes = 2, .cpp = { 2, 1, 0 }, .hsub = 1, .vsub = 1 },
+		{ .format = DRM_FORMAT_BGR565_A8,	.depth = 24, .num_planes = 2, .cpp = { 2, 1, 0 }, .hsub = 1, .vsub = 1 },
 		{ .format = DRM_FORMAT_XRGB2101010,	.depth = 30, .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
 		{ .format = DRM_FORMAT_XBGR2101010,	.depth = 30, .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
 		{ .format = DRM_FORMAT_RGBX1010102,	.depth = 30, .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
@@ -144,6 +146,12 @@ const struct drm_format_info *__drm_format_info(u32 format)
 		{ .format = DRM_FORMAT_ABGR8888,	.depth = 32, .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
 		{ .format = DRM_FORMAT_RGBA8888,	.depth = 32, .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
 		{ .format = DRM_FORMAT_BGRA8888,	.depth = 32, .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1 },
+		{ .format = DRM_FORMAT_RGB888_A8,	.depth = 32, .num_planes = 2, .cpp = { 3, 1, 0 }, .hsub = 1, .vsub = 1 },
+		{ .format = DRM_FORMAT_BGR888_A8,	.depth = 32, .num_planes = 2, .cpp = { 3, 1, 0 }, .hsub = 1, .vsub = 1 },
+		{ .format = DRM_FORMAT_XRGB8888_A8,	.depth = 32, .num_planes = 2, .cpp = { 4, 1, 0 }, .hsub = 1, .vsub = 1 },
+		{ .format = DRM_FORMAT_XBGR8888_A8,	.depth = 32, .num_planes = 2, .cpp = { 4, 1, 0 }, .hsub = 1, .vsub = 1 },
+		{ .format = DRM_FORMAT_RGBX8888_A8,	.depth = 32, .num_planes = 2, .cpp = { 4, 1, 0 }, .hsub = 1, .vsub = 1 },
+		{ .format = DRM_FORMAT_BGRX8888_A8,	.depth = 32, .num_planes = 2, .cpp = { 4, 1, 0 }, .hsub = 1, .vsub = 1 },
 		{ .format = DRM_FORMAT_YUV410,		.depth = 0,  .num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 4, .vsub = 4 },
 		{ .format = DRM_FORMAT_YVU410,		.depth = 0,  .num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 4, .vsub = 4 },
 		{ .format = DRM_FORMAT_YUV411,		.depth = 0,  .num_planes = 3, .cpp = { 1, 1, 1 }, .hsub = 4, .vsub = 1 },

include/uapi/drm/drm_fourcc.h

@@ -113,6 +113,20 @@ extern "C" {
 
 #define DRM_FORMAT_AYUV		fourcc_code('A', 'Y', 'U', 'V') /* [31:0] A:Y:Cb:Cr 8:8:8:8 little endian */
 
+/*
+ * 2 plane RGB + A
+ * index 0 = RGB plane, same format as the corresponding non _A8 format has
+ * index 1 = A plane, [7:0] A
+ */
+#define DRM_FORMAT_XRGB8888_A8	fourcc_code('X', 'R', 'A', '8')
+#define DRM_FORMAT_XBGR8888_A8	fourcc_code('X', 'B', 'A', '8')
+#define DRM_FORMAT_RGBX8888_A8	fourcc_code('R', 'X', 'A', '8')
+#define DRM_FORMAT_BGRX8888_A8	fourcc_code('B', 'X', 'A', '8')
+#define DRM_FORMAT_RGB888_A8	fourcc_code('R', '8', 'A', '8')
+#define DRM_FORMAT_BGR888_A8	fourcc_code('B', '8', 'A', '8')
+#define DRM_FORMAT_RGB565_A8	fourcc_code('R', '5', 'A', '8')
+#define DRM_FORMAT_BGR565_A8	fourcc_code('B', '5', 'A', '8')
+
 /*
  * 2 plane YCbCr
  * index 0 = Y plane, [7:0] Y