drm: Introduce new DRM_FORMAT_XYUV

v5: This is YUV444 packed format same as AYUV, but without alpha,
    as supported by i915.

v6: Removed unneeded initializer for new XYUV format.

v7: Added is_yuv field initialization according to latest
    drm_fourcc format structure initialization changes.

v8: Edited commit message to be more clear about skl+, renamed
    PLANE_CTL_FORMAT_AYUV to PLANE_CTL_FORMAT_XYUV as this format
    doesn't support per-pixel alpha. Fixed minor code issues.

v9: Moved DRM format check to proper place in intel_framebuffer_init.

v10: Changed DRM_FORMAT_XYUV to be DRM_FORMAT_XYUV8888

v11: Fixed rebase conflict, caused by added new formats to drm-tip
     meanwhile.
Reviewed-by: Alexandru Gheorghe <alexandru-cosmin.gheorghe@arm.com>
Signed-off-by: Stanislav Lisovskiy <stanislav.lisovskiy@intel.com>
[vsyrjala: Removed stray tab and sorted the formats differently]
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20181109093916.25858-2-stanislav.lisovskiy@intel.com

drivers/gpu/drm/drm_fourcc.c

@@ -224,6 +224,7 @@ const struct drm_format_info *__drm_format_info(u32 format)
 		{ .format = DRM_FORMAT_YVYU,		.depth = 0,  .num_planes = 1, .cpp = { 2, 0, 0 }, .hsub = 2, .vsub = 1, .is_yuv = true },
 		{ .format = DRM_FORMAT_UYVY,		.depth = 0,  .num_planes = 1, .cpp = { 2, 0, 0 }, .hsub = 2, .vsub = 1, .is_yuv = true },
 		{ .format = DRM_FORMAT_VYUY,		.depth = 0,  .num_planes = 1, .cpp = { 2, 0, 0 }, .hsub = 2, .vsub = 1, .is_yuv = true },
+		{ .format = DRM_FORMAT_XYUV8888,	.depth = 0,  .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1, .is_yuv = true },
 		{ .format = DRM_FORMAT_AYUV,		.depth = 0,  .num_planes = 1, .cpp = { 4, 0, 0 }, .hsub = 1, .vsub = 1, .has_alpha = true, .is_yuv = true },
 		{ .format = DRM_FORMAT_Y0L0,		.depth = 0,  .num_planes = 1,
 		  .char_per_block = { 8, 0, 0 }, .block_w = { 2, 0, 0 }, .block_h = { 2, 0, 0 },

include/uapi/drm/drm_fourcc.h

@@ -151,6 +151,7 @@ extern "C" {
 #define DRM_FORMAT_VYUY		fourcc_code('V', 'Y', 'U', 'Y') /* [31:0] Y1:Cb0:Y0:Cr0 8:8:8:8 little endian */
 
 #define DRM_FORMAT_AYUV		fourcc_code('A', 'Y', 'U', 'V') /* [31:0] A:Y:Cb:Cr 8:8:8:8 little endian */
+#define DRM_FORMAT_XYUV8888		fourcc_code('X', 'Y', 'U', 'V') /* [31:0] X:Y:Cb:Cr 8:8:8:8 little endian */
 
 /*
  * packed YCbCr420 2x2 tiled formats