[PATCH v2 RFC 10/10] drm/fourcc: Add DRM_FORMAT_D[1248]

[Geert Uytterhoeven]

As Rn is light-on-dark, and Cn can be any colors, there are currently
no fourcc codes to describe dark-on-light displays.

Introduce fourcc codes for a single-channel dark-on-light frame buffer
format with two, four, sixteen, or 256 darkness levels.

As the number of bits per pixel may be less than eight, some of these
formats rely on proper block handling for the calculation of bits per
pixel and pitch.

Signed-off-by: Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>
---
RFC, as I have no immediate need for these formats.

v2:
  - Add rationale for adding new formats,
  - Improve pixel descriptions,
  - Add D[248] for completeness.
---
 drivers/gpu/drm/drm_fourcc.c  |  7 +++++++
 include/uapi/drm/drm_fourcc.h | 12 ++++++++++++
 2 files changed, 19 insertions(+)

diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
index 05e65e9ab0c69c6a..e09331bb3bc73f21 100644
--- a/drivers/gpu/drm/drm_fourcc.c
+++ b/drivers/gpu/drm/drm_fourcc.c
@@ -154,6 +154,13 @@ const struct drm_format_info *__drm_format_info(u32 format)
 		{ .format = DRM_FORMAT_C4,		.depth = 4,  .num_planes = 1,
 		  .char_per_block = { 1, }, .block_w = { 2, }, .block_h = { 1, }, .hsub = 1, .vsub = 1, .is_color_indexed = true },
 		{ .format = DRM_FORMAT_C8,		.depth = 8,  .num_planes = 1, .cpp = { 1, 0, 0 }, .hsub = 1, .vsub = 1, .is_color_indexed = true },
+		{ .format = DRM_FORMAT_D1,		.depth = 1,  .num_planes = 1,
+		  .char_per_block = { 1, }, .block_w = { 8, }, .block_h = { 1, }, .hsub = 1, .vsub = 1 },
+		{ .format = DRM_FORMAT_D2,		.depth = 2,  .num_planes = 1,
+		  .char_per_block = { 1, }, .block_w = { 4, }, .block_h = { 1, }, .hsub = 1, .vsub = 1 },
+		{ .format = DRM_FORMAT_D4,		.depth = 4,  .num_planes = 1,
+		  .char_per_block = { 1, }, .block_w = { 2, }, .block_h = { 1, }, .hsub = 1, .vsub = 1 },
+		{ .format = DRM_FORMAT_D8,		.depth = 8,  .num_planes = 1, .cpp = { 1, 0, 0 }, .hsub = 1, .vsub = 1 },
 		{ .format = DRM_FORMAT_R1,		.depth = 1,  .num_planes = 1,
 		  .char_per_block = { 1, }, .block_w = { 8, }, .block_h = { 1, }, .hsub = 1, .vsub = 1 },
 		{ .format = DRM_FORMAT_R2,		.depth = 2,  .num_planes = 1,
diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
index def0a73620dc86d2..1d8d82b1742898c0 100644
--- a/include/uapi/drm/drm_fourcc.h
+++ b/include/uapi/drm/drm_fourcc.h
@@ -104,6 +104,18 @@ extern "C" {
 #define DRM_FORMAT_C4		fourcc_code('C', '4', ' ', ' ') /* [7:0] C0:C1 4:4 two pixels/byte */
 #define DRM_FORMAT_C8		fourcc_code('C', '8', ' ', ' ') /* [7:0] C 8 one pixel/byte */
 
+/* 1 bpp Darkness (monochrome dark-on-light) */
+#define DRM_FORMAT_D1		fourcc_code('D', '1', ' ', ' ') /* [7:0] D0:D1:D2:D3:D4:D5:D6:D7 1:1:1:1:1:1:1:1 eight pixels/byte */
+
+/* 2 bpp Darkness (generic dark-on-light) */
+#define DRM_FORMAT_D2		fourcc_code('D', '2', ' ', ' ') /* [7:0] D0:D1:D2:D3 2:2:2:2 four pixels/byte */
+
+/* 4 bpp Darkness (generic dark-on-light) */
+#define DRM_FORMAT_D4		fourcc_code('D', '4', ' ', ' ') /* [7:0] D0:D1 4:4 two pixels/byte */
+
+/* 8 bpp Darkness (generic dark-on-light) */
+#define DRM_FORMAT_D8		fourcc_code('D', '8', ' ', ' ') /* [7:0] D 8 one pixel/byte */
+
 /* 1 bpp Red (or monochrome light-on-dark) */
 #define DRM_FORMAT_R1		fourcc_code('R', '1', ' ', ' ') /* [7:0] R0:R1:R2:R3:R4:R5:R6:R7 1:1:1:1:1:1:1:1 eight pixels/byte */
 
-- 
2.25.1