drm/fourcc: Add DRM_FORMAT_R[124]

Introduce fourcc codes for single-channel frame buffer formats with two,
four, and sixteen brightness levels, where there is a direct
relationship between channel value and brightness.

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

The fill order (the order in which multiple pixels are packed in a byte)
is the same order as used for grayscale (2, 4, and 16 levels) images in
the PNG specification, Version 1.2.
This order is also the recommended and default order (FillOrder = 1) for
bilevel and grayscale (16 levels) images in the TIFF 6.0 Specification,
and is also used for monochrome images in the PBM file format,
monochrome Linux frame buffer logos, and BDF and PSF (Linux kernel) font
files.
Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Link: https://patchwork.freedesktop.org/patch/msgid/96561a88e53c59cac72e66642bf4c097aacefd18.1657294931.git.geert@linux-m68k.org

drivers/gpu/drm/drm_fourcc.c

@@ -154,6 +154,12 @@ 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_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,
+		  .char_per_block = { 1, }, .block_w = { 4, }, .block_h = { 1, }, .hsub = 1, .vsub = 1 },
+		{ .format = DRM_FORMAT_R4,		.depth = 4,  .num_planes = 1,
+		  .char_per_block = { 1, }, .block_w = { 2, }, .block_h = { 1, }, .hsub = 1, .vsub = 1 },
 		{ .format = DRM_FORMAT_R8,		.depth = 8,  .num_planes = 1, .cpp = { 1, 0, 0 }, .hsub = 1, .vsub = 1 },
 		{ .format = DRM_FORMAT_R10,		.depth = 10, .num_planes = 1, .cpp = { 2, 0, 0 }, .hsub = 1, .vsub = 1 },
 		{ .format = DRM_FORMAT_R12,		.depth = 12, .num_planes = 1, .cpp = { 2, 0, 0 }, .hsub = 1, .vsub = 1 },

include/uapi/drm/drm_fourcc.h

@@ -104,6 +104,15 @@ 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 */
 
+/* 1 bpp Red (direct relationship between channel value and brightness) */
+#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 bpp Red (direct relationship between channel value and brightness) */
+#define DRM_FORMAT_R2		fourcc_code('R', '2', ' ', ' ') /* [7:0] R0:R1:R2:R3 2:2:2:2 four pixels/byte */
+
+/* 4 bpp Red (direct relationship between channel value and brightness) */
+#define DRM_FORMAT_R4		fourcc_code('R', '4', ' ', ' ') /* [7:0] R0:R1 4:4 two pixels/byte */
+
 /* 8 bpp Red (direct relationship between channel value and brightness) */
 #define DRM_FORMAT_R8		fourcc_code('R', '8', ' ', ' ') /* [7:0] R */