[PATCH v3 05/10] drm/fourcc: Add DRM_FORMAT_C[124]

Geert Uytterhoeven
2022-07-08T18:21:37Z

Introduce fourcc codes for color-indexed frame buffer formats with two,
four, and sixteen colors, and provide a mapping from bits per pixel and
depth to fourcc codes.

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 indexed-color (2, 4, and 16 colors) images
in the PNG specification, Version 1.2.
This order is also the recommended and default order (FillOrder = 1) for
palette-color (16 colors) images in the TIFF 6.0 Specification, and is
also used for 16-color Linux frame buffer logos.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
Reviewed-by: Pekka Paalanen <pekka.paalanen@collabora.com>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
---
v3:
- Add Reviewed-by,
- Document fill order,

v2:
- Improve pixel description,
- Require depth to match bpp in drm_mode_legacy_fb_format(),
- Set .is_color_indexed flag.
---
drivers/gpu/drm/drm_fourcc.c | 21 +++++++++++++++++++++
include/uapi/drm/drm_fourcc.h | 3 +++
2 files changed, 24 insertions(+)

diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
index 6c76bd821d17e7c7..29f4fe199c4ddcf0 100644
--- a/drivers/gpu/drm/drm_fourcc.c
+++ b/drivers/gpu/drm/drm_fourcc.c
@@ -43,6 +43,21 @@ uint32_t drm_mode_legacy_fb_format(uint32_t bpp, uint32_t depth)
uint32_t fmt = DRM_FORMAT_INVALID;

switch (bpp) {
+ case 1:
+ if (depth == 1)
+ fmt = DRM_FORMAT_C1;
+ break;
+
+ case 2:
+ if (depth == 2)
+ fmt = DRM_FORMAT_C2;
+ break;
+
+ case 4:
+ if (depth == 4)
+ fmt = DRM_FORMAT_C4;
+ break;
+
case 8:
if (depth == 8)
fmt = DRM_FORMAT_C8;
@@ -132,6 +147,12 @@ EXPORT_SYMBOL(drm_driver_legacy_fb_format);
const struct drm_format_info *__drm_format_info(u32 format)
{
static const struct drm_format_info formats[] = {
+ { .format = DRM_FORMAT_C1, .depth = 1, .num_planes = 1,
+ .char_per_block = { 1, }, .block_w = { 8, }, .block_h = { 1, }, .hsub = 1, .vsub = 1, .is_color_indexed = true },
+ { .format = DRM_FORMAT_C2, .depth = 2, .num_planes = 1,
+ .char_per_block = { 1, }, .block_w = { 4, }, .block_h = { 1, }, .hsub = 1, .vsub = 1, .is_color_indexed = true },
+ { .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_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 },
diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
index 0980678d502dc784..e18de6f258302673 100644
--- a/include/uapi/drm/drm_fourcc.h
+++ b/include/uapi/drm/drm_fourcc.h
@@ -99,6 +99,9 @@ extern "C" {
#define DRM_FORMAT_INVALID 0

/* color index */
+#define DRM_FORMAT_C1 fourcc_code('C', '1', ' ', ' ') /* [7:0] C0:C1:C2:C3:C4:C5:C6:C7 1:1:1:1:1:1:1:1 eight pixels/byte */
+#define DRM_FORMAT_C2 fourcc_code('C', '2', ' ', ' ') /* [7:0] C0:C1:C2:C3 2:2:2:2 four pixels/byte */
+#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 bpp Red */
--
2.25.1