[PATCH 1/8] drm/fourcc: Add DRM_FORMAT_C[124]

Geert Uytterhoeven
2022-02-15T16:52:49Z

Introduce fourcc codes for color-indexed frame buffer formats with two,
four, and sixteen color, and provide a suitable mapping from bit 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.

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>
---
Do we want to keep the rounding down if depth < bpp, or insist on depth
== bpp? I don't think the rounding down will still be needed after
"[PATCH 4/8] drm/client: Use actual bpp when allocating frame buffers".
---
drivers/gpu/drm/drm_fourcc.c | 18 ++++++++++++++++++
include/uapi/drm/drm_fourcc.h | 3 +++
2 files changed, 21 insertions(+)

diff --git a/drivers/gpu/drm/drm_fourcc.c b/drivers/gpu/drm/drm_fourcc.c
index 07741b678798b0f1..60ce63d728b8e308 100644
--- a/drivers/gpu/drm/drm_fourcc.c
+++ b/drivers/gpu/drm/drm_fourcc.c
@@ -46,6 +46,18 @@ uint32_t drm_mode_legacy_fb_format(uint32_t bpp, uint32_t depth)
case 8:
if (depth == 8)
fmt = DRM_FORMAT_C8;
+ fallthrough;
+ case 4:
+ if (depth == 4)
+ fmt = DRM_FORMAT_C4;
+ fallthrough;
+ case 2:
+ if (depth == 2)
+ fmt = DRM_FORMAT_C2;
+ fallthrough;
+ case 1:
+ if (depth == 1)
+ fmt = DRM_FORMAT_C1;
break;

case 16:
@@ -132,6 +144,12 @@ 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 },
+ { .format = DRM_FORMAT_C2, .depth = 2, .num_planes = 1,
+ .char_per_block = { 1, }, .block_w = { 4, }, .block_h = { 1, }, .hsub = 1, .vsub = 1 },
+ { .format = DRM_FORMAT_C4, .depth = 4, .num_planes = 1,
+ .char_per_block = { 1, }, .block_w = { 2, }, .block_h = { 1, }, .hsub = 1, .vsub = 1 },
{ .format = DRM_FORMAT_C8, .depth = 8, .num_planes = 1, .cpp = { 1, 0, 0 }, .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 },
diff --git a/include/uapi/drm/drm_fourcc.h b/include/uapi/drm/drm_fourcc.h
index fc0c1454d2757d5d..3f09174670b3cce6 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', ' ', ' ') /* [0] C */
+#define DRM_FORMAT_C2 fourcc_code('C', '2', ' ', ' ') /* [1:0] C */
+#define DRM_FORMAT_C4 fourcc_code('C', '4', ' ', ' ') /* [3:0] C */
#define DRM_FORMAT_C8 fourcc_code('C', '8', ' ', ' ') /* [7:0] C */

/* 8 bpp Red */
--
2.25.1