On 2022-02-17 15:28, Pekka Paalanen wrote:

On Thu, 17 Feb 2022 11:42:29 +0100
Geert Uytterhoeven [off-list ref] wrote:

quoted

Hi Pekka,

On Thu, Feb 17, 2022 at 11:10 AM Pekka Paalanen [off-list ref] wrote:

quoted

On Tue, 15 Feb 2022 17:52:26 +0100
Geert Uytterhoeven [off-list ref] wrote:  

quoted

Introduce a fourcc code for a single-channel frame buffer format with two
darkness levels.  This can be used for two-level dark-on-light displays.

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

Signed-off-by: Geert Uytterhoeven <geert@linux-m68k.org>  

quoted

quoted

--- a/drivers/gpu/drm/drm_fourcc.c
+++ b/drivers/gpu/drm/drm_fourcc.c

@@ -151,6 +151,8 @@ 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 },
              { .format = DRM_FORMAT_C8,              .depth = 8,  .num_planes = 1, .cpp = { 1, 0, 0 }, .hsub = 1, .vsub = 1 },
+             { .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_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 8605a1acc6813e6c..c15c6efcc65e5827 100644
--- a/include/uapi/drm/drm_fourcc.h
+++ b/include/uapi/drm/drm_fourcc.h

@@ -104,6 +104,9 @@ extern "C" {
 #define DRM_FORMAT_C4                fourcc_code('C', '4', ' ', ' ') /* [3:0] C */
 #define DRM_FORMAT_C8                fourcc_code('C', '8', ' ', ' ') /* [7:0] C */

+/* 1 bpp Darkness */
+#define DRM_FORMAT_D1                fourcc_code('D', '1', ' ', ' ') /* [0] D */
+  

the same comment here as for C1 and R1 formats, need to specify pixel
ordering inside a byte.  

Right, will do.

Btw. does endianess of anything have any effect on these pixel formats?

That's probably a weird question, but I recall Pixman (the pixel
handling library of the X server nowadays known as Xorg) having pixel
formats where CPU endianess affects whether the first pixel in a byte
is found at the MSB or LSB.

Pixman probably has that for hysterical raisins inherited from the X code base. Conceptually, endianness is purely about the order of bytes in words, and is orthogonal to the order in which the bits of a byte/word are numbered.


-- 
Earthling Michel Dänzer            |                  https://redhat.com
Libre software enthusiast          |         Mesa and Xwayland developer