Hi Pekka, On Thu, Feb 17, 2022 at 11:10 AM Pekka Paalanen <ppaalanen@xxxxxxxxx> wrote: > On Tue, 15 Feb 2022 17:52:26 +0100 > Geert Uytterhoeven <geert@xxxxxxxxxxxxxx> wrote: > > 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@xxxxxxxxxxxxxx> > > --- 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. > I think it would also be good to explain the rationale why C1 and R1 > are not suitable for this case and we need yet another 1-bit format in > the commit message. > > For posterity, of course. I roughly remember the discussions. C1 is color-indexed, which can be any two colors. R1 is light-on-dark. D1 is dark-on-light. > I also wonder if anyone would actually use D1. Should it be added > anyway? There is no rule that a pixel format must be used inside the > kernel AFAIK, but is there even a prospective userspace wanting this? > > Exposing R1 and inverting bits while copying to hardware might be > enough? That's an option. The repaper driver does that: drm_fb_xrgb8888_to_gray8(buf, 0, cma_obj->vaddr, fb, &clip); repaper_gray8_to_mono_reversed(buf, fb->width, fb->height); Can drm_framebuffer objects be backed by graphics memory, i.e. can they be displayed without copying? > > /* 1 bpp Red */ > > #define DRM_FORMAT_R1 fourcc_code('R', '1', ' ', ' ') /* [0] R */ Gr{oetje,eeting}s, Geert -- Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx In personal conversations with technical people, I call myself a hacker. But when I'm talking to journalists I just say "programmer" or something like that. -- Linus Torvalds