From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Pekka Paalanen <ppaalanen@gmail.com>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
Maxime Ripard <mripard@kernel.org>,
Thomas Zimmermann <tzimmermann@suse.de>,
David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>,
Helge Deller <deller@gmx.de>,
Javier Martinez Canillas <javierm@redhat.com>,
Linux Fbdev development list <linux-fbdev@vger.kernel.org>,
"Linux/m68k" <linux-m68k@vger.kernel.org>,
DRI Development <dri-devel@lists.freedesktop.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 8/8] drm/fourcc: Add DRM_FORMAT_D1
Date: Thu, 17 Feb 2022 11:42:29 +0100 [thread overview]
Message-ID: <CAMuHMdXf3tFLb16Y=wh5C3QUYN4PdCjaYPCzMOTCye-eYS-N8w@mail.gmail.com> (raw)
In-Reply-To: <20220217121033.0fc7f6ba@eldfell>
Hi Pekka,
On Thu, Feb 17, 2022 at 11:10 AM Pekka Paalanen <ppaalanen@gmail.com> wrote:
> On Tue, 15 Feb 2022 17:52:26 +0100
> Geert Uytterhoeven <geert@linux-m68k.org> 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@linux-m68k.org>
> > --- 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@linux-m68k.org
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
next prev parent reply other threads:[~2022-02-17 10:42 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-15 16:52 [PATCH 0/8] drm: Add support for low-color frame buffer formats Geert Uytterhoeven
2022-02-15 16:52 ` [PATCH 1/8] drm/fourcc: Add DRM_FORMAT_C[124] Geert Uytterhoeven
2022-02-17 9:46 ` Pekka Paalanen
2022-02-15 16:52 ` [PATCH 2/8] drm/fb-helper: Add support for DRM_FORMAT_C[124] Geert Uytterhoeven
2022-02-17 14:57 ` Thomas Zimmermann
2022-02-17 16:12 ` Geert Uytterhoeven
2022-02-17 16:18 ` Simon Ser
2022-02-17 17:21 ` Geert Uytterhoeven
2022-02-17 20:34 ` Sam Ravnborg
2022-02-18 8:14 ` Thomas Zimmermann
2022-02-18 8:53 ` Geert Uytterhoeven
2022-02-15 16:52 ` [PATCH 3/8] drm/fourcc: Add drm_format_info_bpp() helper Geert Uytterhoeven
2022-02-15 16:52 ` [PATCH 4/8] drm/client: Use actual bpp when allocating frame buffers Geert Uytterhoeven
2022-02-17 14:58 ` Thomas Zimmermann
2022-02-15 16:52 ` [PATCH 5/8] drm/framebuffer: Use actual bpp for DRM_IOCTL_MODE_GETFB Geert Uytterhoeven
2022-02-15 16:52 ` [PATCH 6/8] drm/gem-fb-helper: Use actual bpp for size calculations Geert Uytterhoeven
2022-02-15 16:52 ` [PATCH 7/8] drm/fourcc: Add DRM_FORMAT_R[124] Geert Uytterhoeven
2022-02-17 10:02 ` Pekka Paalanen
2022-02-15 16:52 ` [PATCH 8/8] drm/fourcc: Add DRM_FORMAT_D1 Geert Uytterhoeven
2022-02-17 10:10 ` Pekka Paalanen
2022-02-17 10:42 ` Geert Uytterhoeven [this message]
2022-02-17 14:28 ` Pekka Paalanen
2022-02-17 14:35 ` Michel Dänzer
2022-02-17 20:36 ` Sam Ravnborg
2022-02-17 10:11 ` Simon Ser
2022-02-17 20:37 ` [PATCH 0/8] drm: Add support for low-color frame buffer formats Sam Ravnborg
2022-02-18 8:56 ` Thomas Zimmermann
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