From: Thomas Zimmermann <tzimmermann@suse.de>
To: Geert Uytterhoeven <geert@linux-m68k.org>,
Gerd Hoffmann <kraxel@redhat.com>
Cc: Helge Deller <deller@gmx.de>, Daniel Vetter <daniel@ffwll.ch>,
Linus Torvalds <torvalds@linux-foundation.org>,
"airlied@gmail.com" <airlied@gmail.com>,
Linux Fbdev development list <linux-fbdev@vger.kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
DRI Development <dri-devel@lists.freedesktop.org>,
Javier Martinez Canillas <javierm@redhat.com>
Subject: Re: [PATCH] MAINTAINERS: Add Helge as fbdev maintainer
Date: Mon, 17 Jan 2022 14:51:07 +0100 [thread overview]
Message-ID: <70530b62-7b3f-db88-7f1a-f89b824e5825@suse.de> (raw)
In-Reply-To: <CAMuHMdW=Zpp2mHbrBx7i0WN8PqY3XpK5qpyAyYxgf9n88edpug@mail.gmail.com>
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Hi
Am 17.01.22 um 14:29 schrieb Geert Uytterhoeven:
> Hi Gerd,
>
> On Mon, Jan 17, 2022 at 1:57 PM Gerd Hoffmann <kraxel@redhat.com> wrote:
>>> b) to include new drivers (for old hardware) if they arrive (probably happens rarely but there can be).
>>> I know of at least one driver which won't be able to support DRM....
>>
>> Hmm? I seriously doubt that. There is always the option to use a
>> shadow framebuffer, then convert from standard drm formats to whatever
>> esoteric pixel format your hardware expects.
>>
>> Been there, done that. Have a look at the cirrus driver. The physical
>> hardware was designed in the early 90-ies, almost 30 years ago. These
>> days it exists in virtual form only (qemu emulates it). Thanks to the
>> drm driver it runs wayland just fine even though it has a bunch of
>> constrains dictated by the hardware design.
>
> The Cirrus DRM driver supports TrueColor (RGB565/888 and ARGB8888)
> modes only. The Cirrus fbdev driver also supports mochrome and 256
> color modes.
>
> There exist some DRM drivers that do support DRM_FORMAT_C8, but none of
> the "tiny" ones do. Same for DRM_FORMAT_RGB{332,233}. Using a shadow
> frame buffer to convert from truecolor to 256 colors would be doable,
> but would give bad results. And what about less colors?
> Adding support for e.g. DRM_FORMAT_C4 is not straight-forward, as
> the DRM core assumes in many places that a pixel is at least 1 byte,
> and would crash otherwise (yes I tried). Other modes needed are
> DRM_FORMAT_Y4 and DRM_FORMAT_{BW,WB} (monochrome).
We export XRGB32 from each driver, because userspace expects it. But
that is not a hard requirement. Userspace can use any format. It's just
that no one seems to have any use cases so far, so no work has been
done. Think of XRGB32 as a fallback.
Personally, I'd much appreciate if userspace would support more of the
native formats and not rely on XRGB32.
> This not only to support "old" hardware, but also modern small OLED
> and e-ink displays.
There's a DRM driver for Repaper e-Ink displays. So it seems doable at
least.
Best regards
Thomas
>
> On the positive side: DRM would force e.g. the Amiga and Atari
> bitplane formats to become internal to the kernel driver, with the
> kernel driver converting from packed pixels to bitplanes. Hence
> userspace would no longer have to care about bitplanes.
>
>
> 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
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Maxfeldstr. 5, 90409 Nürnberg, Germany
(HRB 36809, AG Nürnberg)
Geschäftsführer: Ivo Totev
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next prev parent reply other threads:[~2022-01-17 13:51 UTC|newest]
Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-01-14 18:11 [PATCH] MAINTAINERS: Add Helge as fbdev maintainer Helge Deller
2022-01-14 18:31 ` Geert Uytterhoeven
2022-01-17 9:48 ` Daniel Vetter
2022-01-17 10:02 ` Daniel Vetter
2022-01-17 10:19 ` Javier Martinez Canillas
2022-01-17 10:49 ` Jani Nikula
2022-01-17 10:57 ` Helge Deller
2022-01-17 12:15 ` Helge Deller
2022-01-17 12:57 ` Gerd Hoffmann
2022-01-17 13:29 ` Geert Uytterhoeven
2022-01-17 13:51 ` Thomas Zimmermann [this message]
2022-01-17 14:10 ` Geert Uytterhoeven
2022-01-17 14:47 ` Helge Deller
2022-01-17 15:03 ` Daniel Vetter
2022-01-17 20:17 ` Helge Deller
2022-01-18 6:29 ` Gerd Hoffmann
2022-01-18 8:10 ` Geert Uytterhoeven
2022-01-18 11:44 ` Daniel Vetter
2022-01-18 14:23 ` Thomas Zimmermann
2022-01-18 14:39 ` Simon Ser
2022-01-20 12:50 ` Gerd Hoffmann
2022-01-21 8:55 ` Daniel Vetter
2022-01-24 18:38 ` Geert Uytterhoeven
2022-01-24 18:50 ` Daniel Vetter
2022-01-24 19:05 ` Thomas Zimmermann
2022-01-18 8:20 ` Helge Deller
2022-01-18 9:16 ` Gerd Hoffmann
2022-01-18 10:13 ` Helge Deller
2022-01-18 10:44 ` Helge Deller
2022-01-18 12:48 ` Gerd Hoffmann
2022-01-17 15:05 ` Thomas Zimmermann
2022-01-17 16:05 ` Helge Deller
2022-01-17 14:53 ` Thomas Zimmermann
2022-01-18 6:11 ` Gerd Hoffmann
2022-01-18 8:09 ` Helge Deller
2022-01-17 15:00 ` Daniel Vetter
2022-01-17 15:42 ` Helge Deller
2022-01-17 15:56 ` Daniel Vetter
2022-01-17 15:58 ` Thomas Zimmermann
2022-01-17 16:21 ` Helge Deller
2022-01-17 16:38 ` Daniel Vetter
2022-01-17 17:19 ` Helge Deller
2022-01-17 19:45 ` Helge Deller
2022-01-17 21:55 ` Ilia Mirkin
2022-01-18 11:14 ` Daniel Vetter
2022-01-18 14:14 ` Thomas Zimmermann
2022-01-17 21:40 ` Jani Nikula
2022-01-17 21:44 ` Helge Deller
2022-01-18 8:38 ` Jani Nikula
2022-01-18 8:41 ` Geert Uytterhoeven
2022-01-18 11:41 ` Daniel Vetter
2022-01-18 12:11 ` Simon Ser
2022-01-18 8:54 ` Helge Deller
2022-01-18 9:33 ` Javier Martinez Canillas
2022-01-18 9:45 ` Geert Uytterhoeven
2022-01-18 11:18 ` Daniel Vetter
2022-01-18 11:42 ` Helge Deller
2022-01-18 8:41 ` Helge Deller
2022-01-18 9:12 ` Helge Deller
2022-01-17 11:16 ` Thomas Zimmermann
2022-01-17 11:33 ` Helge Deller
2022-01-17 12:13 ` Thomas Zimmermann
2022-01-17 18:47 ` Sven Schnelle
2022-01-18 8:33 ` Pekka Paalanen
2022-01-18 9:53 ` Gerd Hoffmann
2022-01-18 11:22 ` Daniel Vetter
2022-01-18 12:07 ` Gerd Hoffmann
2022-01-19 8:39 ` Pekka Paalanen
2022-01-20 9:06 ` Geert Uytterhoeven
2022-01-20 11:32 ` Daniel Vetter
2022-01-20 12:13 ` Geert Uytterhoeven
2022-01-20 12:33 ` Daniel Vetter
2022-01-20 12:46 ` Geert Uytterhoeven
2022-01-24 18:50 ` Geert Uytterhoeven
2022-01-24 19:37 ` Daniel Vetter
2022-01-20 11:51 ` Gerd Hoffmann
2022-01-18 8:58 ` Michel Dänzer
2022-01-18 10:05 ` Sven Schnelle
2022-01-18 14:06 ` Thomas Zimmermann
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