From: Geert Uytterhoeven <geert@linux-m68k.org>
To: Gerd Hoffmann <kraxel@redhat.com>
Cc: "Michel Dänzer" <michel.daenzer@mailbox.org>,
"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>,
"Noralf Trønnes" <noralf@tronnes.org>,
"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 1/3] drm/fourcc: Add missing big-endian XRGB1555 and RGB565 formats
Date: Tue, 12 Jul 2022 10:43:17 +0200 [thread overview]
Message-ID: <CAMuHMdVhxE9aayG8qRMwUuBryiR_ng08m63_+GY8htFCSmUiWg@mail.gmail.com> (raw)
In-Reply-To: <20220712083907.3ic7bltstaskz72n@sirius.home.kraxel.org>
Hi Gerd,
On Tue, Jul 12, 2022 at 10:39 AM Gerd Hoffmann <kraxel@redhat.com> wrote:
> On Tue, Jul 12, 2022 at 10:01:15AM +0200, Geert Uytterhoeven wrote:
> > > It IMHO is not applicable to any physical hardware. It's used by
> > > virtio-gpu where the supported format depends on the byte order
> > > (it is argb8888 in native byte order). Only virtual hardware can
> > > have that kind of behavior.
> > >
> > > And we can probably drop the DRM_FORMAT_HOST_* variants for 1555 and
> > > 565, they are not used anywhere.
> >
> > Atari DRM supports (big-endian) RGB565, so it uses
> > DRM_FORMAT_HOST_RGB565.
>
> Fixed big endian should use 'DRM_FORMAT_RGB565 | DRM_FORMAT_BIG_ENDIAN'.
True.
> As described above DRM_FORMAT_HOST_RGB565 means bigendian on bigendian
> hosts and little endian on little endian hosts. Which is not correct
> when your hardware does big endian no matter what.
But (a) drm_driver_legacy_fb_format() uses DRM_FORMAT_HOST_RGB565
if quirk_addfb_prefer_host_byte_order is set, and (b)
quirk_addfb_prefer_host_byte_order must be set on big-endian as
per commit eae06120f1974e1a ("drm: refuse ADDFB2 ioctl for broken
bigendian drivers").
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:[~2022-07-12 8:43 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-07-08 18:21 [PATCH 0/3] drm: Endianness fixes Geert Uytterhoeven
2022-07-08 18:21 ` [PATCH 1/3] drm/fourcc: Add missing big-endian XRGB1555 and RGB565 formats Geert Uytterhoeven
2022-07-11 15:22 ` Michel Dänzer
2022-07-11 15:30 ` Geert Uytterhoeven
2022-07-11 16:28 ` Michel Dänzer
2022-07-12 7:47 ` Gerd Hoffmann
2022-07-12 8:01 ` Geert Uytterhoeven
2022-07-12 8:39 ` Gerd Hoffmann
2022-07-12 8:43 ` Geert Uytterhoeven [this message]
2022-07-12 9:03 ` Gerd Hoffmann
2022-07-12 9:09 ` Michel Dänzer
2022-07-12 9:10 ` Geert Uytterhoeven
2022-07-12 8:31 ` Gerd Hoffmann
2022-07-08 18:21 ` [PATCH 2/3] drm/format-helper: Fix endianness in drm_fb_*_to_*() conversion helpers Geert Uytterhoeven
2022-07-08 18:21 ` [PATCH 3/3] drm/gud: Fix endianness in gud_xrgb8888_to_color() helper Geert Uytterhoeven
2022-07-19 14:39 ` Noralf Trønnes
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