From: "Arnd Bergmann" <arnd@arndb.de>
To: "Thomas Zimmermann" <tzimmermann@suse.de>,
"Javier Martinez Canillas" <javierm@redhat.com>,
"David Airlie" <airlied@linux.ie>,
"Daniel Vetter" <daniel@ffwll.ch>, "Helge Deller" <deller@gmx.de>,
"Maxime Ripard" <maxime@cerno.tech>,
sam@ravnborg.org, "Michal Suchanek" <msuchanek@suse.de>,
"Michael Ellerman" <mpe@ellerman.id.au>,
benh@kernel.crashing.org, "Paul Mackerras" <paulus@samba.org>,
"Geert Uytterhoeven" <geert@linux-m68k.org>,
mark.cave-ayland@ilande.co.uk
Cc: linux-fbdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org,
dri-devel@lists.freedesktop.org
Subject: Re: [PATCH v4 5/5] drm/ofdrm: Support big-endian scanout buffers
Date: Wed, 12 Oct 2022 15:12:35 +0200 [thread overview]
Message-ID: <76d8a408-fc3e-4bd1-91c5-8278f7469979@app.fastmail.com> (raw)
In-Reply-To: <0a15ecf5-939d-3b00-bcde-0fc7b449cfda@suse.de>
On Wed, Oct 12, 2022, at 2:00 PM, Thomas Zimmermann wrote:
>
> Could well be. But ofdrm intents to replace offb and this test has
> worked well in offb for almost 15 yrs. If there are bug reports, I'm
> happy to take patches, but until then I see no reason to change it.
I wouldn't change the code in offb unless a user reports a bug,
but I don't see a point in adding the same mistake to ofdrm if we
know it can't work on real hardware.
I tried to find out where this is configured in qemu, but it seems
to depend on the framebuffer backend there: most are always little-endian,
ati/bochs/vga-pci/virtio-vga are configurable from the guest through
some register setting, but vga.c picks a default from the
'TARGET_WORDS_BIGENDIAN' macro, which I think is set differently
between qemu-system-ppc64le and qemu-system-ppc64.
If you are using the framebuffer code from vga.c, I would guess that
that you can run a big-endian kernel with qemu-system-ppc64,
or a little-endian kernel with qemu-system-ppc64le and get the
correct colors, while running a little-endian kernel with
qemu-system-ppc64 and vga.c, or using a different framebuffer
emulation on a big-endian kernel would give you the wrong colors.
Which combinations did you actually test?
Arnd
next prev parent reply other threads:[~2022-10-12 13:14 UTC|newest]
Thread overview: 29+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-09-28 10:50 [PATCH v4 0/5] drm: Add driver for PowerPC OF displays Thomas Zimmermann
2022-09-28 10:50 ` [PATCH v4 1/5] drm/ofdrm: Add ofdrm for Open Firmware framebuffers Thomas Zimmermann
2022-09-28 10:50 ` [PATCH v4 2/5] drm/ofdrm: Add CRTC state Thomas Zimmermann
2022-09-28 10:50 ` [PATCH v4 3/5] drm/ofdrm: Add per-model device function Thomas Zimmermann
2022-09-28 10:50 ` [PATCH v4 4/5] drm/ofdrm: Support color management Thomas Zimmermann
2022-09-28 10:50 ` [PATCH v4 5/5] drm/ofdrm: Support big-endian scanout buffers Thomas Zimmermann
2022-09-28 11:12 ` Michal Suchánek
2022-09-28 11:30 ` Thomas Zimmermann
2022-10-11 7:46 ` Javier Martinez Canillas
2022-10-11 11:30 ` Thomas Zimmermann
2022-10-11 20:06 ` Arnd Bergmann
2022-10-11 21:38 ` Michal Suchánek
2022-10-12 6:29 ` Arnd Bergmann
2022-10-12 7:23 ` Michal Suchánek
2022-10-12 6:46 ` Thomas Zimmermann
2022-10-12 7:17 ` Arnd Bergmann
2022-10-12 7:40 ` Thomas Zimmermann
2022-10-12 7:44 ` Arnd Bergmann
2022-10-12 8:27 ` Thomas Zimmermann
2022-10-12 8:38 ` Arnd Bergmann
2022-10-12 12:00 ` Thomas Zimmermann
2022-10-12 13:12 ` Arnd Bergmann [this message]
2022-10-12 14:27 ` Michal Suchánek
2022-10-13 7:39 ` Javier Martinez Canillas
2022-10-17 6:44 ` Benjamin Herrenschmidt
2022-10-12 14:31 ` Thomas Zimmermann
2022-10-12 14:59 ` Ville Syrjälä
2022-10-12 16:01 ` Michal Suchánek
2022-10-12 12:07 ` Michal Suchánek
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=76d8a408-fc3e-4bd1-91c5-8278f7469979@app.fastmail.com \
--to=arnd@arndb.de \
--cc=airlied@linux.ie \
--cc=benh@kernel.crashing.org \
--cc=daniel@ffwll.ch \
--cc=deller@gmx.de \
--cc=dri-devel@lists.freedesktop.org \
--cc=geert@linux-m68k.org \
--cc=javierm@redhat.com \
--cc=linux-fbdev@vger.kernel.org \
--cc=linuxppc-dev@lists.ozlabs.org \
--cc=mark.cave-ayland@ilande.co.uk \
--cc=maxime@cerno.tech \
--cc=mpe@ellerman.id.au \
--cc=msuchanek@suse.de \
--cc=paulus@samba.org \
--cc=sam@ravnborg.org \
--cc=tzimmermann@suse.de \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).