linux-kernel - Re: [RfC PATCH] drm: fourcc byteorder: brings header file comments in line with reality.

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Message-ID: <CAKb7Uvgidg9_RkU0NJY7qwhcf0_Hyc0EGzWmvk0qqaf_YDW97g@mail.gmail.com>
Date:   Mon, 10 Apr 2017 10:45:26 -0400
From:   Ilia Mirkin <imirkin@...m.mit.edu>
To:     Gerd Hoffmann <kraxel@...hat.com>
Cc:     Pekka Paalanen <ppaalanen@...il.com>,
        Daniel Vetter <daniel.vetter@...el.com>,
        amd-gfx@...ts.freedesktop.org,
        open list <linux-kernel@...r.kernel.org>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>
Subject: Re: [RfC PATCH] drm: fourcc byteorder: brings header file comments in
 line with reality.

On Mon, Apr 10, 2017 at 10:17 AM, Gerd Hoffmann <kraxel@...hat.com> wrote:
>   Hi,
>
>> which software have you used as representative of "reality"?
>
> ppc64 (big endian) virtual machine, running with qemu stdvga & bochs-drm
> driver.  Xorg with modesetting driver uses DRM_FORMAT_XRGB8888 (one and
> only format supported by bochs-drm), and we have to interpret that in
> bigendian byte order on the host side to get a correct display.
>
> Didn't try wayland.  Can do, but will take a while.  Don't have a
> wayland-capable guest install at hand, and installing one takes a while
> because I don't have a physical pseries and emulation is slooooww.
>
>> To solve that problem, we would like to know if anything existing would
>> break for each possible solution, but no developers using BE have really
>> turned up.
>
> That is part of the problem.
> And even ppc is moving to little endian these days ...

The poor saps who are still using PPC G4's and G5's with NVIDIA and
ATI boards constantly get their working setups broken by people trying
to "fix" BE. I think it's important to keep them in mind, and test
those setups, whenever one tries to make a large sweeping change.

Cheers,

  -ilia