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

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Date:   Tue, 18 Apr 2017 12:00:17 +0200
From:   Gerd Hoffmann <kraxel@...hat.com>
To:     Pekka Paalanen <ppaalanen@...il.com>
Cc:     dri-devel@...ts.freedesktop.org,
        open list <linux-kernel@...r.kernel.org>,
        amd-gfx@...ts.freedesktop.org,
        Daniel Vetter <daniel.vetter@...el.com>,
        Ilia Mirkin <imirkin@...m.mit.edu>
Subject: Re: [RfC PATCH] drm: fourcc byteorder: brings header file comments
 in line with reality.

  Hi,

> > 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.
> 
> I wonder if that is just an oversight from trying to match OpenGL
> formats to DRM formats. It's full of gotcha's.
> 
> Did you try with GLAMOR? Do you see a difference with and without
> GLAMOR? Hmm, but you have no GPU support, so GLAMOR would be through a
> Mesa software renderer? I think I heard someone say something about
> Mesa software on BE...

So, did some more testing to see where we stand.

Historical note:  RHEL-6.9 (gnome 2) works fine.  Not of much interest
here, it drives the qemu stdvga with offb, not bochs-drm.

More interesting:  RHEL-7.3 (gnome 3.14) works fine too.  kernel 3.10,
but drm drivers updated to roughly 4.6 level.  Runs bochs-drm.  mesa
11.2.2.  glamour not used.

Most recent:  Fedora 25 (gnome 3.22) looks mostly ok, but there are
rendering glitches, for example in the gnome activities screen (the one
you get when you press the windows key).  kernel 4.10, mesa 13.0.4.
glamor not used, but I think gnome-shell uses opengl (via llvmpipe) for
compositing.

btw: is there some way to start a wayland session from a shell (i.e.
what startx does for xorg)?

cheers,
  Gerd