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

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Date:   Mon, 17 Apr 2017 02:43:44 -0400
From:   Ilia Mirkin <imirkin@...m.mit.edu>
To:     Pekka Paalanen <ppaalanen@...il.com>
Cc:     Gerd Hoffmann <kraxel@...hat.com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        open list <linux-kernel@...r.kernel.org>,
        amd-gfx@...ts.freedesktop.org,
        Daniel Vetter <daniel.vetter@...el.com>
Subject: Re: [RfC PATCH] drm: fourcc byteorder: brings header file comments in
 line with reality.

On Tue, Apr 11, 2017 at 10:18 AM, Ilia Mirkin <imirkin@...m.mit.edu> wrote:
>> However, I totally agree with Alex that someone with a BE machine
>> should review the whole stack before we could be confident with anything.
>
> Here's what I'm confident about: xf86-video-nouveau worked just fine
> on top of kernel 4.3 on an AGP GeForce FX 5200 (with AGPGART turned
> off because ... well ... uninorth). fbcon/fbdev accel worked,
> xf86-video-nouveau's 2d accel worked, and simple demos (ala glxgears)
> worked after I fixed up mesa and nv30 driver items in version ... 11.1
> it seems. As I recall it had gotten all broken in 10.0 or so by Adam
> Jackson in the name of making llvmpipe work on BE, declaring all other
> drivers broken, with various fixes by Michel Dänzer to get it back to
> working over the years.
>
> Anyone "fixing" the stack has to maintain that level of functioning
> through their various fixing.
>
> I will double-check that the above still works with the latest
> kernel/xorg/xf86-video-nouveau/mesa and report back (hopefully by this
> weekend). If there are any patches you'd like me to test, now's the
> time to ask -- getting the box up and running is the hard part,
> booting up an extra kernel -- easy.

OK, so I revived my PowerMac7,3 G5 setup (PPC64 BE, NV34 GPU). Booted
it with an upstream 4.11-rc7 kernel, loaded up the nouveau kernel
module (which is included in that kernel), updated X to 1.19.2 and
mesa to 17.0.3. Everything works fine. Specifically:

fbcon on top of fbdev provided by nouveau -- colors are fine
glxgears hw-accelerated by mesa on top of xf86-video-nouveau using
DRI2 -- colors are fine
glxgears softpipe-accelerated by mesa on top of xf86-video-nouveau --
colors are fine
glxgears softpipe-accelerated by mesa on top of xf86-video-modesetting
-- colors are fine
xterm on top of xf86-video-nouveau -- colors are fine
xterm on top of xf86-video-modesetting -- colors are fine

I couldn't test anything with GLAMOR since GLAMOR requires GL 2.1 or
higher, whereas nouveau's NV3x acceleration only provides GL 1.5 (due
to lacking NPOT and a handful of other things).

The modetest utility did have trouble with AR24 and I'm pretty sure
the XR24 pattern was off too. However I wouldn't be surprised if the
modetest utility itself had endian issues in the pattern generation
logic. (Seems to be the case, based on a quick glance at the
tests/util/format.c logic and how it's used in pattern.c.)

So in short, I think the current definitions of format are fine.

Cheers,

  -ilia